There are a lot of theories and even more opinons..So let's put it to the numbers..Which head is best for performance..?

The one with the most time and $$$ put into it! Really!!! Of course it depends on your definition of performance? Here is my qualified answer open for discussion, since I really haven't played around with all the different combos myself.

For a budget swap into a US naturally aspirated (N/A) 240Z or 260Z, my vote goes to the N42 because it is more widely available(lots of '75 - '76 280Z built), came ready for unleaded fuel with hardened valve seats and guides(which last way longer too!), fits the widest range of Z applications with square exhaust ports, and has the best compromise of compression and flow characteristics. Shave it a little and it is as good if not better than a E31.

Finding a good E31 can be like chasing a ghost and if you find a good one at a reasonable price you will still want to change the valves and the cam.

With the P series heads, unless you are swapping over the complete F54 block with the head or going with a Turbo or Supercharger the P79 & P90 series heads require to much developement(read $$$) to get good compression on a N/A L24, L26 or N42 block L28.

On paper the hot ticket would be stock F54 L28 N/A block (which had flat top pistons) and N42 head. Then add some cam work, some polishing and things would be getting really interesting.

Milage may vary! Making a fast car is just a function of time and money!

Who's next?

Goona haveto go wid da 42....but where's the 90a? It has a lot of fans.....

steve77

I'd get a P90A if it weren't for the hydraulic lifters that can't be replaced easily or without lots of money.

I read somewhere there's 2 versions of the E88 head also. I am interested in this because I wanna know which one is better as I'm looking to purchase a 240z which has the F54 block 280zx valves E88 Head, with cam and some porting etc....

The car goes like Hell and sounds like a mini V8 it has the twin exhaust pipes like the works rally car and it makes an unbelievable note...

I have a F54 Block and P90 head that I used to have on my 260z until it was smashed. Worked fine but the compression ratio wasn't good for a N/A car.

When I turbo it look out however.

By the way I believe that Tom Kaneiko I think that's his name with the orange 240z Turbo and nitros injection. It puts out about 500hp and he's running an E88 head.

Square ports rule.

Gav,

Almost forgot.

If I could find an E31 I would use that cause that's what they used for racing early in the seventies as it didn't have emission controls.

Gav,

This getting interesting. I'm currently running an N42, but am looking to change to a P90 w/flattops but I'm getting conflicting info on which will get me the higher compression..

The way I understand it is any of the first generation Z ('70-'78) heads combined with the F54 N/A block (which came with flattop pistons) will give you more compression (10+ if I remember correctly) then any second generation ('79-'83) head will with the same block. You can get high compression with the P90 series heads but you will have to do considerable milling and then shim the cam towers to get the cam geometry correct. From what I have heard it can work very well but it takes a lot of developement (time and $$$) to get it right.

That's what I have heard from the handful of people that have done it. Sorry, no first hand experience but it makes sense if you look at the specs of the different blocks and heads which are documented on several sites on the web.

The engine that Rebello built me 10 years ago is a N42 L28 block with stock stroke bored to 2900cc with 240 rods (which are longer than 280) and custom short dished pistons, to bring the compression ratio back to 93 octane street gas specs. Then they used my E88 head but upgraded the valve seats and guides to hardened steel and added 280 valves. I requested a street cam which I feel has limited the power curve to below 6k RPM. I installed it in my car with all other stock manifolds and carbs which probably isn't helping the power end of the scale either. So I probably don't have much more than stock HP but it has noticably more torque than a stock L24. I am considering upgrading the cam, exhaust, and ignition to realize it's full potential but my conservative setup is probably why it has lasted me so many years. From what I understand these days Rebello is building their current evolution of the long rod motor using F54 L28 blocks bored to 3.0l with stock stroke or 3.3l with diesel crank, 240 rods, custom short pistons with a modified (depending on budget) N42 head. They claim these motors are producing between 225 - 275HP with SU carbs and wouldn't doubt it.

I think that unless your head is wharped or otherwise damaged in some way you would probably be better off having it developed further than start over again. If you change from stock dished pistons to flattop pistons you will have a high compression hot rod motor for sure.

That's my opinion! I am open to hearing what other have to say on this topic because after 13 years of good service I am starting to plan my next motor. This one may not survive the abuse of my right foot much longer!

Have fun!

F54 block, balanced crank , rods and pistons, E88 head with 44mm intake 35 mm exhaust ss valves, ss valve seats, port polish, polished combustion chambers, 460 lift 270/280 duration cam. nismo tuned headers, twice piples just cuz i love the sound they make, triple 40 mm carbs, T5, 3.7 lsd

and let all hell break loose:o

hi,

what does shim the cam tower means?

