assimilated420

yeah lower compression w/o a turbo and plus with the exhaust manifold being round ported and the block square.. it would fit... but youre only hurting yourself at that point... stick with what ya got and maybe look into a new cam.. also i would mke the exhaust as free flowing as possible and youd put some numbers in..

juggalo280ZX

I will be getting a stage2 cam along with the 3.1 bore kit, therefore I would no longer have dished pistons, then would I recieve a benefit? Either head needs to be machined for the bore kit anyways, so I'm not worried about having to do that.

assimilated420

you still run into the problem with the exhaust manifold.. the p90 has square and the manifold has round... it will not flow well and cause leaks and other problems.. stick with what ya got.. it will work just fine

flightforlife07

OK I think I already asked this question but how low can your compression get before you can't run teh car... I have a 1980 block with an n47 that when I get the head machined will have somewhere around 10.19:1 psi. I also have another 1980 block that I think has dished pistions along with a head from a 1981 that blew up the head is still good its a p79 and when I put that on the block the compression will only be around 7.51:1 psi is this bad or should I just try to find another n47 and use that?

lww

Sorry about that. It's back up now.

jfairladyz

juggalo280zx, it's really not worth changing out your head man. Get the cam, and if you get a good port job, and polish those exhaust ports you'll have a very potent head.

lww

It can go really low before it won't 'run'. However, it'll make less power. So running at idle is one thing. Having the power to pull a 2900lb car away from a stop sign is another thing altogether.

If you're planning to do a turbo later, then I would do the P79. It's a better chamber design than the N47 and you'll have a decent but somewhat lower starting compression for making boost later.

You will have less torque and ultimately less hp until you add boost.

flightforlife07

if I do go with the p79 and add the turbo later does that mean that I eventually have to upgrade to the turbo injectors and ecu and everything else turbo to make it work right?
Thanks

juggalo280ZX

I believe so, but the others guys know a lot more than I do, I'm just typing what I believe is what I have read on here before.
I would personally keep it NA. after the money that you spend "Turboing a Non-Turbo" as Bleach has put it before, you could've done a whole head rebuild, or if you got some machining conections, a 3.1 Big Bore Kit. Plus...no turbo lag!

jfairladyz

No and No. But you will have to upgrade to something along the lines of engine control and injectors. I'm not saying it can't but I don't think it's a good idea to run the stock NA ecu on a turbo'd car. As far as injectors go, you don't want to over tax your stock injectors either, so you should atleast upgrade to the turbo inj. You don't neccesarily need anything off the turbo engine, but you do want to upgrade your fuel system to keep up with the extra air from the turbo or you'll have trouble. A rising rate FPR is a cheap alternative to an engine management systems.

Oh and as far as turbo lag goes, as long as you get a snail with a turbine and compressor that is matched to your particular application, and don't go extreme, you wont even have turbo lag. A properly sized turbo rolling on ball bearings will spool up before you can even get the pedal all the way to the floor. So don't worry about that.

lww

A 0.3L isn't going to make up the difference of a 2.8L turbo and an NA 3.1.

For the price of the 3.1 you can do a pretty awsome custom 2.8 turbo...

jfairladyz

3.1 turbo. Yeah baby. Wouldn't expect it to last forever though, running those cylinder walls that thin and running boost. CRACK! Overbored RB26DETT's can't even stand up to high boost pressures, those things crack between the #'s3&4 cylinders all the time, even without the overbore.

Bleach

hehe... ya, thats what I'm talkin about!

lww

It's mostly about block selection. My 3.1 Turbo had 12 blocks sonic tested before one was deemed suitable for the build.

I know Dave Rebello builds 3.2L strokers and he goes through the same selection process. His motors aren't running boost, so he has less to worry about with wall thickness.

Anyway, unless your motor is being built by an L series expert, and I'm not talking about the guy down the street, stay away from the big bore. There are only 3 people in the country that I would trust to build a stroker motor and 2 of them are in the SF Bay Area. Sunbelt Performance in GA, Rebello in Walnut Creek CA and Rob Fuller at Z Car Garage in San Jose CA formerly of Scott Performance.

