All things being equal, I'd be willing to bet the 8:1 engine with 7psi will make more power than the 9:1 engine at 5psi.

Crutching the blower with more compression works great with a 177. Simply because 7psi isn't an option. Well, you could overdrive it engough to make 7psi, but its past the blowers efficiency , and a waste of time . so 9:1 and 5lbs works best. the 250 will be OK at 7psi, but that's about as hard as I'd push it. I wouldn't run 7psi with 9:1 and the 250. I've done it, but its not what I'd recommend to a buddy.

Thanks for the info Joe!

Regarding the heads, they're already done in terms of porting, etc. I need to change out the springs and retainers (originally setup for a HUGE solid roller... sad that the titanium retainers have to go) and switch to Inconel valves. I guess I could have them shaved since they're coming apart anyway, but that wasn't really in the game plan. Not much work though.

That sheds a lot of light on things, Joe. Almost like a light bulb going off!

Yes. 5 psi should be good for 34% more power, 7psi for 47%. The 1 point of compression is generally worth 4%. So maybe 9% more power with the low compression high boost scenario?

I have a set of standard pistons marked 14097021 if they will help you out. They are stock out of a 454 mag and still have the rods attached.

I hate dipping into this stuff so late at nite but i swore the merc bbc blower builds had quite a dish in the piston to hit that 7.5 with off the shelf heads .could almost do a good shot of whiskey out of one . If it was clean .

That is correct. Here is a pic of one[ATTACH=CONFIG]539079[/ATTACH] But on second thought, this is a pic of a 502 blower piston, not a 454.

I believe the 525sc has a very similar piston to that one cannot remember the chamber volume but they were also set to 7.5 to 1