This article contains an engine comparison chart and conversion notes, and explains the differences and interchangeability between parts and which are more suitable for modifying your 240Z, 260Z or 280Z.

Some of the areas discussed include: carburetors, distributors, coils, spark plugs and plug wires, cams, rocker arms, headers, mufflers, exhaust pipes, air cleaners, transmissions, differentials, clutches, fly wheels, tachometers, speedometer calibration, oil pumps, lubrication and additives.

 

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Datsun was very clever using the same 6-cylinder engine/transmission and drivetrain platform from 1970 to 1983. Not only did this make them easy to manufacture, but it lets an enthusiast mix parts from different years to create the perfect first generation Z. The secret is that the heavier 280ZX used physically identical L28 engines and transmissions from '79 all the way through 1983, making them simple bolt-ins into earlier Z models. And since a great many 280Z's and ZX's are in junkyards, what better time to breathe some life back into your car? So here is my formula for a very quick and fun 1970-78 Z, along with tested performance tips. 240-260 folks would want to swap everything, while 280Z and ZX people would should keep their injection and ignition and change the drivetrain parts only.

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FIRST - The Car

Unlike Chevy Chevelles of which several million were made, there are probably only a few thousand running 1970-78 Zs left. Rust, wrecks, and rebuilds have sidelined most of them over the decades. And despite the nostalgia, I don't see a problem removing the old engine and drivetrain and replacing them with newer versions. Without your intervention the car would likely never see the street again. So there's nothing wrong with restoring it the way you want, it's your car.

If you want to find a base model to use for your fantasy racer, try to find one of the first 12,000 or so 240Zs made from 1970 to early 1971. These are identified by a "solid" B-pillar with a "240Z" badge behind the side window, and two grills on the rear hatch. These '70-71s were the lightest of all ZCARs, at about 2200 lbs, making them the best for performance buildups. Later models went to the Z badge and removed the hatch grills. Unfortunately the weight went up a few hundred pounds too.

 

SECOND - The Engine

Datsun made several blocks over the years, varying in bore and casting methods. Compared to the L24, the L26 had a longer stroke, while the L28 had both a longer stroke and a larger bore. The way to identify the block is to look on the driver side of the engine, to the right of the motor mount. That's where they cast the block number.

ENGINE CASTING CODE

L24 (1970 240Z) #E31 (flat-top pistons)

L24 ('71-73 240Z) #P30 (flat-top pistons)

L26 ('74 260Z) #P30 (flat-top pistons)

L28 ('75-80 280Z) #N42 (dished pistons)

L28 ('81-83 280ZX) #F54 (flat-top/dished pistons, siamesed cylinders)

Except for the turbo guys, it seems that only since the late '90s have people been focusing on the F54 engines. I think the reason is that when Zcars were popular for racing in the late '70s and early '80s, the ZX motors were not available in junkyards. And people probably thought: "...why would I want a slow ZX motor". What they didn't realize is that minus power steering, AC, and other ZX plumbing, the F54 is the most powerful and refined of the L-series engines. It was Nissan's final evolution of the Z engine, with more horsepower and torque than earlier motors...it had to be to carry the heavier ZX. Personally, I like the idea of putting a late model F54 in a first generation Z, and converting it back to carbs. Very retro, but totally functional and quick.

So if you want to install the best motor in your Z, go for the last of the L28's, the 1981-1983 F54. It's cylinders are "siamesed" meaning that instead of coolant flowing between all the cylinders as on earlier models, they are connected between 1-2, 3-4, 5-6 with cast webbing for more rigidity. In addition, all Datsun did to make the F54 a turbo motor was to replace the flattop pistons with dished ones ( to lower compression), and add a turbo head with better exhaust ports and a goofy distributor. So there really isn't a "turbo block", the substitution of pistons and head are what created the different motor.

It can be tricky determining exactly what's in a car you find, as many have been rebuilt and had the head swapped over the years. First check the block code, and then the head code between the 1st and 2nd spark plugs. Check out the head page to see which head came with which block. Sometimes you have to do a little detective work to figure out what you have.

COMMENTS:

PISTONS The F54 motors with P79 heads ('81-83) have flat-top pistons. All other L28 motors(N42,N47,P90, P90a) came with dished pistons. In a performance engine, flattop pistons create a higher-quench mixture and allow for higher performance combustion chambers. Dished pistons are usually used to lower emissions.

HEADS The P79, P90 and P90a heads are the three heads found on ZX F54 blocks, and have the same chamber volume and dimensions (53.5cc). The P79 has round exhaust ports with steel liners that heat red-hot to reduce emissions, some say they reduce flow, but I've pulled a 13.9 1/4 mile with my carbureted P79, so it can't flow too badly.
My guru racer buddy says Nissan finally "got it right" on the P90, and he feels it's the best flowing head out there. I have to agree, I just modified one this year, and it's design incorporates the best features of all the heads: square exhaust ports, high-quench chambers, and steel seats. Check out my P90 and P79 pages for more modification details.

HORSEPOWER A lot of factors affect horsepower, and it's best not to fixate on numbers. But as a baseline the '75-80 motors put out about 135 net, the '81-83 motors 145 net. BTW, the little plate on the shock tower in the 75-78 280Z's engine compartment says 170hp SAE which is really 135 net.

 

THIRD - Carburetion

The optimum air/fuel ratio for all car engines is something like 14:1. Either the mixture and intake flow is correct for the engine demands, or it isn't... one of the most common mistakes on any high-performance motor is to over-carburete. You see guys putting Holly Dominator 1150 carbs on a stock 5.0 V8, and wonder why it runs badly.

Luckily the stock 240Z Hitachi SU is a great carb for both street and performance, and automatically meters the gas depending on the airflow through it. So whether you are stock or have a cam with large duration, with the proper needle the SU carb tries to keep the correct mixture from idle to redline. A simple, accurate design.

The "good" SU's were from 1969-1973 and will have 4 or 3 screws holding down the domed piston depending on which year it was made. The year makes no difference for performance, as the nozzles and needles from different years interchange. If you have carbs with the square choke flap in the inlet or flat tops then you have the diseased 260Z emission carbs. Exchange them for earlier SU models.
A buddy of mine has a Mikuni 6-pak which runs great flat out, but he has had to spent a lot of time tuning them, very finicky. So for street performance and autocrossing I would stick with SUs.

CARB INTAKE MANIFOLDS

A 240/260 carb intake will bolt right up to any L28 head. The bolt size is 8mmx1.25.

The 1970-73 used the E88. I've heard of another (E36?) but never seen it.
The 1974 260Z used the N36. This intake manifold is rumored to produce 10hp more than the 240 one. If it's true, simply bolting it on a stock motor probably wouldn't do much. A modified motor that needs more flow would benefit more: if it's true.

The manifolds are actually 2-piece: left and right, with a water line connecting them. Supposedly the water line is dual purpose, keeping the manifolds cooler (since they sit over the exhaust) and also warming the intake more quickly during startup. However, I don't see any performance reason for removing the water lines, as they keep the intake temperature stable. Sitting over the exhaust and connected to the block they get pretty hot.

BALANCE TUBE

I've used both 240 and 260 types. The 260Z ones were monstrosities with lots of ports and hose connectors. The 240Z one is simpler with only a couple of vacuum ports. There is a Euro balance tube available which looks very nice. May not work with some carb linkages though.