It only takes one little mistake in the build process to send you on a search for another motor... And when you're talking about boost on top of that, you better have the best guy money can buy or you'll be spending all your money on replacement motors.

You either pay up front or you pay on the back end. Believe me, it always cost less to get it done right the first time no matter how expensive it feels at the time.

jfairladyz

lww, how much overbore was called for on the 3.1?

flightforlife07

Has anyone ever heard of a, Os Giken Tg24-B1 head? I was wondering wut it is and if its possible to use if I can find one

jfairladyz

If you mean the TC24-B1, then yes I've heard of it. Mucho dinero. And that's if you can find one. I've tried several times to get in contact with OS Giken and their US distributor with no luck at all. The only one thats ever been known to have made it's way to our shores(on a rally Z) made it's trip back to Japan along time ago. But yeah, if you can find one it'll fit right on there. But you have to use all the OS G. related parts that go along with the head. You cant reuse any of the parts off the L-series heads. Last I heard, it was going for $10,000, and that was quite a few years ago.

I wish you luck, and if you can find a way to get ahold of one, let us know.

Bleach

You'll never find one of those heads. NEVER!

jfairladyz

That's my opinion. God knows I've been searching for two years now, and I haven't so much as heard where one MIGHT be, for sale or not(in any country). It's like trying to find the Virgin Mary's face on your pancakes, ain't gonna happen.

For that money I could just swap in an RB, and according to Hybrid Z, the engine just bolts right to the existing mounts. Need to fab a tranny mount though.

flightforlife07

Ok I know this post must be aggravating everyone but I got a few more questions about it......

I called a dismantler to find out if they had a N47 head from a 1980 280zx..... So a few weeks go by and I called back today to see what was going on with it and they said they have it. I can come down to make sure its the right one anytime...

Does anyone have any suggestions on what to look for to make sure it isn't cracked and what not... Its used of course so it's probably dirty... but any thoughts might help.

Then I asked what it was going to run, he said he needed to check prices but around $250 everyone can imagine what I was thinking at that point... so I was wondering if that was a good price for a used head that I still have to take down and get rebuilt when I buy it.

I wish I had never over heated the car in the first place
Thanks

jfairladyz

Check for cracks between cylinders, around water jackets, and inside the combustion chambers. Pay close attention to the areas around the valves. This can all be fixed with welding, but that's expensive and welding and aluminum head is not something the novice wants to do. Bring a known good straight edge. Not a ruler, an actual straigt-edge. Check and make sure the head is completely flat. Check it diagonal, lengthwise, etc... It's expensive to straighten a warped head. They can't just mill it, they have to use a heating process to straighten it. If it is milled(very minimal warpage) you'll have to use a thicker head gasket to keep compression within reason. And the heating process doesn't always work.

jfairladyz

Oh, and as long as you can inspect the head before you buy it to make sure it's rebuildable, then that is a good price, especially if it's a full service yard(sounds like it to me). I was quoted just a little less than that for a head but that was from a do it yourself pick and pull.

flightforlife07

what about an e31 from a 240 will that fit and would I have any problems if I put it on my l28 with flat top pistons

jfairladyz

NO e31 on l28 with flat top pistons. You're compression would be way too high for a street car. If you're building a race car with the appropriate fuel, then the head is more feasible with the compression you'll end up having. If you had dished pistons, you'd end up with amore ideal compresion ratio. The e31 had a very small CC, something like 42.5 cc.

flightforlife07

I used the L-6 engine builder and put the e31 with all the specs I have and it said the conpression would be around 10.61:1 I heard somewhere that you can run up to 11:1 on regular pump gas... HTe reason I asked was because there is an E31 on ebay and I was just wondering since the only other option I have at this point is a used N47 for $250 plus another $250 to get it rebuilt. THe E31 is already rebuilt so... Thanks