Hey guys, I have a 94 5.8 roller motor that I am going to rebuild. My dilemma is that I am going to use a set of Roush world products heads and I would like to run flat top pistons but if I do that it will bump the compression up to 11.1? or somewhere close which will cause me to run high octane gas! Which I want to avoid! Can someone tell me if I am correct or maybe tell me what the comp ratio would be with flat top pistons and these heads? I beleive the stock comp ratio is 8.8.1? The specs for the heads are: 200cc intake runners
64cc comb chambers 2.02 intake and 1.60 exhaust valves.

thanks!

 

I should have asked if anyone knows the specs for the stock 94 5.8 heads as well?? As well as the stock cam specs for the same motor? Anyone??

thanks

 

Go to www.kb-silvolite.com they have a compression calculator. They also sell dished pistons to lower the compression if needed. Or, you can call them. They are nice folks to deal with.

 

64cc heads are pretty much the most you'll find for compression ratios, they go down to 58cc as well. I have 64cc heads, .60 compressed head gaskets, and with probe forged pistons it comes out to around 9.5:1. You just need to get the correct piston and head gasket so that if used on a 64cc head, will net you the compression ratio you'd like to have. The place you buy the parts from or the manufacturer should be able to provide you with the info.

 

Thanks for the advice!

 

Thanks for the advice!