The factory ratings were: Compression Ratio 10.25:1 HP 360 @ 5000 TQ 475 @ 3200 From what I have learned though, these numbers were a bit optimistic. Larry
I CC'd a 69 430 some years back and it came up to 10.0 I rebuilt a 76 455 a few years ago. I decked the block .030, used 69 model 430 heads and the compression was only 8.8 when the book said that it was 8.5 from the factory. It was more like 7.5.
I still have my 69 430, it just needs pistons, one is cracked in the skirt. I got this motor with 125,00 miles on it and stuck it in a 75 Monte Carlo (had no skylark at the time) It ran better than the 455 and went 8.20's in the 1/8 mile. That was a fun car.