Blue Thunder, while I'm sure it can be done, I'm not sure if it's a good idea to recommend 9.5 and iron heads and a blower without providing a lot of detail. I wouldn't attenpt that without an intercooler, good 93 octane perhaps with a splash of race gas, no thermostat to keep the head temps down, timing, fuel mixture, etc. When the 525SC came from Merc. it had 7.5 compression.

Change to an intercooled set up. Measure how far your pistons move down in the bore from TDC to determine your stroke. It may be a stroked 454 which will be i think a 489 when only bored over .030"

I agree patriyacht and in fact do run alum heads. I didn't do the calc on his compression but thought someone said it was 9:1 which would give an equivilant result (detonation wise) to mine with 9.5:1 and alum heads. That is if the quench is set tight and the ring end gaps loose along with the proper setup of the other items you mentioned. I don't use an intercooler.

It Isn't Stroked at all. Already measured cause I was told it was a 496.

I did all the measuring for the compression ratio. Heads were 101cc. Piston dish was -8.5cc. Piston was .025 below deck at TDC. Head gasket 4.375" x .035 thick. Cylinder diameter 4.280. Stroke 4.00" Ratio = 8.71 to 1

Ok, dish pistons. Then it was just bad tuning or bad gas. Looks like your block was never decked. Thats lucky. Toss that odd head and get a pair of more recent heads with 119cc chambers and a set of flat top pistons.