so i have a P90 head and a N42 head what do you guys recomend me using on a L24 block? while still using my su carbs

Both of those heads, without being shaved, will lower the the compression ratio on a stock L24. Although I'm not an expert by any means, those heads would probably create valve to bore clearance issues (without bore notching), as well. Others, more knowlegeable, will chime in and correct any of this info that is inaccurate.

I wouldn't recommend either of those heads. If you're looking for performance on a stock L24 block, and if you have access to other heads, I would recommend an E31, early E88 (smallest combustion chambers of the E88 series heads), or Maxima N47 for a stock L24. The Maxima head should yield the highest compression ratio of the three. Best wishes.

sweet thanks alot!

The best kind of head, that would be the kind you get from your girlfriend for free. jk

Do a search for a utility called lengine to do the math for you. Very handy. Or go here. I can;t speak to the valve clearance, but the N42 would put your compression just a tad higher than an E88, and a few points lower than an E31. You can also go here for more info:

http://www.ozdat.com/ozdatonline/enginedesign/

Enigma,

You are correct regarding the later, and larger chambered versions of the E88 vs. the N42. Please note that I said early E88 head. The first of the E88 series heads had combustion chambers that were essentially the same size as the E31 combustion chambers. Therefore yielding higher compression on an L24 than would an N42 head.

Roger that Roger. Thanks for making the distinction I failed to consider.