LA360 compression

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Here's the thing........if you go up much on the compression, you're gonna be fighting detonation with that small cam. Just one more thing to think about.
 
RustyRatRod said:
The piston "upgrade" is not an upgrade at all. There are two main pistons for the 360. Flat top and dished. The dished has a taller compression height and basically has the same compression. Although it sits higher in the bore at TDC, it has a dish, which reduces compression. The flat top has a shorter compression height and no dish. There are essentially different types of pistons that achieve basically the same thing. Different year model pistons. There WAS a 1971 only piston from Chrysler that was a flat top and near zero deck height that had an actual 9:1 compression for the 71 only model year, but those pistons are impossible to find in the aftermarket now. You DO NOT have a high compression piston, so stop digging for it. I don't understand your reasoning for returning the heads at all, as you've been told time and again that a low compression engine can be built to run and run strong. You're just not listening. It's your baby though, so have at it.
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You quoted me but are speaking to the OP. I was merely pointing out what I found. I agree with you 100%.
 
TT5.9mag said:
You quoted me but are speaking to the OP. I was merely pointing out what I found. I agree with you 100%.
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My bad. Sorry, I got precious little sleep last night.
 
TT5.9mag said:
He’s wrong
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...and thing is, they aren't REAL FAR off. He COULD see 9:1 with the .019" steel head gaskets and maybe a light mill.......he might not even need the mill. It would be close. I'd run it at what I figured which was 8.4. It'll run good. Probably better than good.
 
If it was me I would be inclined to return the CNC heads and swap them for the regular 63cc speedmasters to gain some compression back. (Assuming they are in stock). They will flow good enough for what you are doing and give you a good bump in compression.
 
Ted265 said:
If it was me I would be inclined to return the CNC heads and swap them for the regular 63cc speedmasters to gain some compression back. (Assuming they are in stock). They will flow good enough for what you are doing and give you a good bump in compression.
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That would have my endorsement with more camshaft.
 
RustyRatRod said:
...and thing is, they aren't REAL FAR off. He COULD see 9:1 with the .019" steel head gaskets and maybe a light mill.......he might not even need the mill. It would be close. I'd run it at what I figured which was 8.4. It'll run good. Probably better than good.
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There’s no doubt that at 8.4 it could run good. And it’ll probably make ~300hp and most of us know what that’ll do in an abody. But early on he stated his goal of 400-450hp and he ain’t gettin there by just dropping on a set of OOTB heads and a mild cam.
 
TT5.9mag said:
There’s no doubt that at 8.4 it could run good. And it’ll probably make ~300hp and most of us know what that’ll do in an abody. But early on he stated his goal of 400-450hp and he ain’t gettin there by just dropping on a set of OOTB heads and a mild cam.
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Nope.
 
RustyRatRod said:
There would have been no way I would have sent those heads back. Those were that engine's only chance at any decent power using those pistons, IMO. Flow trumps compression in "that" particular instance, IMO. But it's your deal, so carry on.
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Lower compression does not hurt horsepower that much... It has a greater influence on efficiency...

Rob is right, flow trumps compression for power output...
 
If you throw a set of 66 - 67 920 casting heads on it and a .040" thick head gasket, you can increase compression about 0.9 points...
 
KB 107 after a couple of deck clean ups over the years, these pistons would work good with your SM heads

IMG_1755.jpg
 
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