I would like to get some opinions on what would be the maximum compression ratio you could run an l20b at with an A87 head when running it on 98?

I currently have a compression ratio of about 10.5-1 with a u67 head and I have been offered an A87 head that has had similar work done so it would really just be increasing compression ratio.

You don't need it

In my experience....it really depends..... lol

What cam are you running? The dynamic compression ratio is very important. You can have the same static compression ratio with two different cams. One may ping it's head off and the other may need a higher compression ratio to work in it's optimum efficiency range.

What shape combustion chambers and pistons do you have ? Large squish areas between the head and pistons really seem to be key in L series engines. ie. an open combustion chamber head with the same compression ratio as a closed head will be more prone to pinging.

What fuel delivery system do you have ? EFI delivers a better atomized fuel / air mix and is less prone to detonation. I increased my compression ratio 1 unit after switching to efi.

What timing system do you have ? If you run a ECU then you can dial out timing around peak torque to avoid pinging.

But the basic answer to you question in my opinion is: I'm guessing the u67 is an open chamber design unless you have modified it. I would switch to the closed A87 head, if only just for the safety factor. Even if you still have dished pistons, the A87 head will offer better pinging immunity. I have run many L20B's on 98 with A87 heads and flat top pistons, but I did have to tweak the timing a little..... and never run anything lower than 98 or 100. I only use L series engines in my track car now, so buying fuel etc is never an issue.

Just my 2c!!
Jeff