Hey,

I was wondering something about cylinder heads, now I'm doing a complete engine build up and it's time for cylinder head selection. My question is, is there an advantage over 72cc or 64cc (Sportsman II heads)........I know 76cc will drop compression on a stock rebuild but this is a whole engine project so I will select my pistons according to my cylinder heads. So if I can keep the same compression with either (9.75:1) is there any avantage over one or the other?

 

I've always heard that the combustion flame propogation works best with a flat top piston, as compared to a dished or domed piston. Since you are selecting pistons and heads at this time I would suggest calculating your compression ratios based on using a flattop piston and see which head chamber volume brings you closest to your CR goal.

 

You will probably find that with flat top pistons, 58-64cc will give you the right compresion. Also,the smaller chambers promote a faster burn. The large chambers were primarily designed to allow for larger valves, but there are more benefits to having the smaller chamber with the flat top pistons. Plus, larger valves have been put into 58 and 64 cc heads. I'm not sure how big you can go, but I'm sure someone else knows.

------------------
89 Transam GTA, 350TPI, auto, 3.27 rear, dual cats, gray.
Magnaflow cat-back,
K&N open element,
Best E.T. 14.63@95mph