hey whats up guys...
i have been researching about 84.5mm blocks matching to 81mm heads, i know many ppl leave the head at 81mm and run their cars fine, but there are other ppl who say that the sharp edge from the 3.5mm difference might leave hot spots that lead to detnotation...
so now if you were to bore the head to match the block to 84.5mm then you lose compression..
ok so this is the question...

my overall compression goal would be a 9:1 compression... but how much would losing some compression from boring out the head to match the 84.5mm block affect the overall compression???
which pistons do i order?

9:1 CP pistons or 9.8:1 CP pistons or ???

this would be for a b18c1

thanks for your input and help

charlie

 

Order the high compression pistons since it will lower your CR from that. If you start with a 9:1 then open the chambers up you will be below 9:1 then. I run an 84mm bore with a stock B16A head, no problems at all like my ported head I had before that was bored out and too much unshrouding for the valves which led to blown headgaskets. The valves were overly UNSHROUDED!

 

thanks for your help...so your setup is a 84mm block with the 81mm b16 head?.. im thinking about not boring out the head and jus keeping it but.. i dont want any detnotation problems