All the tube does is allow a central spot for brake booster hose, vacuum hoses, and PVC hose to vent. I'm not sure why people think blocking it off from the manifold will somehow increase horsepower, all that does is ruin brake vacuum. You want the PCV valve hose to vent into it, otherwise you will dirty up the inside of the block with combustion by-products. However, make doubly sure the gaskets under each end are sealed tight as a drum since the gaskets get squashed after 30 years: Permatex makes a great roll of gasket material you can use to make cut your own.

NOZZLES AND CARB NEEDLES

The '70-71 240 used "N27" needles and related nozzles.

The '72 manual trans car used N54 needles, the '72 automatic used N58, both with the same '72 nozzles.

The '73 nozzles/needles were emissions designs, not recommended for performance.

SM needles from British SU's are excellent for performance.

My own setup is 1970-'71 nozzles, SM needles on a set of 1970-'72 carbs, 260Z "N36" intake.

Buy new rubber bushings from the dealer to hold the SU float bowls to the carbs, make sure they're snug and level.

Keep the stock fuel return rail and use an aftermarket electric fuel pump with 3-5 psi. Higher pressure can overpower the needle valves, lower causes the bowls to run dry on heavy acceleration. Don't use an injection fuel pump with carbs (30+psi, too high.) A junk-yard solution is to get a pump from a early 1980's Mazda RX-7, it puts out 5PSI.

Always mount an electric pump as close to the gas tank as you can. It's better to "push" the gas rather than "pull".

Look in Motorsport Auto or Victoria British catalogs for recommended pumps. The Purolator brand electric pumps are reliable I'm told, but are very noisy.
Remove the little copper mesh filters in the SU float bowl inlets. These can restrict flow. I have a Purolator "clear" fuel filter installed where the hose comes off the firewall. This is easy to inspect and clean.

Retain the water cooling through the intake manifold.

Don't block off the PCV hoses. It's important that the crankcase be vented to the intake so the motor stays clean. Using a little K&N breather on the valve cover looks cool, but stinks the car up with fumes.

On 240s, keep the "flow-valve" on the driver fender well connected. This pulls fumes from the gas tank and burns them in the carbs.

 

FOURTH - The Transmission

Borg T5 and lightened 240mm turbo flywheel.

Datsun seems to have used three 5-speeds for U.S. Z cars:

One from '77-80
One from '81 to 83
A Borg-Warner T5 in 1983

My page on installing a Borg-Warner T5 in a 1st generation Z. Nissan called the '77-80 trans a "wide ratio", while the '81-83 is called a "close ratio" 5-speed. The early one has the lowest 1st/2nd gears for acceleration, but a wide spread between 2nd and 3rd. The later one has a taller 1st/2nd but a tighter spread between 2nd and 3rd. It also has a much taller 5th for cruising. Your choice.

According to a Z Doc friend who rebuilds transmissions, the early 5-speed is a 4-speed with 5th and reverse sharing the same fork. He said it's common for people to "blow" 5th gear as the fork is weaker. He said the later 5-speed is a genuine 5-speed and is stouter. I call the early one a 280a and the later a 280b to keep them straight.

Keeping the Speedometer Correct

Everyone gets confused about how to calibrate the speedometer after swapping differentials, it's actually very easy. The speedometer is metered by a plastic, toothed cog on the end of the speedometer cable that screws into the transmission. This cog is paired with the differential, not the trans. So it doesn't matter which trans you have, all you do is select the proper cog for the rear-end ratio you have in the car. While they are colored for easy identification, the Nissan dealer only has them in their part list as "17, 18, 19, 20, or 21" tooth cogs. Here's how to figure out which is which:

YELLOW is the 16 tooth for the 3.36
BLACK is the 17 tooth for the 3.54
BLUE is the 18 tooth for the 3.70
WHITE is the 19 tooth for the 3.90
RED is the 20 tooth for the 4.11
PURPLE is the 21 tooth for the 4.38

~Don't rely on a junkyard Zcar to have the right colored cog~
~When in doubt, count the number of teeth, the color doesn't matter~

NOTE: Hard to describe online, but there are 2 different cog bodies that hold the cogs, a '75-80, and '81-83. These bodies have different cog "offsets". If you look closely in the picture above, notice how the red cog is offset to the right, and the blue to the left. This means you must keep the body with the trans it came in, and only swap the cog. Otherwise the cog won't mesh the proper way inside the trans.

In other words, if you have a '75-80 trans, you must use the '75-80 body and swap on the white (or other) cog of your choice. If you have a 1981-83 trans, use the later cog body. It's easy, just drive a small pin out to change the cog.

The weird one is the larger red 4.11 cog, which requires a later ZX sleeve to fit into the older '77-'80 trans (I tried it). But will it fit into a later 280b? I don't know, I use a white cog in mine for now.

On 240's, you will have to cutout about 2 inches of metal from the front/right edge where the shifter goes through the trans tunnel when using a 5-speed. Otherwise the throw into 5th gear will hit. This cutting is the price of a 5-speed trans, and is not a big deal at all, the console covers it.

 

FIFTH - The Flywheel and Clutch

This is a 2+2 flywheel and clutch. [picture omitted]

Measure the width of your flywheel's shiny clutch contact surface.

If it's 225mm wide then you have a coupe version which uses a 550lb pressure-plate.

If it's 240mm wide then you have a 2+2/turbo version with a 780lb plate and a wider disc.

Both flywheels are the same at weight at 23 lbs, and the diameter is the same (only the contact area is wider). But a turbo pressure plate and disc clutch are definitely heavier than coupe version by a few pounds. So how much performance is actually lost with a heavier assembly? A good one to argue at Z meetings...

I haven't tried any of the competition clutches, but truthfully the only time you really need a stronger one is if your engine torque is causing the clutch to slip. I agree it sounds neat to say your car has a "competition clutch", but it doesn't make the car faster. I autocross and dragrace my Z, and my stock clutch works fine (really) after 2 years (Zoom brand). A buddy has a Centerforce 2 which feel very solid, but rumor has it the Centerforce One is a stock clutch with only extra weights hanging on the pressure plate fingers.

LIGHTER FLYWHEEL

Used for decades to reduce drag on the engine and to make it spin up faster. It won't make the engine develop any more horsepower internally, but can cut down on parasitic drag. Better for track racing than dragracing, as on smaller engines the rotational inertia that helps the car off the line is reduced. This loss of inertia can make the engine rev down quickly between shifts. Some people consider them undriveable on the street, because the engine can stall easily, especially when cold. On motorcycles, having a too-light flywheel can make it stall between shifts(!) So keep this tradeoff in mind if you want one for your car.

CONVERSION NOTES:

There are 2 versions of flywheels on all '75-83 motors: coupe and 2+2/turbo. 23 lbs each.

Coupe and 2+2 clutches aren't interchangeable because the pressureplate dowel holes won't match the flywheel dowels.
You can use a Z 5-speed on any year Z block, and any year L28 clutch can be used, but the throwout bearing "collar" must match the style of the flywheel (coupe or 2+2). In other words, if you have a 2+2 flywheel, you need to change the throwout collar to a 2+2 version when using a coupe trans. And vice-versa.

Auto trans engines have a 1/4" metal spacer between the driveplate and crankshaft, remove this when adding a flywheel.
A pilot bushing needs to be installed in the crankshaft if using an auto trans engine (they didn't get one).

