Maximum compression ratio

[GoMangoBoys]

I am doing a 360 / 408 build using the Trick Flow heads.  What is is the maximum compression ratio that I should consider for running on pump gas?
87 octane?
93 octane?

[jimynick]

Are you boring, too? Factory CR for my '74 360 was 8.5 and I believe about 9:4ish for my .030 over 408 kit. That'll be right on the ragged edge for 87 I would think, but cam specs can bleed compression, so you may get away with it. For me ( as I'm just getting mine in) it will be to see how it runs and if it pings or shows on the plugs, I'll go up accordingly. Good luck with it! 

[RUNCHARGER]

Yes: It's tied into camshaft as well. WAG and what I've used is 10.5 with aluminum and 9.5 with iron heads but I use 94 octane and I want to take no chances.

[Chryco Psycho]

It depends on Cam overlap , but also cylinder head design , combustion chamber shape can make a huge difference , swirl help a lot faster burn etc

[HP2]

Lots of dependencies in that calculation. As others point out above, there are a lot of factors that go into that figure, to include the altitude you will use the car at.

Generally speaking, a lot of testing, programs, professionals, data, etc, that I've seen, say that 180-200psi is about the maximum cylinder pressure that you can get away with using typical pump gas and premium cylinder heads. How much compression ratio is that, well, it depends on the above. So what do you do to figure that?

I've used this calculator in the past and found it to be pretty accurate. For boost, simply put in 0 if you aren't using forced induction.  This is for Harleys, but they are the same otto cycle as our engines. https://rbracing-rsr.com/comprAdvHD.htm

Got too much ratio, well, you can convert your fuel system to run E-85, or you can add a Methanol injection system using a MAP sensor to pull in the alcohol when pressure requires it.