Is .020 out of the hole safe for stock pistons?
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I want to mill my block to get the pistons to sit .020 out of the hole. I will be using the stock GM MLS gaskets so the quench area should be about .035, I believe. Is it safe to run the stock pistons .020 out of the hole?
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Thats very far out of the hole. The piston ring may come out of the hole which you dont want. If you want .035 quench why not just run a .040 gasket and call it a day, the hell with milling the block
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Originally Posted by brad8266
Thats very far out of the hole. The piston ring may come out of the hole which you dont want. If you want .035 quench why not just run a .040 gasket and call it a day, the hell with milling the block
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Originally Posted by brad8266
If you want .035 quench why not just run a .040 gasket and call it a day, the hell with milling the block
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It's much easier to remove the thickness from the gasket than the block. I'd imagine the only reason you are asking is because you must have the engine completely torn apart.
Do you want to run the MLS gaskets that bad, or is there another reason?
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Originally Posted by hammertime
Do you want to run the MLS gaskets that bad, or is there another reason?
The top part of the first ringland is at least .125" away from the top of the stock piston, so I don't think that will be a problem. I more wanted to know if sticking the piston that far out of the hole will cause an instability problem.
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Originally Posted by Quick Double Nickel
Yes, the engine is completely torn down. And yes I want to run the MLS gaskets, over say the Cometics, becasue 1) I can get them pretty damn cheap, and 2) I've heard (through this board) that they are a lot easier to install and deal with not-so-perfect deck surfaces a lot better than the Cometics. The engine is going in a daily driver and I don't want to run into the problems with the Cometics.
The top part of the first ringland is at least .125" away from the top of the stock piston, so I don't think that will be a problem. I more wanted to know if sticking the piston that far out of the hole will cause an instability problem.
The top part of the first ringland is at least .125" away from the top of the stock piston, so I don't think that will be a problem. I more wanted to know if sticking the piston that far out of the hole will cause an instability problem.
1) Deck surface on the block should be plenty thick, but you could run short on room if another rebuild requires decking later.
2) If you are running boost or N20, the .025 thicker deck may give marginally more strength for gasket retention
3) You will be creating a larger 'crevice volume' around the head of the piston, basically inside the gasket surface. I would think it should still be so marginally small as not to matter, but there is a possibliity of increased emissions and increased sensativity to detonation.
Personally, I would opt to have the deck surface honed smooth for better gasket sealing, run the .040 or .045 Cometic as required with the amount of material removed, and save room for resurfacing later if needed.
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I thought I read somewhere that the Cometics require a certain level of "smoothness" that's measured in some sort of industry standard, just like the hardness scale of heat treatment. Does anybody know what that is?
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Originally Posted by Quick Double Nickel
I thought I read somewhere that the Cometics require a certain level of "smoothness" that's measured in some sort of industry standard, just like the hardness scale of heat treatment. Does anybody know what that is?
I have cometics sprayed weith 2 coats and they havent had a single leak. The cleaning was easy to do.