Originally posted by Royce

The way I understand it is any of the first generation Z ('70-'78) heads combined with the F54 N/A block (which came with flattop pistons) will give you more compression (10+ if I remember correctly) then any second generation ('79-'83) head will with the same block. You can get high compression with the P90 series heads but you will have to do considerable milling and then shim the cam towers to get the cam geometry correct. From what I have heard it can work very well but it takes a lot of developement (time and $$$) to get it right.

That's what I have heard from the handful of people that have done it. Sorry, no first hand experience but it makes sense if you look at the specs of the different blocks and heads which are documented on several sites on the web.

The engine that Rebello built me 10 years ago is a N42 L28 block with stock stroke bored to 2900cc with 240 rods (which are longer than 280) and custom short dished pistons, to bring the compression ratio back to 93 octane street gas specs. Then they used my E88 head but upgraded the valve seats and guides to hardened steel and added 280 valves. I requested a street cam which I feel has limited the power curve to below 6k RPM. I installed it in my car with all other stock manifolds and carbs which probably isn't helping the power end of the scale either. So I probably don't have much more than stock HP but it has noticably more torque than a stock L24. I am considering upgrading the cam, exhaust, and ignition to realize it's full potential but my conservative setup is probably why it has lasted me so many years. From what I understand these days Rebello is building their current evolution of the long rod motor using F54 L28 blocks bored to 3.0l with stock stroke or 3.3l with diesel crank, 240 rods, custom short pistons with a modified (depending on budget) N42 head. They claim these motors are producing between 225 - 275HP with SU carbs and wouldn't doubt it.

I think that unless your head is wharped or otherwise damaged in some way you would probably be better off having it developed further than start over again. If you change from stock dished pistons to flattop pistons you will have a high compression hot rod motor for sure.

That's my opinion! I am open to hearing what other have to say on this topic because after 13 years of good service I am starting to plan my next motor. This one may not survive the abuse of my right foot much longer!

Have fun!

When the head is shaved (because it is warped, scratched, or for high performance tunning) the combustion chamber gets smaller which creates more compression. But it also changes how the cam timing relates to crank timing. If you shave the head enough, I don't know exactly when this is, you have to shim (by using shim type spacers) the cam towers (the metal castings that the cam bearings sit on) to get the cam/crank back in sync. You will also have to put different spacers, cannot remember the technical term, between the valve stems and rockers.

This is a pretty general answer to try to give you an idea what it means to shim the cam towers. Let me know if I didn't answer your question.

Hi,

sorry i still dont get it. too deep for me. the way i see it is we cut the head on the mating surface with the block, so to me the only thing affected is the thickness of the head. we did not touch the block nor the piston travel, nor the cam rotation (it still rotates at 360 degrees at the cam tunnel, so basically nothing was altered but the bowl on the head. sorry i am no mechanic i am just talking logically.

thanks,

hf

Originally posted by Royce

When the head is shaved (because it is warped, scratched, or for high performance tunning) the combustion chamber gets smaller which creates more compression. But it also changes how the cam timing relates to crank timing. If you shave the head enough, I don't know exactly when this is, you have to shim (by using shim type spacers) the cam towers (the metal castings that the cam bearings sit on) to get the cam/crank back in sync. You will also have to put different spacers, cannot remember the technical term, between the valve stems and rockers.

This is a pretty general answer to try to give you an idea what it means to shim the cam towers. Let me know if I didn't answer your question.

Can I throw a curve ball. The 240z I have came with a 05L head.:surprised It runs a garrett turbo charger and su carbie.I'm thinking it may have come off a L20. The combustn chamber is filled in but it only has the small 38mm valves and judging by the extra bolt holes around the manifold it may have been fuel injectd(haven't pulled the manifold off yet).I'm building a hot l24 with triples for historic racing and wonder is it worth spending the money on this head? Can anybody shed more light on the 05L?

Never even heard of an 05l head before???

I don't know which engine heads the L20 had but I'm pretty sure I recall something about a E30 engine head.

Seems a strange setup is it the L20 six cylinder?

If you going to go with an L24 setup I would change over to a early E88 or E31.

I've learnt the early E88 were almost identical to the E31's.

Also the earliest of the 240z's had about 9:1 compression and the L24 loved to be revved with the 3.9 rear end.

:classic:

Here in AUS anyway.