Hi redline loss or gain
03-21-2002 | 03:48 AM
#1
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Hi redline loss or gain
I am doing the L28 swap and using my E31 head with SU's or my DGV webs. I would like to know if I will be sacrificing my hi redline of the 240 since I am using the L28 block, or if I will still have the hi redline because I am using the E31. If that is how it works. I know the L24 was a revier motor is that because the crank, rods and pistons, or the head and cam combo.
What turns? There all straight to my Z
What turns? There all straight to my Z
03-21-2002 | 11:16 PM
#4
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Re: Hi redline loss or gain
aha, I see said the blind man. Thanks for the info. I'm dieing to make the swap I just need some time where I won't need my car hopefully this weekend, so I can go terrorize some more Honda's. If anyone has anymore usfull info please let me know.
What turns? There all straight to my Z
What turns? There all straight to my Z
03-22-2002 | 10:40 AM
#6
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Re: Hi redline loss or gain
7000 grand?!?!? 7,000,000?!?!?! dang thats fast how do I get my Z engine to do that??? hehe sorry I couldn't resist
-Steve
http://www.geocities.com/stev240z
-Steve
http://www.geocities.com/stev240z
03-22-2002 | 10:45 AM
#7
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Re: Hi redline loss or gain
YEAH it is the small stroke that will allow higher revs, but really that's only because it's easier to balance the smaller stroke.If you balance your L28's bottom end correctly you can make it handle 10,000 RPM. HOWEVER, you will need the appropriate bearings, oil pump, water pump, belts, alternator, AC pump that will handle that high of RPM.
OK I'm getting off subject, all your Z crap should handle 7,000 rpm and if your L28 block isn't entirely out of balance, and the block is ALL you're changing (not the head, cam, or springs) then you should be OK.
Just as important as the balancing of the bottom end is the valve springs.
OK im getting off track again... bottom line... valves don't float, bottom end doesnt have excessive vibration from lack of balance, and you camshaft is setup to put out power at the RPM, you're ok.. if you want more details I can go off for ya...
-Steve
http://www.geocities.com/stev240z
OK I'm getting off subject, all your Z crap should handle 7,000 rpm and if your L28 block isn't entirely out of balance, and the block is ALL you're changing (not the head, cam, or springs) then you should be OK.
Just as important as the balancing of the bottom end is the valve springs.
OK im getting off track again... bottom line... valves don't float, bottom end doesnt have excessive vibration from lack of balance, and you camshaft is setup to put out power at the RPM, you're ok.. if you want more details I can go off for ya...
-Steve
http://www.geocities.com/stev240z
03-25-2002 | 03:22 AM
#9
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Re: Hi redline loss or gain
Hey stev240z, go off hit me with your best shot no pun intended. I wan t to know cause I will either drop it in as is or get a little wild. since it is out of the car and I don't need it, I just want it.
What turns? There all straight to my Z
What turns? There all straight to my Z
03-25-2002 | 03:39 AM
#10
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Re: Hi redline loss or gain
since i got the stock L26 camshaft in mine.. it doesn't really like going past 6000... no power really past 5500
<font color=blue>76 260z</font color=blue>
The NiteRider
<font color=blue>76 260z</font color=blue>
The NiteRider
03-25-2002 | 04:09 AM
#11
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Re: Hi redline loss or gain
Your block is an L28 with a L26 cam. I just don't want to lose all my top end. Granted I love all the extra torque I'll get. But I want at least 6500 out it. Maybe I'll pull the crank and have it balanced. Would 280 pistons fit on 240 rods, I could just swap the crank and rods. My old 260 would pull allthe way to 7200 and still have power, I would only do that in3rd so 4th didn't seem so week.
What turns? There all straight to my Z
What turns? There all straight to my Z
03-25-2002 | 10:56 AM
#12
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Re: Hi redline loss or gain
OK, Sam, some of this may be a little redundant..
It is the camshaft that decides when and how much fuel enters the engine, the other engine components just have to live up to the camshaft's expectations. The fuel injectors need to be able to spit out enough fuel, the throtte body needs to be able to allow enough air in so it doesn't run rich, or of course if you're running a carb (or carbs) it (they) need to be able to provide with what the engine is suckin'.
Just like the intake system, the engine system needs to be able to withstand with what the camshaft wants. If the camshaft is setup to peak at 4,100 rpm (like in my Cherokee 4.0), then the valve springs should be able to now allow valve float to at least 5,000 rpm. If the camshaft is setup to peak at 8,000 rpm, the the valve springs need to be stiff enough to not float until at least like 8,600 rpm.
Once the valves start to float, there's no power,simple as that. I've noticed, when missing a gear (that's a whole other story cuz it's an automatic), that my Cherokee (which redlines at 5,000) engine hit almost 6,000 rpm and didn't float any valves, but there's NO WAY it was still putting out power worth a damn. I did notice, however, that the engine was shakin like a *****, because its a decently long stroke and it not balanced to be revving that high.
