swapping the evil 14092360 "peanut ports" on my 454 for some 215's. wondering how much more compression this will get me,assuming stock flat-tops. should i consider having them shaved a few thousandths before i put them on. going to add a COMP 274 XE when i do it,and want to be sure to give it enough comp.

Im assuming the block has not been decked? You can shave them about .012 (couple cc's less) and use a .020 steel gasket to gain a little more c/r. Here's how it looks. 98cc chamber (how you end up there is up to you and your machinist), .020 gasket (4.50 gasket bore), .025 deck, 4cc for the little dish in the piston, should get you about 9.2/1. Not bad! Those heads are pretty good, I have a set in the shop right now getting worked over.

Back From the Dead,
You are probably already aware, but thought I would post this. I have the 215 heads on my 396. I was going to install an XE274 Comp cam. But the springs they suggest and sell would require machining of my 215 heads for their springs to fit. I went with another vendor and their springs, Lunati.
If you are going with other springs then not a big deal. Just wanted to pass this along in case you were thinking what I was.

ya, comp recomends the 924-16's. but i,m just going to check the lobe lift on the cam in the engine the heads are coming off of. i'm pretty sure that they will be good, because it was set up for a pretty hairy cam form the way it sounded.

We did this awhile back to vintage 1973 454 shortblock with the stock flat tops.Bolted on my old 215's and using a .039 headgasket,worse case scenario is 8.9 to 1

ya, i'm hoping for 9-9.5:1 to make the 274 cam happy.