What is the standard on the most compression

I'm going to do a 380ish inch 12:1 pump gas engine next year (I hope). Carb'd. It shouldn't be an issue.

Compression ratio and pump gas is combo dependent. I'm already running 11.08:1 on pump gas and I really should pull the heads and slip the thin head gaskets in there and make it 11.25:1 because...well, because there is no reason not to really.

You ain't going to do something like this buy off the shelf cams, and not understanding what the proper combustion chamber shape should look like.

If you get those two things ironed out, 12:1 isn't unreasonable and 11:1 should be the standard.

I forget to mention you need to be able to read a spark plug and making tuning decisions from that.

If you do that, you can do more CR than most. Most guys are scared and believe what they read in magazines and on line.

An aluminum head will NOT take more CR than iron. It's just not true. Whatever you do with aluminum you can do with iron.