flightforlife07

Hi, I was just wondering if the head from the 1981 280zx and the 1980 were the same. I took my head to get rebuilt and they told me they couldn't because it was cracked. I have the head from my 81 that threw a rod so I was just wondering it was possible to just just that head for my 1980. are they the same and do they bolt up the same? Thanks.

Heat Rave R

As far as I've heard, all L-series heads are interchangeable.

WildmaN

Yeah heatrave's right. When I had my head redone on my '81. I ended up having a Turbo head from a '82 or '83. And it worked fine. There wasn't much choice considering the wrecking yard only had one or 2 Z's at the time. And my head would have cost more to fix than get another used one to rebuild.

PBGreg21

Be careful when you get a new head tho, make sure you get the same number (N47, P79, P90) or you could screw up your compression.

DoTheDrew888

You may have compression ratio issues if you swap heads. I believe the '80 was an N47 head and the '81 is a P79 head. If you put the P79 on a block with dished pistons than you will have considerably lower compression. I think lww said it would be about 7.3:1 compression. Not the best for an N/A engine but perfect for a turbo setup.

wayneinky

Head on 1980 should be N47 and have round exhaust ports. Head on 1981 Non turbo should be P79 and have round exhaust ports as well. 1981 TURBO head should be P90 and have square exhaust ports. The P90 head should bolt on, but the issue would be which exhaust manifold you use. I don't think the round 1980 exhaust manifold will bolt onto the 81 Turbo P90 head.

Wayne in KY

Bleach

The compression is the main problem. So the answer is NO you can not just swap on any Z-car head you want onto any block.

1981-83 you can interchange heads. If you have a P90 on your turbo, you only want to use a P90 or P90a

If you have a P79, you only want to put on another P79 or a P90/P90a.

If you have an N47 head, only use an N42, N47 for best results. The 240Z heads will fit your 75-80 Z but they have smaller valves for the smaller 2.4L engine.

As was said, in any case, check the exhaust port configuration. Use the manifold that matches your head. Do not intermix a manifold made for round ports on a head with square exhaust ports. All intake ports are round so that is not an issue.

flightforlife07

ok... I already had the block rebuilt and I have flat top pistons and now I don't know if I can or can't use the head from an 81. I already have the head and just need a clear answer. thanks for your help

DoTheDrew888

You can use the P79 with the flattop pistons, or you could put on the N47 but it will raise your compression considerably. The '81 head should be a P79 so you will be fine.

lww

You can use this tool to figure out what will keep you in the safe compression range:

http://www.kamikazeracing.net/dl/L6-enginebuilder.exe

Good luck.
lww

s/cL3.0

I think that is the best tool I have seen next to the tranny ratio site..

flightforlife07

I'm still working on getting a new head due to the cracks in mine, but I was wondering if I port and polish my head and my manifold will it mess with the emissions or would it be ok to do, or should I not even bother. Thanks

DoTheDrew888

Which manifold are you taking about? The exhaust manifold I hope. You do not want to port and polish the intake manifold, it if rough for a reason.

flightforlife07

Yea the exhaust manifold sorry. I was just wondering if it was ok to port and polish the head and the manifold.

DoTheDrew888

Yes that is fine, Port and polish on the head is a very common way to make some more power. I've heard of poeple porting the exhaust manifold also. Another option to porting the exhaust manifold would be to buys some headers though. It would be a more effective way of getting better flow.

flightforlife07

hey guys thanks for everything about the heads the link is down does anyone know where else to get the engine builder because I wanted to try another configuration I downloaded it but I always just ran it instead of saving it (stupid on my part) if nayone knows where to get it let me know...oh and I was wondering if u can use the p90 without a turbo I know its a turbo engine but do u have to have the turbo on it or will it run without it?

Thanks

DoTheDrew888

You can use the P90 without a turbo, a lot of race engines have that setup becuase the P90 flows so well.

flightforlife07

if I don't use the turbo do I still need to get the turbo ecu and the high flow injectors and everything else to run the turbo or will everything from an na work

DoTheDrew888

Everything from an N/A will work. It is basically like having a ported and polished head because it will flow better. One thing you have to remember though is that the P90 has square exhaust ports. Your exhaust manifold ports may not match up perfectly to the head ports but it will still work.

jfairladyz

As long as you have the NA distributor and AFM, you're good on the electrical side with the NA ECU.

Bleach

Only the exhaust runners are slightly larger. The valves are all the same. The intake port runners are all the same as the P79. Don't expect a ton of horsepower gains if you're going from a P79 to a P90. Plenty of race engines were built using P79 heads with the steel exhaust liners still in place. But the P90 is said to be the best Datsun L6 head made. (even if it only has minor advantages)

juggalo280ZX

Would I be able to bolt the P90 onto my 1980 ZX? that was my original plan but after this thread, I have become skeptical and want to double check.

assimilated420

you can.. but you dont want to.. not unless you get a turbo manifold and yeah well thats a whole other process.. stick with what ya got for now..

juggalo280ZX

Why would the manifold be a whole other process? this winter would be when I do it, if I do it.

DoTheDrew888

If you did that you would have really low compression because the N47 has dished pistons and the P90 has a large chamber. It would be a very crappy setup without a turbo. If you turboed the motor also then it would be basically the same as a normal turbo motor, with some minor differences.