Ryan77

When i build my new motor, I'd like to run the highest compression ratio possible, while still using 93 octane pump gas. I'll be using aluminum heads. So what is the highest I can go :confused:

Les

Tough question to answer because it really depends upon cylinder pressure & therefore depends upon what cam you'll be using. Ballpark ratio would be 10-10.5 to 1 if you want to be able to throw as much timing at it as you choose- you could probably run higher ratio if you don't mind limiting timing a bit but I think that's defeating the purpose. Post your cam specs if you can. If you can't get a good answer here(I'm pretty sure some of the boys can help you out though) I'd check w/ cam maker & head maker to pin it down. Good luck. :cheers:

1979toy

Your dynamic compression ratio will be the determing factor in what octane fuel you can use. Keep in mind that fuel gets put in the wrong tanks at the gas station from time to time and you may not be getting the preimum that you're paying for.
You can find information and a program to figure your dynamic compression ratio here; http://cochise.uia.net/pkelley2/DynamicCR.html
Good luck with it.

Ryan77

I now planning on building a 388 since it's much less $$ than a big block. I'll basically be using the dyno tested 383 package on the AFR website, except more compression and 5 more cubic inches. The heads are the AFR 190's with the "competition package", and the cam is the Comp Cams XR288 roller, with .520/.540 lift, advertised duration of 288/294, and a duration @.050 of 236/242. Thanks for the response so far :cheers:

Ryan77

10.5:1 and 36* of timing with the setup I posted above, will it work on 93 octane?