Unless you need the accessories, don't use a big 3-row harmonic balancer in front, get rid of it. Compared to a 280Z 2-row it weighs about 5lbs more. I've read that taking 10lbs off a 10" rear flywheel is the equivalent of taking 207lb off the front of the car. So I believe removing 5lbs from the front of the crankshaft is desirable. Also, I've been told the 3-rows like to break up over 6,000rpm.

All L28 balancers have identical TDC timing marks and are interchangeable.

 

SIXTH - The Differential

4.11 from 200SX turbo, freshly painted. [picture omitted]

There were three different Zcar R-200's ratios from 1975-83, none were limited slip until 1987. Most 280ZX automatic transmission cars came with an R180, so if you want to find a 3.90 look for a 1981-83 5-speed in the junkyard. Don't try to analyze the confusing table in the Haynes manual, this is the easy way to do it:

Datsun R-200 list (not R180)

'75-79 280Z(X)s had a 3.54
'81-83 turbo ZX's had a 3.54
'81-83 non-turbo ZX's had a 3.90
The '85-86 200SX turbo had a 4.11
The '87-89 LSD was a 3.70

I believe there was also a 3.70 open differential in one of the '79-80 280ZXs. And I've heard a 4.38 R180 came in one of the older Datsun 720 4x4 trucks. But considering the offroad use, the 4x4s probably all rusted out 10 years before the Z did. I've never even seen one on the road.

If you want performance get the R200 out of a junkyard '81-83 5-speed, NON-turbo ZX (3.90). If you're speed freak like me use the 4.11 out of the 200SX turbo. The '85-86 200SX turbos came with a R200, while the non-turbo models I've seen have a solid rear axle. A 4:11 can be found by checking salvage yards and are not LSD differentials, but can make your Z a real rocket off the line. It came with CV halfshafts which aren't needed, use regular Zcar R200 halfshafts on a 4:11 in a first generation Z. Also, some 240SXs came with a finned rear cover. Don't be fooled into thinking this is limited-slip, it's not.

1975 NOTE: 1975 R200s and driveshafts came with unique rear driveshaft/differential flanges. So if you plan on doing a later R200 swap into a 1975 280Z, you will need to use a 1976-78 driveshaft with a 3.90 or 4.11.

BTW: to get R200 halfshafts out, DON"T pry them out or spend an hour unbolting the differential-side flange. Simply unbolt the wheel end, and "yank" the halfshaft hard a few times. A little circlip in the diff holds it but it will pop right out, the yanks don't hurt it. NOTE: sometimes halfshafts in the junkyard refuse to come out even with this method. To get them back in, you have to rotate it around as the shaft clicks into the differential in only one position. You can lock it in place by hitting the tire end with a mallet.

LIMITED SLIP DIFFERENTIALS

Despite the performance of the Z, Nissan only made a limited slip diff very late in the Z's life.

They made 2 types, a standard LSD, and one with a viscous internal drive. The 1987-89 Turbo 300ZX's had the "good" 3.70 LSD, and can be identified by it's finned rear cover. This cover needs to be replaced with the smooth R200 cover to fit properly to the 280Z mustache bar, and the front driveshaft flange on the diff. needs to be replaced with the one your driveshaft uses.
The '88 white SE 300ZX came with the oddball "viscous-drive" R200, and can be identified by a sticker on the driver-side of the diff that says "VISCOUS LSD". This fits a Z, but R200 halfshafts don't lock into them without some fabrication of new halfshaft fittings.

TO DETERMINE THE RATIO (internally)

If you're not sure which ratio R200 you have lying around the garage, check it this way:

Remove the rear plate (drain the oil of course). Then rotate the large ring gear until you see some numbers stamped into the edge facing you.

If it's a 3.54 it will read "39:11"
If it's a 3.70 it will read "37:10"
If it's a 3.90 it will read "39:10"
If it's a 4.11 it will read "37:9"

The first number marks the number of teeth on the large ring gear, the smaller is the number of teeth on the pinion gear connected to the driveshaft. Someone suggested swapping ring and pinions around to create the ratio of your choice. I checked with my buddy the Z Doc, and he said it's very difficult to get the preload and tooth geometry setup properly (he tried it). Oh well.

QUESTION THOUGH: Since the 3.70 and 3.90 apparently use the same 10 tooth pinion, I wonder if a 3.90 ring could be swapped onto a factory limited-slip assembly? This would make a "factory" 3.90 limited slip!

GEAR OIL REFILLING TIP: Instead of uninstalling the differential, I remove one halfshaft and add the oil though the side of the case. Easy.

 

SEVENTH - Ignition

BEWARE THE BAD DISTRIBUTOR CAP!!

For a while I had been getting a strange stumble when accelerating from low revs or at odd places in the rev range. Also, my tach needle (Autometer 5") would jitter at PART throttle but not at full throttle. Weird. I checked all my grounds, rerouted all the wires from my MSD 6A ignition to prevent RFI, measured resistance on all plug wires, and rebuilt the distributor. I even got a new alternator, but no solution.

I finally discovered that my fairly new distributor cap (Borg-Warner, brass terminals) had a ring of brass powder running between the terminals...CROSSFIRING!

Interesting how the tracking seems to follow almost a magnetized path around the terminals. MSD type ignitions are said to produce heavy ionization in the top of a cap, drilling a couple of holes near the top will alleviate it. I had the holes drilled, but my rotor was slightly loose, I suspect that it may have slightly ground into the terminals and the residual ionization distributed the particles. I replaced the cap with a new one...the engine is smooth as silk now, startup instantaneous and tach perfect. An interesting lesson to be learned ...

POINTS vs ELECTRONIC IGNITION

Points distributors are an obsolete technology when it comes to high performance engines. The reason is that Dwell (the amount of time the points stay open) changes if there is even a tiny bit of play in the distributor shaft. Dwell directly affects ignition timing, so any slight rocking back and forth of the shaft puts your ignition timing all over the place...not good on a motor with high compression.

Electronic distributors are usually rock-solid when it comes to timing. Shaft play can still cause slop in the distributor, but generally doesn't cause the timing to fluctuate the same way.

Nissan made 3 electronic ZCAR distributors from 1975-'83, I call 'em D1,D2,D3

D1 came on '75-78 cars. It came with 1 or 2 internal magnetic pickups inside.
This distributor uses a magnetic reluctor and pickup to send a strong pulse to the FI brain underdash, which fires the coil. This is considered a "Magnetic Trigger" distributor.

D2 came on '79-83 cars. It came with a built-in ignition module on the side
This uses a magnetic reluctor wheel and small pickup coil to send a pulse to the ignition module on the side of the distributor, which fires the coil. A simple, self-contained ignition system. Pre-1981 models used the E12-80 IC module, '81-83 models used the E12-92.

D3 came on '81-83 turbos. It uses the FI brain and a crank-firing system.
These require the turbo FI brain and several sensors, I doubt if it could be wired into any other Z without a lot of trouble.

Nissan made two ZCAR distributor IC modules from 1979-'83.

E12-80 1 top plug (2 terminals). Used on 1979-7/80 ZX, Maximas, B210.
This module works best on carbureted motors. The dwell curve is preset into the module, it only needs the distributor and coil to function.

E12-92 1 top plug, 1 side plug. Used on 8/81-83 ZX's, Maximas

According to the shop manual, the 2nd plug on the side is for a spark advance signal from the brain and other sensors. I found when using a E12-92 in place of a E12-80 it automatically retards the timing 8 degrees, most likely because there is no input to the side plug. Even setting the time back to stock leaves the engine feeling very sluggish, so I don't recommend it on carbureted motors. If your car is fuel injected and came with the module, great. If you want to swap a ZX distributor into a carbureted motor, use the E12-80.

