Sheri, No I don't know what pistons are in it except that their Pontiac. My builder left town with no way to contact him. This is a 73 455, so he could have put in the lower compression pistons that came with the 73s. I believe he said the compression would be 9 to 1, but I can't remember.

For the balancer, yes it could be off, but if I advanced the timing to the point where the car wouldn’t start and then back it up slowly until it would start, then I'm assuming I'm close to the most advanced timing I should have. Yes? If I advance it anymore, it won't turn over well.

I haven’t tried a coolant tester, will do. My cap is old too, so I'll replace that.

The temp was about 70 degrees, the car was sitting in the garage with the garage doors open.

I checked out that post. There's miles of info on the affects of the radiator hose being higher than the radiator cap. I believe my hose is higher than the cap. I'll check when I get home (at work now).