Upgrading L24 head for L28 block....

[san_maru_zed]

I have got an L28 block in my 260z with the standard dished pistons. However the head is the smaller(40cc) E88 closed chamber with L24 valves (pretty sure it has 42mm intake vales, vs 44mm for the L28). The engine is otherwise a standard L28 with EFI.

The engine is rebuilt and has only done about 100km. She goes pretty well, and I've always had it on the cards to put the L28 sized valves in, just wondering though if ,from people's experience, weather it is really worth it and if they noticed a difference?

Ray

[jmortensen]

I think it is worth it. Here is a good related thread with nice pics of what should be done to the chamber, although this head still has the smaller seats in it: http://www.classiczcars.com/forums/showthread.php?t=13114&page=1&pp=15&highlight=E88

If you haven't already seen it, it is possible to get a P90 which has a better combustion chamber shape and shave it .080" to get compression. Then you shim the cam towers up .080 to restore the cam geometry, and use the longer N42 or N47 valves in it. If you're looking for a head to use with pump gas, that's the way to go IMHO. The machine work is quite a bit less expensive than installing new seats in the E31 head. There's a guy with all the info on his site, I think it's called the Datsun Garage, but I can't find the link right now. If I had it to do over again I would have sold my E31 to someone who wanted the original head and done the P90 instead...

[san_maru_zed]

Thanks for the link.

Actually my head is the same combustion shape as the P90. Before I put my head on the block I had my mates P90 beside it, exactly the same chamber design except his obviously had a larger CC.

Looks like it might be worthwhile changing those valves afterall.

Ray

EDIT: Maybe I've confused some ppl. The head is a Skyline E88 head which is the same as your Maxima P79(or is that N47?) head except the E88 has square exhaust ports.

[jmortensen]

Wow, I wasn't even aware that head existed. Sounds like a good one to start with.

[NZeder]

I have been told that a good head to use is the 260c (Cedric) E88 head (sound like the one you have already) these have the smaller valves (like yours) and a very good shape and the smaller cc. You just install the L28 valve etc and your in business.

I am only going by what I have been told so this is second hand and I have never seen a 260c E88 to compare to my 240z and 260z E88's that I have.

[san_maru_zed]

Yeah, could be the same one. Was just interested in weather or not 2mm of intake valve would make that much difference.

I have been told that a good head to use is the 260c (Cedric) E88 head (sound like the one you have already) these have the smaller valves (like yours) and a very good shape and the smaller cc. You just install the L28 valve etc and your in business.