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Re: More HP!
9.5:1 is considered the practical limit for 93 octane and iron heads. We (CVMS) always "dish" the piston for more volume. The heads must first be measured ("CC" the chambers). Between the chamber and dish, total volume should be no less than 84 CCs. That does NOT include the "dead area" (head gasket). A 3 1/2" dish, .080" deep usually "does the trick".
It can also depend on which piston is used. Are they true "flat tops"? That would mean 4 valve releifs. Or are there 8? Some replacement pistons have both the 12 and 19 degree valve reliefs in them to enable use of early heads or later heads. The 16s are "later" (12 degree).
Cam selection can also have a significant affect on fuel requirements. A "smaller" cam (short duration) can increase cylinder pressure at lower engine speeds, creating a situation where detonation can occur. A longer duration cam can "bleed off" SOME of the cylinder pressure at lower engine speed, but does nothing for it at higher speeds. We've found the Comp XE series to be the most effective at making power in lower compression (under 9.8:1) engines.
I wrote "Chapter 2: Building Your Shortblock" and "Dishing and Detonation" in Jim's book. I can help a lot if you let me. Many of those recipes are mine.
When choosing a compression ratio, it's better to "err" on the side of caution. That is, the little gain from 9.3:1 to 9.8:1 (about 2%) is NOT worth the hassle of proper fuel and tuning for the higher ratio. "Pressing the edge" is only good for "class racers", where every inch-ounce of power is called for. 5 HP won't make a difference in a street or bracket car.
Good luck with the Poncho. And welcome to the higher side of GM performance!
Jim
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