I bet if you put the numbers down correctly it would only be 9.5:1 with the 53cc heads. My 1983 305 was about 10.2:1 from the factory. Flat top pistons with 6cc worth of valve reliefs, .025" down...

That is interesting....I have run 1.94/1.60s on a .030" over 305 which is a 3.765" bore and it had plenty of clearance. 059 heads BTW. At .600" lift it had more than .100" valve to bore clearance. ...

They have a very similar chamber to the 14022601 truck 305 HO heads. I had a 1983 G20 Van tha had thise heads. It ran very well with those 53cc heads. The 059s and 520s have a very abreviated...

I am a little off on the lift of the HO cam. The specs I have are for the roller version used in the 87+ LB9/L98/9C1 engines.

https://m.summitracing.com/parts/mel-ccs-37
...

I have run the Stock 305 HO grind in several TBI and TPI setups. Has a smooth idle with plenty of vacuum and makes good mid-top range TQ and HP.

Its like 202/207@ .050, .415/.430" lift cut on a...