NG horsepower upgrades

[Hoffman Anthony J A1C 552 CMS/MXMVC]

>>>my cam will be my 272, I will not be using equal length headers, and as
for cr of 12:1, sounds a bit high for my liking for reliability, what is
everyones opinion on a >>>sensible cr? 


First, the dynamic compresion ratio varies with the cam. In other words, at
low speeds, because of the overlap of a larget cam, the cylinder doesn't
fill as completely. This efectively lowers the CR at low RPM's, which will
reduce the tendency to preignite. There are several other factors, the
biggest of which is the size of the piston. The larger it is, the better the
heat dissipation is. On a VW 1.8 with 3.40 pistons 10:1 is about the limit
for the street on 91 octane. My 351 Ford has 4.030 pistons, and it runs
10.5:1, no knock sensor, no pinging ever even on 85 octane (huge cam,
though). 

Just some info the chew on,
Tony Hoffman