WIRING A 280ZX DISTRIBUTOR INTO A 240Z:

This mod converts a 240Z to an ZX electronic distributor. It's not needed on a 280Z or ZX which already have elctronic ignitions.

Find a 1979-1983 280ZX distributor, any year body can be used. But if it's '81-83 it will have the E12-92 module, you will need to locate a E12-80 to replace it.

Remove and clean the metal rear of the IC module so it can ground itself to the side of the distributor.

Remove the triangular hold-down plate on the base of the distributor. Burnish it, as well as the spot where it contacts the distributor and replace...this helps everything ground well to the block. Note that the hold-down plate rotates, you may need to play with the position to get the proper timing mark range you want.

Use quality spade lugs and wire with TIGHT crimps, and solder the wire to the spade connections if possible. Don't solder or crimp onto the E12-80, just make sure the spades fit on tight.

You will need to buy a later distributor base for the front cover if this is a 240Z. Motorsport Auto carries them, fairly cheap.

A 240 tach may not work with this setup since it's inductive pickup can no longer connect to the coil. Replace it with a 75-78 280Z tach and connect the tach sensor lug to the - terminal on the IC module. If the tach jumps around, solder a 7500-10,000 ohm resistor inline with the sensor wire to reduce the signal voltage. If it still won't work buy a Autometer #3990 black face tach.

WARNING: If you have a MSD or Crane, DON'T hookup the module or tach directly to the coil. The 450 volts can fry it. Follow the ignition's hookup guide.

ALTERNATOR UPGRADE

Old news, but the teeny 40 ampere alternator and mechanical voltage regulator that came in the 240Z are marginal, especially when using an electronic ignition system. If you're not an electrical guru, here's the basic explanation:

CURRENT is the amount of voltage 'draw' that your electrical system pulls from the battery or alternator. Every electrical item from your gauges, to dashlights, to the ignition, draws this current rated in amperes or "amps". When the engine is running, the alternator supplies the electricity for the car. So the manufacturer simply adds up the total amperage that electrical items in the car use, and installs an alternator with enough current to supply everything. If everything in the car draws 30 amps when used, you would likely get a 40 amp alternator.

In the early 1970's a stock 240Z only needed an AM radio, points ignition, basic lights, and was given a tiny 40 amp alternator. But today you add an MSD type ignition, a big car stereo amp and flamethrower headlights, and you easily pull several times as much current as the stock alternator can supply. In addition, the Voltage Regulator on the firewall is an external "mechanical" type with points inside that open and close just like on a distributor. Mechanical regulators have been obsolete for 30 years. Nissan went to internally regulated alternators for a reason.

On my 240 the tip-off was that my ammeter needle would jitter at idle. Even more obvious was that at night my dash lights would dim when I neared redline. After spending hours checking grounds and cleaning connectors, I finally decided to get rid of my vintage setup. You could install a monster alternator that puts out 120 amps made by other manufacturers , but an easier route like everything on this page is to use the one that Nissan made. The 1981-'83 non turbo 280ZX came with a 60 amp alternator, the turbo with a 70 amp. I haven't tried the turbo version but the non-turbo version swaps right over. There is a "P" connector on the new alternator which isn't used, just ignore it.

 

THE MOD FOR 240Zs only:

Buy a new "1981-83 Nissan 280ZX non-turbo" alternator at the auto store. Replace the original alternator and follow the directions below. Before you start, fabricate two little wire "jumpers" (cut a wire about 3 inches long, strip the ends, and solder/crimp a male spade on each end.

Unplug and remove the voltage regulator on the right firewall.

On the regulator's connector coming from the wiring harness, look at the wires going into the bottom. Plug in a jumper to bridge the white wire and the yellow wire. It may appear that both wires are yellow (due to age). Luckily there are only two solid light-colored wires...these will be the white and yellow.

Plug the 2nd jumper between the black w/ white stripe, and the white w/ black stripe wire. Leave the other holes alone.

Reconnect the thick white w/ red stripe wire (Battery) to the similar point on the alternator.

Reconnect the thick black wire (ground) to the similar point (Earth) on the alternator.

IMPORTANT STEP: Go to Radio Shack and get a "1N5402" diode. This needs to be soldered inline with one of the wires on the plastic T connector that goes to the back of the alternator. If this step is missed, the engine won't turn off with the key!

Make sure the "line" on the end of the diode faces the connector. Don't solder directly to the connector like my graphic shows...just solder it inline with that wire of course. Diodes are sensitive to heat, so be careful not to overheat the leads when soldering.

COMMENTS: On startup I found my exhaust note is smoother at idle, and idle is rock solid. I suspect the more stable voltage at idle enhances the MSD ignition. On the road, the engine feels smoother with none of the hiccups I was getting when lugging the engine to low revs, or accelerating in too low a gear. Revving past redline is more smooth and solid with a bulletproof feel. My ammeter is solid and accurate, and my dash lights are brighter and wipers are faster. I measured 14.58 volts at the battery...just what it should be. I'm not saying this makes the car faster, but it's more driveable now without the voltage sagging at idle and redline like before. This is probably the easiest and most worthwhile of all the 240Z mods. I would save your old 240 alternator/regulator for an emergency, or to swap back to stock someday.

NOTE: You may need to come up with a way to shield the connector and jumpers from the elements. You could clip the connector from the old regulator to make a plug-in jumper arrangement which would look cleaner than just using two jumpers. I decided against that because a 240 regulator isn't as easy to find as it used to be, why hack it up?

 

AFTERMARKET IGNITIONS

Both Crane and MSD are battling it out on who has the best ignition. Both use the same concept: provide a multiple spark out to 3,000, and then change to a single hot spark. So the choice is up to you. I have used both a Crane Hi-6 and a MSD 6A on my carbureted F54, fired by a E12-80 on a ZX distributor, both felt similar to me. The Crane has a more advanced RISC processor, while the MSD has better credentials, your choice.

PERTRONIX

I haven't used one, but a friend has one on his '71, seems to work perfectly and I'm impressed at it's simplicity and quality. I would still pair it with a MSD ignition to boost the spark though...a great option if you can't locate a L28 electronic distributor. Make sure to lube up your breaker plate and check the operation of the vacuum advance dashpot.

CHEVY HEI MOD

Using a GM HEI module is a 20 year old way to put a 1975-78 280Z distributor on a 240. The problem is that the GM HEI was designed for the low redline of a V8 and is well-known for it's spark and poor saturation abilities above 4,500rpm, even Chevy people hate them.

I've heard of people pairing the HEI chip with their 280Z or ZX ignition which makes no sense: The E12-80 is a superior ignition module, adding an HEI is redundant. So while the HEI "works" for average driving, it's a cheap redneck mod and I don't recommend it. The HEI modules sold in the auto store sells for $14, the Nissan module for $200, you be the judge. Use the Pertronix if you want to save money.

PERFORMANCE

I spent some time on the interstate with a stopwatch doing 60-80 and 70-90 runs in the top three gears, comparing a E12-80 firing a MSD 6A, and a E12-80 module by itself. The times were within a tick of each other, back and forth. Kind of inconclusive. The MSD/Crane DO give smoother idle, need almost no choke, drive better when cold, and cut down on my exhaust smell at idle. But despite all these credentials, I'm not convinced they actually makes the car any faster. Sometimes I feel like the E12-80 alone actually has a little more torque. I've decided that on a carbureted motor, the better starting and idle quality alone are worth using a MSD-style ignition, even if I'm not sure the top end is better.