SO one would think, OK my valves aren't going to float, so I'll get the power, so I'm gonna put in a cam that tops at 5,500 rpm and shift at 6,000 rpm (remember, we're talking about my Jeep engine here, and I'm using it as an example because of it's long stroke) which would theoretically WORK, but your components on the bottom end of the engine are destined to fail, because they are not setup for that extra 1,000 rpm you want. The bottom end will shake, even if it's not noticable, and render the components connected to the crankshaft useless.
This summer, I'm rebuildng the Jeep engine and expect the shift points to be around 5,800 rpm. It's going to be bored and stroked, balanced and "cam'd". NEW stock valve springs will be used because they are rated to "float" at 6,500 rpm.
Now how does this relate to the "Z"? Why does everyoe say that the longer crank doesn't allow for higher RPM? I'll tell you.
Obviously the z engine is made to rev way higher then my Jeep engine, the L24's tach's redline is at 7,000 rpm, while the L28's tach's redline is at 6,500 rpm. I've never driven a car powered by an L24, but have driven on a few L28s. The power is lost pretty much at 5,200 rpm an most will shift at 6,000 rpm. When I was 16, I would shift at 6,500 - 6,7000 rpm because it wasn't floating valves, this was before I found out what it can do to the bottom end!
But why did th L24 come with the higher redline? Is it easier to rev higher quicker? Yes. The shorter stroke produces less friction when the piston is moving and less movement on the bottom end, so yeah, it's easier. Nothing that can't be made up with on an L28 with a longer stroke by using a lighter flywheel.
MY understanding is, if you take a L24 built up to it's max, with the camshaft and valvetrain setup for 8,000 rpm, you're still going to need a balancing job done to the bottom end. If you take that same valvetrain and head (not factoring in the compression ratio difference which is compensated anyways by the dished pistons), and put it on the L28 that has been just as balanced as the L24, you will have more power (more cubes)an an engine that is capable of revving just as high. How FAST it gets there I don't know. I would think the added power would more then make up for the additional friction caused by the longer stroke, no?
With the Z engine, as opposed to my Jeep engine, Building it to rev high like a ***** would be cause for worry (like 8,000 rpm)about the alternator, a/c pump, oil pump, water pump, and pulleys. Are they able to withstand being driven that fast? Is your belt going to turn inside out and fly off? Adding another 800 - 1,000 rpm to the shift points on my Jeep is realy nothing to worry about because it's a serpentine belt and its still under 6,000 rpm.
Personally I think an L28 that tops at 5,500 with a turbo and a decent cam is the best way to go when keeping the original engine. That's my plan for the '78. The '71 is a completely different story (no smog inspections for it in CA), and it's getting an LS1 someday.... but in the meantime it's got twin SUs (on an L28), and a header... cam is coming on soon... and I don't consider high revving a problem at all... I usually don't take it above 6,000 rpm anyways (I think, the tach doesnt work yet).
-Steve
http://www.geocities.com/stev240z
It is the camshaft that decides when and how much fuel enters the engine, the other engine components just have to live up to the camshaft's expectations. The fuel injectors need to be able to spit out enough fuel, the throtte body needs to be able to allow enough air in so it doesn't run rich, or of course if you're running a carb (or carbs) it (they) need to be able to provide with what the engine is suckin'.
Just like the intake system, the engine system needs to be able to withstand with what the camshaft wants. If the camshaft is setup to peak at 4,100 rpm (like in my Cherokee 4.0), then the valve springs should be able to now allow valve float to at least 5,000 rpm. If the camshaft is setup to peak at 8,000 rpm, the the valve springs need to be stiff enough to not float until at least like 8,600 rpm.
Once the valves start to float, there's no power,simple as that. I've noticed, when missing a gear (that's a whole other story cuz it's an automatic), that my Cherokee (which redlines at 5,000) engine hit almost 6,000 rpm and didn't float any valves, but there's NO WAY it was still putting out power worth a damn. I did notice, however, that the engine was shakin like a *****, because its a decently long stroke and it not balanced to be revving that high.
SO one would think, OK my valves aren't going to float, so I'll get the power, so I'm gonna put in a cam that tops at 5,500 rpm and shift at 6,000 rpm (remember, we're talking about my Jeep engine here, and I'm using it as an example because of it's long stroke) which would theoretically WORK, but your components on the bottom end of the engine are destined to fail, because they are not setup for that extra 1,000 rpm you want. The bottom end will shake, even if it's not noticable, and render the components connected to the crankshaft useless.
