cholds

Built a 455 with the 2323f pistons, when all said and done, they are sitting down in the hole .056
I have had some heads milled down to 69ccs years ago. They would give me good compression but is the quench with a .040 gasket too big allowing detonation or does it matter with open chamber heads. .096 is a lot what can I do.. Also with 18cc dish does it matter that the outside on the pistons are zero decked. Its not much of a rim thats zero. Thanks

83hurstguy

Not much you can do. Deck the block, run thinner head gaskets, or change the pistons.

I would probably just run it, quench is not typically an issue on an Olds engine from anybody I've heard. There are probably people all over doing it, and have no idea what they actually have in the engine.

67OAI

You may experience detonation with .096 quench; you could try a thinner head gasket (I would get the thinnest available). Generally a minimum of .045 total quench is recommended when using steel rods to prevent piston contact with the cylinder head.

74sprint

I'm kind of confused here, are you saying that the dish is 0.056 down the cylinder and the outer rim (flat) is 0.000 down the cylinder? If so then you have 0.000 quench and the block must have been zero decked. This part of the piston (outer rim) will hit your head. Also if this is the case then the only quench you have is the thickness of the head gasket. With these pistons, 0.040 gasket and 69cc heads you should end up @ 10:1 compression, good for high octane (91-93) pump gas on the street. Note: the more quench you have, the less compression you have, and the less likely you will get detonation. Quench is usually measured at the spot where the piston comes closest to the head but, you can have a quench area dislocated from the quench spot eg. hemi dome pistons.


Ray

cholds

Ok let me try to confuse you more.. The pistons are .056 below deck. The pistons also have a 18cc dish. I was wondering if bringing the piston up to 0 deck, then its just the outer rim of the piston thats at 0 not the whole piston as its dished. If you have seen the 2323 piston, Im not sure how much is 0 as it has a small ring around the outside of piston thats taller than the rest of it because of the dish. Kind of like a 1976 factory piston where you can almost eat cereal out of them. If its detonation one worries about, wouldnt we worry about the dish in the piston as its also empty space below deck. The squish from a flat top at 0 is ideal compared to a dished piston. Dish has more space between the deck and top center of piston. Was kind of wondering if its important to have that 0 deck for squish quench whatever you want to call it to prevent detonation at 10.5:1 with the dished pistons. My dished are .056 in the hole plus the dish.. where as a flat top is flat across the whole cylinder. I think chevys are matching from piston to head in a closed chamber fashion. Does it matter with olds since they are open chamber about quench or is it ok to make compression however you want .. ok confused you more. but Im sure some will know what Im getting at. I just dont want to be pinging down the road. I think the late models get away from it because compression is way down so maybe not as important for a 0 deck.

cholds

Im saying the piston, the outer rim, before dish is .056 down.

cutlassefi

With 9.5:1 or so you'll be fine, run it.
I personally know of a builder that does marine twin turbo 1400hp 557 BBC's that run on 93 pump. The pistons are .100 in the hole and they run just fine. You'd be surprised how little squish some exceptional engines really have.

cholds

I getting 9.95:1 if I use a thin head gasket. 10.85:1 if its 0 decked and .040 gasket. Is it worth it? or can you deck a block that much and stay in the geometry.. Im using Edelbrock Aluminum heads.

Bore: (diameter)
4.155

Stroke:
4.250

Cylinder Head Volume:
69

Effective Dome Volume:
Use (-) for Dome and (+) for Dish.
+18

Deck Clearance:
.056

Compressed Gasket Thickness:
.027

Number of Cylinders:
Compression Ratio : 9.95 : 1
Total Displacement (in.3) : 461.01
Total Displacement cc's : 7557.54

cutlassefi

Use a .017 shim gasket then.

74sprint

x2