Vikki. One thing you need to consider for both of your motors is 0-deck. Please take a look at this from Cliff Ruggles.
would zero deck the block vs milling the heads. There are other side benefits from this procedure. Having the block decked/squared will insure that the distance from each head to crankshaft centerline is the same. Although Pontiac blocks are usually much closer in this regard than other brands, few are perfect. For medium compression engines built to use pump fuel it becomes much more important to maintain the quench distance of .035-.040". The engine will also run cooler zero decked. Without exception, every Pontiac engine I've had in here that had running hot/overheating problems had the pistons .020" to .030" in the holes.
The following is a recent example: We just finished a well prepared 400 engine for a 66 GTO. The owner is a very competant mechanic by trade, he owns several older high performance vehicles. Last year he completely rebuilt his 400 engine with catastrophic results. A set of #62 heads were used with stock replacement cast pistons, Summit 214/224 cam, Torquer I intake and Edelbrock 750 carb. The engine ran so hot he could not drive it. It also detonated under all circumstances, after an entire summer of tuning without improvement, he removed the engine and brought it here. We made a few minor changes.
The #62 heads were mildly ported, combustion chambers polished to a mirror finish and the exhaust crossover filled with aluminum. The cast pistons were the 8 valve relief replacements and were .030" in the holes, they were replaced with TRW forgings and the block was zero decked, a set of .039" head gaskets were used. A larger 221/229 cam was installed with HS high ratio rockers. The Torquer intake was replaced with an RPM. An 800cfm q-jet and HEI distributor were prepared for the new engine. The new engine manages pump fuel without problems despite being slightly over 10 to 1, compared to the previous configuration being closer to 9.5 to 1. It never gives the first indication of wanting to go past 190 degrees even on extended cruises at freeway speeds. The previous set-up would continue to heat up on extended cruises eventually reaching over 220 degrees where it had to be shut down to cool off.
I know that some of you suspect that it is the TOTAL package that changed the results. About 5 years ago I had a nearly identical 400 engine in here with the same history. I DID NOT rebuild the engine, but spent countless hours trying to tune it to get rid of the detonation/overheating. This included a new (expensive) radiator, waterpump/pulleys, several types of fans, etc. When I finally threw in the towel and pulled the engine, you guessed it, the TRW forgings were .032" in the holes. The engine was zero decked, slight cam change and no problems thereafter.......Cliff