COIL TYPES

There are two basic coil types: oil-filled and 'solid' transformer style (like the Crane PS-91). But I wouldn't get hung up over which is better. The specs are what you should focus on.

A coil is simply a transformer that steps up 12 volts to several thousand. Its positive terminal gets a constant 12 volts to power it on, and a pulse to the negative terminal causes the windings to produce a large spark out of the center tower (this is the common setup on just about every car over the last 100 years). A capacitive discharge ignition like a Crane or MSD sends 450 volts to the coil (instead of 12). This is why a better ignition produces such a mammoth spark out of the coil.

Serious racing coils have very low resistance "primaries" (primary windings) which draw a large amount of current. This is why real racing coils are advertised to only run with a companion racing ignition: if you run them on a stock ignition they can draw too much current and damage things.

There are many performance coils out there, but some designs haven't kept pace with technology. Look in the Summit Racing catalog and you see several no-name oil-filled "performance" coils. I consider these worthless as they were designed for stock engines or muscle cars with points, not 10,000 rpm racing ignitions. I doubt they have changed internally since the 1970-'80s.

MSD and Crane make coils designed for high performance. I have used the MSD Blaster-2 (.73 ohms), Crane PS-91(.43) and PS-92 (.20).
I really like the Crane's E-coil design, and when I accidentally cranked the engine with the coil wire off, the end of the PS-92 was covered with crackling blue fire. This coil was HOT! The PS-92 mysteriously went dead after a few months though, I heard the same experience from someone else too. So I'm using a Blaster-2 again.

TACHOMETER

I would recommend getting rid of your old 240Z tach. Vintage, but not designed well, they're inaccurate and start jumping around as they age. They're not as accurate at redline as you would think, even when working well.I'm not into the white face look, I replaced mine with an Autometer #3990.

BALLAST RESISTORS

Surprisingly, stock coils on older 12V points systems on cars were designed to operate with a max of 6-8 volts.
The reason is that on points distributors the entire voltage from the coil passes through the points, and too much voltage can burn them out. So the ballast resistor was put inline with the 12+ wire to the coil to limit the voltage the coil puts out.

When you turn the key to start, the ballast is bypassed, and the coil gets a full 12V to put out a hotter spark for starting. Releasing the key inserts the resistor back into the circuit to preserve the life of the points. Why not design the ignition to use 12V all the time? Well, nowadays they do, but before 1977 or so that's the way points ignitions were designed.

This means if you buy a high performance coil and simply install it, the ballast resistor may limit the new coil's power output. On a points distributor If you connect a wire across the ballast, it will route a full 12-14v to the coil and pick up some voltage, but it can cause the points to burn out more quickly.

SPARK PLUGS

NKG plugs are the best I've used in a Z engine ~ smooth, predictable and long lasting. Bosch platinum are fine on German ignitions, but not on Z motors. I've been told that German ignitions evolved with a different overall resistance from coil to plug than Japanese ones. For whatever reason, many Z owners report misfiring and poor performance from Bosch. There's a big markup on "platinum" plugs too...companies know that people think products with "gold, platinum, silver" in the name are better. Centuries-old marketing...

I think the best Z plug to use is the NKG BPR6ES-11, all year engines. A few years ago Grassroot Motorsport magazine recommended the NGK ZFR6F-11 sparkplug for stock Z engines. It's a "V-Power" plug with a projected tip which extends out into the center of the chamber which simulates advancing the timing slightly by firing the mixture faster. Projected tips provide a more complete burn through the rev range, creating "free horsepower" and improving throttle response. Be careful using extended tip plugs in a shaved head or you might touch the piston!

Also, be careful about using multi-electrode plugs, especially on high compression motors. I spoke to a NGK tech once, who said that the nooks and crannies on multi plugs can create lots of little hotspots and contribute to pinging. Since a spark travels the path of least resistance, it's going to fire only on one of the multi electrodes anyway. He said that multis are designed for the modern hemi-style chambers on Hondas, etc.

My 2 CENTS: Don't waste your time on Splitfires or plugs that use hocus-pocus: use the plugs the factory chose. If you want to increase spark performance, concentrate on upgrading the ignition system instead. I use NGK BP7ES-11 plugs, which are one step colder than stock.

PLUG GAP TIP

Some people recommend when using a high performance ignition/coil to open the plug gap to .050 (or wider). This is said to create a larger, longer duration spark to increase power. But on high compression motors conventional wisdom is to keep it at .045, because as compression goes up, it's harder for the spark kernel to start. Crane says to use .045 for "offroad and high-performance usage", MSD says .050. NOTE: if you open it up to .050 on a stock ignition/coil you will only weaken the spark. I played around on mine and I like .045 with my MSD 6A, feels a bit "snappier" than .050.

PLUG WIRES

I really like 8mm Magnecor competition wires. Very high quality blue silicone, they are "real" competition wires and put the other designs I've seen to shame. Grassroots Motorsports Magazine did a test awhile back and found that these wires added 1.5hp to a stock BMW motor(!) But despite what people think, performance wires don't actually "increase" horsepower. They simply work transparently to allow the coil's full output to reach the plugs consistently. These certainly do, with very clean output all the way past redline, they even smoothed out my idle. Nice. Don't use the do-it-yourself Accel yellow performance wires. I've tried sets on different cars since 1980, and they tend to corrode inside.

 

MECHANICAL ADVANCE CURVE

This must be the biggest mystery in the Z world. I've been trying to get detailed info on what curve works properly for years, but the "authorities" seem to vanish when asked for details. According to Haynes manual, different Z distributors have different curves. But I've only seen only two different distributor choices on '81-83 L28s. If you take off the breaker plate, you can see "8.5" or "9" stamped into the top of the advance weights which I assume marks the total advance. "8.5" came on the manual transmission cars, "9" came on the automatic cars I've seen. The springs appear to be heavier on the 9. I've tried both and the 1981-83 "8.5" feels best on my 5-speed.

This is a 442.com page on engine power-tuning, applies to all engine but V8s are the reference.

BTW, if you want to disable the vacuum advance and run only mechanical, simply unplug the hose from the vacuum dashpot and plug the end going into the engine. The vacuum advance is completely disabled then, the mechanical still works.. Easy. Not running vacuum advance can make part throttle acceleration a bit sluggish, and supposedly hurts gas mileage. But vacuum advance doesn't work under full-throttle, so if you only drag-race vacuum advance isn't needed.

VACUUM ADVANCE

The dashpot that controls it is a big pain. It's purpose on the distributor is to react to vacuum from the intake manifold, and move the breaker plate with a little lever to keep the timing "optimum". It adds it's advance on top of the amount the mechanical produces.

The settings in the dashpots are different from auto to manual trans cars, and from year to year. So this makes it very tricky using ones from the junkyard, as you never know if you get one with the right range. However, you can tediously chip out the epoxy in the end to uncover a screw-within-a- screw, (these adjust the vacuum-arm range). I've played with a couple but never been able to get these settings to work properly.

Unfortunately, after 15+ years, most dashpots are leaking, causing no advance and a big vacuum leak into the intake manifold.

Test yours by sucking hard on the hose going into the dashpot. With the distributor cap off, watch the vacuum arm pull in. If you "hold" the pressure, the arm should stay fully retracted. If it slowly leaks down, it's internal diaphragm is leaking/bad...and it should be replaced (it can't be fixed). If it doesn't move at all the dashpot (or hose) is leaking a lot of air back into the intake.

