Ok, not to sound stupid (SHUT UP LURKING ED!!!) but where would one get a
measuring device that measures in such small graduations of CC's??
HealeyRic2@aol.com wrote:
> Biff,
> Bob's right, the volume of your combustion chamber is the key ingredient
>here. On the 12G295 it's 28.3 cc. , compared to 24.5 cc on the standard
>bugeye head. You can get a rough estimate by levelling the head on a table
>with the combustion chambers upward, placing a piece of plexiglass with a
>small hole drilled in the middle over one of the combustion chambers and by
>using a pipette and a burette introduce a known quantity of fluid, like Marvel
>Mystery Oil, into the chamber through the hole in the plexi (you probably
>have some left over from your windblocker) If you start out with 28.3 cc of
>Mystery Oil and can't get it all into the combustion chamber, you know it's
>been skimmed. If you get less than 28.3 cc into the head, you can plug that
>amount into some formulas I have to figure out what your compression ration
>will be with the various mods done to your engine. Again, if you do hit 28.3
>cc, some other formulas will let you determine how much material needs to be !
> removed from the head to reach your target CR. Of course, depending on the
>cam you use and whether you have oversize valves in the head, excess skimming
>may cause your valves to hit your piston tops or top of the block (an
>expensive ouchey). I have a 12G295 head on my 948, bored forty over with
>flat-top pistons and am running the 88G229 Cooper 997 cam. The head has
>standard valves and I purchased it new. I never milled the head to boost the
>CR, but the engine produces plenty of power and runs fine on pump grade
>premium without any additives. You might want to go more wild with your motor
>so boosting your CR might be in the cards. Avoid going too high though,
>because using octane booster is a real PITA.
> Best regards,Rick
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