Hot Rods compression guess on chevy 396

I’ve got a pair of #206 396 heads going on a’89 454 . With steel head gaskets I should be in the 9 to 1 cr. range.


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Don’t have to look it up, I had a 4778 DP in 1970, about the time they were released, although they might have first come out in late ‘69. The DP series started with the R-4776-AAS @ 600 CFM, the 4777 @ 650, 4778 @ 700, 4779 @ 750 and lastly the 4780 @ 800.

 

4.094" is stock bore, so it's likely that it's standard size.

What clues tell you it's a 375 hp engine? The stamped code? 4 bolt mains? Doesn't have rectangular port heads, so that's not one.

 

Those are forged pistons.....

 

Did the 4 bolt 396 have Hi Perf cast in it on the side?

 

I don't remember. My 2 bolt block has PASS cast on the top rear, I think.

 

I had a buddy who had what he told me was a 396 block, it was bare, but had “hi Perf” cast in it(pretty sure that’s what it said). Just was curious

 

there are various things cast in various places...I think many blocks say "HI PERF" "PASS" in at least one place. but I think it has to do with which blocks use that particular mold...so the ends of the block will say several things, even though the block itself is only one of those things. Hard to explain....but what it means is, don't get too excited about a block just because it says "HI PERF" somewhere on it.

 

It's a 2 bolt block. Whatever it checks out to be, I have a couple sets of heads to cover my build. I really thank you guys for all the help>

 

My FM books shows 2240 as a 396 325/350 closed chamber.

 

Also my 1966 SS 396 350 said HI Perf 2 bolt main engine

 

You should also smooth out those notches in the block that gm did to unshroud the valves ...Take your head gasket and scribe around the inside of the gasket so you get something like this View attachment 5627723