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Old 11-09-2012, 08:16 PM
69 widetrack 69 widetrack is offline
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Originally Posted by cobalt327 View Post
The 6X-4 heads have a smaller chamber. Makes upping the CR easier.

Using the -8 heads you need to remove a little over 0.050" from the head decks to get about 8.5:1. These are rough estimates- the heads have to be CC'd to know what the volume actually is. I have never tried to get 9:1 using -8s, so someone else can fill you in on the plausibility of that. My thoughts are it will take too much milling, but that's me.

The '75(?) and newer 400 pistons have a large chamfer around the outer edge, plus a dish and valve reliefs. Your earlier engine doesn't have these pos slugs, so that's a plus as long as they weren't replaced w/the later pistons or those godforsaken 8 valve relief "one size fits all" pistons.

Use straight wall studs (ARP p/n 190-4003 w/hex nuts, or p/n 190-4203 w/12-point nuts, or stock BBC studs will work) to get away from the weaker bottle neck studs.

Some Pontiac info:

Pontiac engine info
See, there you go, lots of good information this site.
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