This summer, I'm rebuildng the Jeep engine and expect the shift points to be around 5,800 rpm. It's going to be bored and stroked, balanced and "cam'd". NEW stock valve springs will be used because they are rated to "float" at 6,500 rpm.
Now how does this relate to the "Z"? Why does everyoe say that the longer crank doesn't allow for higher RPM? I'll tell you.
Obviously the z engine is made to rev way higher then my Jeep engine, the L24's tach's redline is at 7,000 rpm, while the L28's tach's redline is at 6,500 rpm. I've never driven a car powered by an L24, but have driven on a few L28s. The power is lost pretty much at 5,200 rpm an most will shift at 6,000 rpm. When I was 16, I would shift at 6,500 - 6,7000 rpm because it wasn't floating valves, this was before I found out what it can do to the bottom end!
But why did th L24 come with the higher redline? Is it easier to rev higher quicker? Yes. The shorter stroke produces less friction when the piston is moving and less movement on the bottom end, so yeah, it's easier. Nothing that can't be made up with on an L28 with a longer stroke by using a lighter flywheel.
MY understanding is, if you take a L24 built up to it's max, with the camshaft and valvetrain setup for 8,000 rpm, you're still going to need a balancing job done to the bottom end. If you take that same valvetrain and head (not factoring in the compression ratio difference which is compensated anyways by the dished pistons), and put it on the L28 that has been just as balanced as the L24, you will have more power (more cubes)an an engine that is capable of revving just as high. How FAST it gets there I don't know. I would think the added power would more then make up for the additional friction caused by the longer stroke, no?
With the Z engine, as opposed to my Jeep engine, Building it to rev high like a ***** would be cause for worry (like 8,000 rpm)about the alternator, a/c pump, oil pump, water pump, and pulleys. Are they able to withstand being driven that fast? Is your belt going to turn inside out and fly off? Adding another 800 - 1,000 rpm to the shift points on my Jeep is realy nothing to worry about because it's a serpentine belt and its still under 6,000 rpm.
Personally I think an L28 that tops at 5,500 with a turbo and a decent cam is the best way to go when keeping the original engine. That's my plan for the '78. The '71 is a completely different story (no smog inspections for it in CA), and it's getting an LS1 someday.... but in the meantime it's got twin SUs (on an L28), and a header... cam is coming on soon... and I don't consider high revving a problem at all... I usually don't take it above 6,000 rpm anyways (I think, the tach doesnt work yet).
-Steve
http://www.geocities.com/stev240z
03-25-2002 | 10:07 PM
#14
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Re: Hi redline loss or gain
Well, having the ability to rev past 6,000 has it's advantages, you rev it higher then when you shift youre at a higher power output rpm range. Doesn't really put much power out after 6,000 though, does an L24? I'd like to know actually, I'm under the impression their cam setup is about the same. Does an L24 just zoom up after 6,000?
-Steve
http://www.geocities.com/stev240z
-Steve
http://www.geocities.com/stev240z
03-27-2002 | 12:03 AM
#16
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Re: Hi redline loss or gain
On my roomates L28 77' 280Z everytime he lets it go past 6000 we have to do his valves he doesn't even have power after around 5300. Mine will freely run 8-9000rpm with no float. Has no pull past 6600rpm. So its not even worth going there.
What turns? There all straight to my Z
What turns? There all straight to my Z
03-28-2002 | 07:59 PM
#18
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Re: Hi redline loss or gain
Wow, these are exciting posts
All things being = a short stroke engine will out rev the long stroke, because the limiting factor is piston speed. You can't exceed a cetrain piston speed (5000 fpm as I recall)
However most engines cease to produce power becuse of airflow. An engine is just a pump. at low rpm the air doesn't fill the cyl properly, so power is down. As the engine revs build -- at some rpm, the cyls will be completely filled and the power will spike. I see some newer ECU's take advantage of this and spike the spark advance and fuel.
At the high end of rpm it becomes more and more difficult to move enough air thru the head -- so power begins to fall off
Most speed mods seek to move the power band toward the high end -- sacrificing low end.
Old Hot rod axiom - only cubic inches and compression ratio raise power across the rpm range -- everything else is power curve reshaping
All things being = a short stroke engine will out rev the long stroke, because the limiting factor is piston speed. You can't exceed a cetrain piston speed (5000 fpm as I recall)
However most engines cease to produce power becuse of airflow. An engine is just a pump. at low rpm the air doesn't fill the cyl properly, so power is down. As the engine revs build -- at some rpm, the cyls will be completely filled and the power will spike. I see some newer ECU's take advantage of this and spike the spark advance and fuel.
At the high end of rpm it becomes more and more difficult to move enough air thru the head -- so power begins to fall off
Most speed mods seek to move the power band toward the high end -- sacrificing low end.
Old Hot rod axiom - only cubic inches and compression ratio raise power across the rpm range -- everything else is power curve reshaping
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