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Top piston ring gap - whats really required?

General engine tech -- Drag Racing to Circle Track

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CGT
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Re: Top piston ring gap - whats really required?

Post by CGT »

Screenshot (39).png
2018 Supercharged LT4 mechanical specifications. 650hp supercharged. Not uncommon for these to be making several hundred more horsepower than that on the stock shortblock….And could have .009 top ring end gap. I could never get myself to run ring end gaps like that, but it makes you wonder.
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jed
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Re: Top piston ring gap - whats really required?

Post by jed »

As I have said before just because it is published it doesn't mean that's what they come with.
When you measure a new engine and the engine has got .009 then I'll be more receptive of factory published tolerances.
CGT
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Re: Top piston ring gap - whats really required?

Post by CGT »

jed wrote: Mon Oct 12, 2020 2:39 pm As I have said before just because it is published it doesn't mean that's what they come with.
When you measure a new engine and the engine has got .009 then I'll be more receptive of factory published tolerances.
True. Im not soliciting to anyone or myself to run .009, but it wouldn't surprise me if they are. Many of the other listed tolerances have been very very close. That .009 to .0015 tolerance may be what makes the difference between the factory short blocks that live with power adders, and the ones that don't....either way that's tight! I'll have to keep my eyes peeled for an opportunity to check ring end gap on a new production LS.
engineguyBill
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Re: Top piston ring gap - whats really required?

Post by engineguyBill »

Combustion heat is transferred through the piston top to the piston ring, then through the ring to the cylinder wall, to the coolant jacket. Real-world testing has shown that ring gap is not critical in developing torque/horsepower - AS LONG AS MINUMUM GAP SPECS ARE RECOGNIZED AND FOLLOWED. In other words a race engine with .018" gap will not necessarily produce more horsepower than the same engine with .024" or .026" gap.
Bill

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digger
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Re: Top piston ring gap - whats really required?

Post by digger »

risk vs reward
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