How to lower compression on a 3.6
 

What are the options for lowering compression on a 3.6 964 motor? (to get it down to about 9:1 compression)



Shave pistons? Spacers under cylinders? ??

Kirk

Kirk:

Don't use spacers as that adversely effects deck height. Increasing deck height increases the propensity for detonation by leaving more end-gas at the perimeter of the chamber near TDC.

Machine the piston domes but you'll not get it to 9:1 without seriously compromising piston strength,..............

I've heard of many people machining the domes of the 964 pistons down to 8.5:1 for forced induction application without any dramas, even for up to 1.2bar of boost.

I believe Henry of Supertec has done this many times with great success, as does Protomotive. The 964 piston crowns are very thick. You can't do it with 993 pistons though.

Thanx guys.
Im trying to figure out all the options for installing a supercharger I picked up. Its quite the learning curve!

Kirk