If its bad, temporarily plug the dashpot hose going INTO the manifold, as it will have been leaking air into the engine. It's better to run without vacuum advance, than to lean out the motor and burn a valve. Unfortunately, disabling the dashpot can make the car diesel @#$%. You can still buy dashpots from the dealer.

DIELECTRIC GREASE [Dielectric (d-lktrk) noun.]

A nonconductor of electricity, especially a substance with electrical conductivity of less than a millionth (10-6) of a siemens.
Dielectric grease does not conduct electricity. It's purpose is to protect the surfaces of metal conductors from corrosion, sealing spark plug boots to keep water from getting in, as well as preventing arcing. Putting it on metal connections like distributor cap terminals, rotor tips, or injector contacts will block signal transfer. Personally I think the companies deliberately call it "Tune-up grease" so people will slather it on at tune-up time thinking it's some sort of metal cleaner.

To clean old connectors I like to use an exacto knife to scrape any oxidation off. Then use a quality contact cleaner/solvent to blast them clean. Standard brake cleaner spray is fine, but on electrical connections you want to leave a thin film of protectant on the metal to keep it from re-oxidizing. So when you're at the auto store try to find some electrical cleaner spray, CRC makes a good one. Places to clean are the voltage regulator plug, wiper motor plug, injection brain connector and injectors. Also open the injection airbox and spray the circuit board to clean the resistive wiper. Also check the little ground connector that screws into the lower shock tower to the right of battery on 240s.

MY OWN SETTINGS?
I use a 1981-83 manual-trans "8.5 degree" distributor, with the earlier E12-80 module on the side which fires my MSD 6A.
Yes the MSD is piggybacked on my E12-80...but the MSD is designed to be fired by an ignition module and is stable out past redline.
After lots of swaps and driving I believe this is the best setup for a L28 with flattop pistons. I like to advance the distributor timing about 4 degrees from stock.

 

EIGHTH - Cam

For years I tried to find a clear explanation of how cam duration operates. Finally in a generic hot-rod magazine I found the best definition:

"...as revs increase, the length of time the gas/air mixture has to make it past the intake valve gets shorter and shorter. At 7,000rpm, the valves are opening/closing 58 times a second, so there is almost no time at all for the mixture to enter. By making the duration longer, the valve stays open longer allowing more mixture to enter....creating more power."

This is why a short duration cam can't produce power at high revs, the valves aren't open long enough.

CAM RULES

BIGGER OR SMALLER? If you have trouble selecting between 2 grinds, choose the milder one.

DRIVABILITY: Choose the grind for the MAJORITY of your driving, not the occasional autocross.

LIFT: the max on stock Z-springs is .460, higher and the springs bind. Different tension ones must be used.

DURATION: Every 10 degree jump in duration raises the power band by 500 rpm. Don't use over 280 degrees unless the engine compression is above 10:1.

POWER: a hot cam adds 10-15% horsepower. Raising duration doesn't add more unless compression/ fuel/airflow are all increased too.

INJECTION: Since a hot cam changes the fuel and air flow of the motor, you may need to recalibrate the brain and airbox. Motorsport Auto can tell you which cams work for performance.

COMMENT: My feeling is that about 270 degrees (230@.050") of duration is right for street/autocross situations.

SINGLE PATTERN vs DUAL PATTERN

This is when the duration is the same between intake/exhaust lobes...or spread out (example: 260/260 vs 260/270).
The concept behind a dual profile is that if the exhaust valve has a larger duration than the intake, it will breathe better into a restrictive exhaust system and produce more torque. If you use a freeflow exhaust system the effect of a dual profile isn't considered as important. Performance turbo cams on the other hand can be just the opposite because of the different characteristics of the exhaust flow. As an example one turbo cam sold by MSA is 270/262 which is "backwards".

Deciding to use a dual or single pattern is not worth losing sleep over. I've used a two dual duration cams (Crane 262/272 and 272/282) with excellent torque and power. My current cam is a 268/268 duration (230/230@.050").

CAM BRANDS
Crane Cams used to make great performance Z cams. Not only did they perform well, but the lobe base-circle and cam dimensions were identical to the stock cam. At .450 lift they were simple drop-ins that could use stock lash pads and springs. All you needed were new rocker arms...perfect.

In 1996 I bought a 262/272 duration cam (#168-0010) directly from Crane for $118. But by 2003 they decided Z cams were "special grinds" and the prices went up to $300ea. Finally, in May 2005, Crane told me via email that they can no longer obtain the blank steel cam billets from Nissan, so they are dropping ZCAR cams from their catalog after many years of production.

All other cams on the market (Schneider, Comp Cams, Isky) are remachined (reground) from stock cams with smaller lobes that require thicker lash pads. Running thicker lash pads is OK, but they add extra weight to the valvetrain and are headache to measure and purchase. And after adding up the price of new retainers, lashpads, springs, labor and downtime, I think it's easier and cheaper to use a plain old drop-in cam.

CWC BILLETS

Stock factory Datsun cams are stamped "Japan" and are made of some very tough metal, lasting 200,000+ miles with no problems. But blank Datsun cam billet have been unavailable in the Nissan Motorsports catalog for over 5 years, and show as unavailable on the Courtesy Nissan site. So as far as I know no one makes new Zcar cam billets anymore except the company "CWC". So I looked up CWC on the internet and CWC Textron out of Michigan is listed as the "industry leader in ductile iron cams for passenger car and light truck applications".

Interestingly, my friend the Z Doc in VA. said he had noticed that aftermarket cams with a "CWC" marking were prone to lobe failure, especially when used with heavier springs. I took a look and both my failed Cranes were stamped "CWC", which seems to bear this out. I suspect that Crane really dropped their Datsun cam line due to too many complaints of cam failure. Since they seem to have been using CWC for years, their argument that they suddenly can't get the Nissan billets doesn't hold water.

THE SOLUTION:

Webcamshafts of Riverside, California caught my eye. They have 45 years experience with creating custom and antique engine grinds as well as a couple of decades of producing Zcar cams. And after talking to them on phone they appear to really know their stuff. It turns out they use CWC billets for their Z cams, but they "Nitride" them which involves heating them to 900 degrees and in an ammonia gas chamber. Nitriding creates a super hard lobe surface and is considered to increase the life of a cam 10-fold (no kidding). So I sent them my 262/272 (222/232@.050).450 lift Crane cam to spec out and use as pattern. They found that the Crane lift was more like .430 lift, and the base circles were of slightly varying height...so much for Crane quality control.

I resisted the temptation to go with their stage 2 cam the "# 91" which has 238/238@.050 duration which I felt would lose too much bottom end on the street. So after some discussion, I decided instead to order their "# 94a" grind which has .430 lift, 230/230@.050" duration which they said uses stock base circles(!) They list the 94a as 248 advertised duration which may look low, but it's the true 230 duration at @.050" duration that really matters.

So later when I opened my mailbox I found a nitrided, higher duration, new CWC billet cam with wonder of wonders...stock base lobe circles! I installed it in my P90 head in mid October 2005 I found the wipe patterns on the rocker arms were perfect...this makes the 94a a true drop-in cam! NOTE: If you go with their #91 or higher grinds I'm not sure if they can retain the stock base circles. Talk with them before you buy to verify what you want.

