The main issue with this engine build, as I would eventually understand it, is that he used flat top pistons on a stock deck height block. The problem is that the pistons are .085" in the hole (below deck) at TDC and therefore can not take advantage of quench (getting the top of the piston to within .040" of the head surface, which creates turbulence (good burn) and allows the use of pump gas in a high compression engine.


The other issue is the cam. It's a good low end torque grind, but the spec calls for a minimum of 9.5:1 compression. I gathered all the info regarding combustion chamber volume on different heads, 906/516/452, and ran them through the compression ratio calculator. The 906 heads that were on the motor have 79cc heads, which will get me in the ballpark, but they were in need of a complete rebuild which would cost $600-$700 locally. This was above the price range of new cast iron Aeroheads which are rebuilt castings, but with the bigger valves. So, might as well do that huh? Well, the price on those heads had since gone up and to get them to me would be close to $1000! About the same price as 440 Source aluminum Stealth heads.