Edelbrock heads

Whats a KM? hahahahahahahaha

Original poster, determine your needs, the fuel you will use, the cars use and your wants, then post them here and Ill try and give a honest answer. I can build a 9-1 engine that will rattle itself to death so compression isnt the determining factor.

Actually, car manufacturers all over the world are building engines with more compression than ever before. They are using the "crutch" of cam timing to allow it. You are basing your opinion based upon your failures, others of us base our assertions on our successes.

There were plenty of people who called the gasoline internal combustion engine, a "fool's errand."

... problem is the OPs question asked for max compression on pump gas with Edelbrock heads, so those who responded conservatively were assuming conservative street build. Others considered more the limits of what can be done with pump gas. This is what leads to comments ranging from 9:1 to over 12:1 as possibilities.

The dynamic compression ratio calculation is just a tool. It helps, but isn't conclusive in saying an engine will or will not ping, e.g. my engine has a lower DCR with the 250@0.050" cam and aluminum heads than it had with the 224@0.050" cam and iron heads, but tends to ping a bit more with the bigger cam depending on the tune and the loading.

If we could somehow add the sensors, electronic controls, direct injection, variable cam timing, bore size, combustion chamber & piston design, etc. of today's engines, then we could run today's compression on lower octane gas with mild combos without concern ... but would be simpler, cost less, have lower emissions and burn less fuel to simply fit a modern engine.

Uncljohn's response is reasonable for a mild build. Nothing wrong with being conservative if that's what you're after.   

Tony's response was best ... asking for more specifics of the OPs plans to give a better suggestion as to what will work for his application.

Thanks,RD.