PERFORMANCE: Despite its moderate specs on paper, the 94a isn't a baby cam. The exhaust note is deeper than stock with a nice cam burble at idle which does best about 1000rpm. On the road the big L28 torque bump between 2-3K is lessened slightly, but it doesn't have that "dead below 3k" feeling of some higher duration cams. Acceleration is strong and linear down low and when you tach it out the acceleration is very strong and it pulls hard all the way to 6800rpm. It is a bit finicky in very cold temperatures, so you have to wait a couple of minutes for it to warm up.

VERDICT: The Webcamshafts 94a grind is an excellent all-around performance cam...the only one I know of using stock base-circles. It's great combination of driveability and performance. Recommended.

 

SPRINGS AND VALVE FLOAT

The redline on a 240Z is 7,000, the 280Z is 6,400. This has nothing to do with the springs however. The valve springs were identical from 1970-83 and a properly tuned 2.8 liter motor can easily produce power above 7,000. Redline differences on motors are because the larger an engine's displacement, the lower the useble power range. V8s can be a low 5,000 while a motorcycle might be 12,000 or higher.

Valve float is when the valve spring can't control the valve at high revs and the valve flutters on the seat. This makes the engine misfire and lose power of course. It became an issue years ago when American V8 engines came with poor valve springs from the factory and would float the valves at ridiculously low revs. So drag racers started installing heavy valve springs to try and control the valvetrain at high revs. But I've never heard of or experienced valve float on any Z motor with stock springs, they were that good from the factory. However, if you are rebuilding a cylinder head, I would replace your springs as it's a good time to do it.

ROCKER ARMS

You've heard this before, but when replacing the cam you should always replace the rocker arms. Everyone always wants to save a couple of bucks here, but you CAN'T. Even though the arms' surfaces might look smooth, they all have a subtle wear pattern that's mated to it's respective lobe. This mating takes place in the first few minutes of new cam/engine startup, and creates a perfect meshing between the two. If you use old arms with a new cam, the subtle wear pattern in the pad surface will wear into the cam lobes and damage them. This probably the most misunderstood part on a Z motor.

ROCKER ARM BRANDS:
I broke in a new cam a few years ago using the now discontinued Crane Cams rocker arms. Several months later the engine started missing. On investigating, several of my cam lobe tips were actually worn down(!) They were broken in properly and I always used quality oil, so this was a shocker. In looking at the rockers, the metal on the pad surfaces was porous and veined, and looked like cast pot metal. A Crane tech told me one the phone that the porous metal was "normal' and that it was a specially chosen composition to work with the cams. ...hmmmm. I only got 15,000 miles out of them. @#$%.

In comparing the other non-Nissan rocker arms, I noticed that the Sealed Power and Melling brand used the same cheap pad metal. Just speculating, but I suspect that Federal Mogul/Sealed Power wholesales their rocker arms to everyone, who repackage them under their own brand name. Beck Arnley sells them for $26ea which is about the same as Nissan, I suspect they may be the same part. The real Nissan brand rocker arms are unique, lighter, ultra-high quality forged rocker arms with shiny steel pads...the reason why Nissan cams can pass 200k miles with no problems. Expensive, but worth it.

Motorsport Auto sells real Nissan arms for much less than Nissan or Beck Arnley. I installed a set and they broke in perfectly. Please keep em' in stock Motorsport!!

I also just broke in a new cam with reground rocker arms from Delta Cams of Washington. They have two methods: you can order pot luck rockers from them or send in your own to be refinished. Personally I sent in my own to be refinished...that way I know their history and that they were all matched. They grind off as little as possible and for about $50 is a genuine deal.

 

NINTH - Lubrication

People get pretty passionate about oils. So if you don't agree with me, no problem. But here are my views on motor oil, which I stand behind.

HISTORY

The quality of the oils used in the 1970's-80's was horrible compared to today. The old oils sludged up, burned, and turned to varnish over time. I remember a mechanic telling me he knew when a car used Quaker State oil by the amount of gunk in the bottom of the oil pan. That's why the "in-thing" back then was to change your oil every 2,500 miles, otherwise it dirtied up the motor.

Well, motor oils in the past 20 years have come a LONG way, even more in the past 5, because of the demands of turbos and exotic high-revving motors. The secret of oil quality has to do with the API rating. The first letter (S) means the oil is rated for a gasoline engine. The higher the second letter, the higher the levels of detergent, varnish inhibitors, viscosity improvers in the oil. The old ratings from the 1970's (SA, SB, SC, SD) are obsolete, while today the current ratings are SM. That's why today an engine with 50,000 miles will be nearly clean inside, while motors from the '70s have a brown film baked on everything.

So changing your oil every couple of months isn't as critical as it used to be. The filter catches the dirt the same as it's always done, but the oil maintains it's slipperiness (viscosity) for well beyond 5,000+ miles now. The oil change Lube shops are having problems as a result. They still tell people to change oil every 3,000, while new cars manufacturers are saying 5-10,000. Times change...

SYNTHETIC vs. PETROLEUM - The age old debate

You'll get no argument from me: Synthetics are the best out there and help lengthen the life of the cam lobes. However there are a couple of rules you need to follow:

Don't use a synthetic in an old motor that's always used petroleum oil, especially if it's high mileage and been abused/badly maintained. This is because synthetic is highly-detergent, and can liquefy the old engine sludge and can clog the oil pickup screen. In any case, switching to synthetic on a motor with 180k miles isn't going to show much improvement.

Despite what Chevy and Porsche do, don't break in a motor with a synthetic. Rings and cam lobes need a certain amount of friction to break-in properly, especially on rebuilds. Break it in with a petroleum oil, and change to a synthetic at 1,500 miles.

Don't combine brands of synthetic. Some use different "bases", and may not mix properly.

SINGLE WEIGHT

A single weight oil (ex: 30W) remains the same viscosity in all temperatures, while multis (ex: 10W-30) change with temperature. Singles are identical in quality (SL/SM rated) to multi-weights, but people tend to overlook them in the store. They aren't good in low temperatures though because they thicken. Hence the creation of multi-viscosity oils.

Porsche used to recommend only single weight oils in their 911 engines into the 1970's, and Crane recommends only a "single-weight Pennsylvania crude" to break in their new cams. And engine lore, especially on motorcycles, is to use single weight to break in a motor. This creates constant friction at all temperatures for balanced break-in. I agree and use "Heavy Duty Castrol 30W" for break- in, until the rings seat at about 1000 miles, then switch back to a multi or synthetic. My friend the Z Doc recommends using a straight 30W in the summer in the southern U.S., and changing to a 10W-30 in the winter.

MULTI WEIGHT

Despite what your old manual says, don't use 10W-40. No new engine today uses it, and some manufacturers will actually void their warranty if they find you did. Instead, use 10W-30. Because it's lighter, it will free up a couple of horsepower and rev faster, and will reach all bearing surfaces more quickly. I wouldn't use 5W-30 or 0W-30, I think those are too thin for Z motors. At the same time, don't use 20W-50, that stuff is like molasses and is meant for older VW motors with large clearances.

OIL ADDITIVES

25 years ago when oils were crappy, using an additive was a pretty good idea. But today, SM grade oils are so superior they're not necessary. Have additive companies like STP even changed their formulation since 1980? I doubt it. The API rating is probably horrendous. But those companies keep cranking out cans of oil treatment like it's 1978 for some reason...I guess old men somewhere still buy the stuff.This STP FAQ sounds like it was written in 1963, notice there are no specs on the API rating.

MY CHOICES

Personally, I think Castrol 30w the best single weight, Castrol 10w-30 the best multi, Mobil1 10w-30 the best synthetic. Castrol Durablend gear oil is has worked fine for me in my rearend and gearbox. In my T5 I use Pennzoil synthetic ATF. Also like putting Marvel Mystery Oil in my gas occasionally to give the fuel pump a lube job.

OIL PUMPS

The 1981-83 Turbo 280ZX came with an oil pump that put out more pressure and volume than standard oil pumps. The automatic trans 280ZX turbo pump has a higher CC volume per rotation than the manual trans pump. The reason is that the auto trans cars came with an oil cooler and needed the extra "ummph" to supply to it. So upgrade your L series motor to a turbo pump and pick up better lubrication, and get your oil needle off zero. Mine hovers at about 10 psi and goes up to about 70. If you're lucky you can pick one up in the junkyard for next to nothing.

If you buy one new, be careful. The auto store might secretly list the same part # for stock and turbo pumps since they were physically interchangeable. I would buy a turbo pump from Victoria British or Motorsport Auto to guarantee you get a real one.

 

TENTH-Air Filters

I originally used the individual "mesh-flo" basket types for my SUs. They looked great and seemed perfect. Unfortunately the clips kept getting loose and I eventually lost them on the interstate.

After losing the clips, I installed a 240Z air cleaner and cut the old mesh-flo foam and stretched it across each carb inlet with a zip tie holding it to drive to the store. Strangely, I found the foam was restrictive, and the engine wouldn't rev over 3500rpm. It appears the foam in these "performance" filters is actually pretty marginal in it's flow capacity when stretched. It addition, they draw in the hot air from the exhaust manifold which isn't good for power. So here are my recommendations:

STOCK AIR CLEANER MODS

Use a K&N filter in the stock 240 air cleaner. This keeps all the PCV hoses and vacuum lines active, reduces intake noise and gas smell, and makes the engine bay look stock. ZTherapy says that the air horns on the 240 baseplate are actually better than aftermarket airhorns, and flow more than the carbs require so no anxiety is needed when using the stock housing.
My second choice would be the individual K&N filters that use nuts to hold the filters on, not clips. Keep in mind that open air filters bring in hot air from the engine compartment.

If you want to repaint your 240 air cleaner, use "Chevrolet Orange" engine enamel. Available from the auto parts store. I don't know what the original color was 30 years ago, but it looks factory to me.

COLD AIR INTAKE for CARBS

Here's a weird idea I came up with using a spare 240Z air cleaner. Seems to work well.

 

ELEVENTH- The Exhaust System

Since it's the easiest thing to upgrade, and sounds great, people always fixate on the exhaust.

HEADER vs STOCK MANIFOLD

The stock Z exhaust manifold is said to actually flow pretty well for street use. Quiet too.

A header is used to separate the exhaust runner pulses, and allows better top-end breathing by providing more "scavanging" of the gases from the exhaust ports. An interesting benefit is that gas mileage usually goes up. The standard improvement advertised by header companies on motors is advertised at 5-15hp.

While some people claim a header produces no effect, putting one on a motorcycle requires that you actually rejet (richen) your carburetors because it improves breathing so much. In addition, car legend is that the Corvette 427 L88 motor would pick up 150hp just by adding tuned headers. While I admit that a Z engine in stock form wouldn't benefit much from a header, I feel a L28 with a bigger cam, higher compression and ported head requires one. If you create a free-breathing motor that pulls 7,000rpm, putting a stock exhaust on it doesn't make sense. Every road-race car in the world uses headers ... good enough for me.

Headers are made of thin-gauge steel because they have to be bent into shape rather than cast like the stock manifold. The result is that they tend to rust through quickly. The solution is to get one with Jet-Hot coating. If you buy a non-coated header, before you put it on use paint stripper to remove the factory paint. Then prep and spray with a quality manifold heat paint. The paint they are shipped with usually flakes off...better to paint it properly before you put it on the first time.

I've only tried one header brand so far: Motorsport Auto 6-2. They sell a 6-1 and a 6-2 collector version. Supposedly one is better for torque, one for horsepower, I don't think it makes any difference. I like the 6-2 because fabricating the exhaust is easier...buy whichever feels comfortable to you.The welding inside the collector was pretty poor, and the fiber gasket they provide doesn't last very long. Still though, it's worked fine for me with no problems. I think Thunderbird, Monza and Pacesetter are the only other companies that still make them for Zcars. So if you find a mailorder company that has a "noname" header it'll be one of those.

If you plan on keeping your Z for another 20 years, I would make sure you have an extra stock exhaust manifold in the garage as a replacement. I suspect Z headers will be difficult to find in the coming years as the these cars get really old.

HEADER GASKET

I have the used the Motorsport Auto cardboard gasket several times on my header over the years. But it never sealed well and would break into pieces when ever I removed it, and steam cleaning the engine ruined it. So I tried a Fel-Pro stock gasket. It has a metallic core, and is covered in a soft metal foil for sealing. Despite the old wives tale that stock gaskets leak with headers, mine sealed tight as a drum. Maybe that's an old Chevy wives tale...

TIP: use a flat file across the ports on the header flange before installation to take off high spots. I believe this is actually where the leaks come from.

MUFFLER

Well, simply putting a loud muffler on the back of a stock system doesn't really doesn't do much more than make the car sound good. A quality exhaust consists of a free-flow header, larger diameter pipe, and quality muffler. Everybody gets hung up on the NASCAR parts like Flowmaster, or ancient Corvair mufflers, but those things don't fit well under a Z and I think they look dumb hanging down (sorry). My choice is Dynomax for a bullet muffler after the header to cut down on noise, and a Supertrapp 4" disc end muffler. The Supertrapp fits perfectly in the rear valance hole, looks mean as s**t, and is adjustable for sound and flow. Perfect.

PIPE SIZE

People have been arguing about whether to use a 2 1/4 or 2 1/2 " pipe for years. If you are doing competition then a 2 1/2" pipe will add more power on the top end, a 2 1/4" works and fits well for the street. Just don't lose sleep over which is best. Hate to break a myth, but I have used both and didn't really feel any difference. NOTE: if you have a catalytic converter, you can only 'legally' change the "cat-back" part of the system. Keep in mind that the Monza and Ansa brand systems are only 2" in diameter (boo). Also, the 240Z came stock with a teeny 2" exhaust pipe stock. Kudos if yours is still intact, but I would replace it with a larger diameter pipe.

HEADERS vs HEAD TYPE

All intake ports from 1969 to 1983 were round, the injection heads have a notch at the top for the injector. Use a carbureted year gasket to cover these if you want to use an injection head with carbs.

1970 through 1976 heads have square exhaust ports (E31, E88, N42)

1977-'83 heads use rounder, diamond shaped exhaust ports (N47, P79)

1981-'83 turbo heads have square exhaust ports (P90, P90a)

In terms of design, a retailer told me that all '77-83 headers are actually identical. The only difference is that '80-83 versions come with an EGR connection. So if you have a P79/P90 on a carb'd engine, just use a '77-78 header. I use a '77-78 Motorsport 6-2 with no problems. But don't start swapping stock manifolds back and forth. GET A HEADER!!

So you end up with a stock-looking 240Z with a ZX motor, superior electrical system and ignition, 5-speed, upgraded drivetrain AND a high-ratio rear end. A good old fashioned hot-rod using factory parts! Thank you Nissan for making all the parts interchangeable!