LS3 head gasket thickness
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LS3 head gasket thickness Looking at fly cutting our LS3 pistons and have been advised to have heads milled .035" and use Cometic .040" head gaskets.
Is there any reason that I can't use factory or aftermarket .051" head gaskets and simply have the heads machined .046"?
Is there any reason that I can't use factory or aftermarket .051" head gaskets and simply have the heads machined .046"?
those seem like pretty aggressive spec for the heads who told you to do that?
and no milling from the head and gasket are very different. they will both provide the same compression. but milling too much from the head can creat hotspots and increase the chances for detonation along with shrouding the valves depending on how low you go.
decreasing gasket thickness will increase quench which will actually fight detonation and improve combustion along with providing the same compression
and no milling from the head and gasket are very different. they will both provide the same compression. but milling too much from the head can creat hotspots and increase the chances for detonation along with shrouding the valves depending on how low you go.
decreasing gasket thickness will increase quench which will actually fight detonation and improve combustion along with providing the same compression
Yes cutting the head is not always the best idea. I got lucky with just using a .036 gasket for 11.8 compression with 11.6 pistons. This way I get good quenching, less chance of detonation and can run pump gas with a spect cam.
If you do run thinner than .040 gaskets watch your piston to head clearances(or squish dimension). Watch for your cyl that has the tightest clearance and remember aluminum blocks expand .010 when there hot. The piston expands also but only about .004 or so.
Also.....I'd look to run gaskets no thicker than .040". That would bring 'quench' to about .035" which is perfect for a street engine.
KW
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This isn't rocket surgery, gentlemen...
Measure how much the pistons are above or below deck! Don't be lazy/cheap/stupid.
The target is .035 - .045 squish/quench, favoring the lesser.
So... Take .040 (half way between .035 and .045) and subtract whatever empirical measurement you get from your assembled shortblock. That's the correct thickness of gasket to use.
Whatever static compression ratio you end up with is whatever it is. Proper squish is more important than any amount of compression ratio change that you can achieve with differing thickness head gaskets.
Measure how much the pistons are above or below deck! Don't be lazy/cheap/stupid.
The target is .035 - .045 squish/quench, favoring the lesser.
So... Take .040 (half way between .035 and .045) and subtract whatever empirical measurement you get from your assembled shortblock. That's the correct thickness of gasket to use.
Whatever static compression ratio you end up with is whatever it is. Proper squish is more important than any amount of compression ratio change that you can achieve with differing thickness head gaskets.
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Have been running this for several years.
Looking to gain a bit of compression hence the need to flycut.
This isn't rocket surgery, gentlemen...
Measure how much the pistons are above or below deck! Don't be lazy/cheap/stupid.
The target is .035 - .045 squish/quench, favoring the lesser.
So... Take .040 (half way between .035 and .045) and subtract whatever empirical measurement you get from your assembled shortblock. That's the correct thickness of gasket to use.
Whatever static compression ratio you end up with is whatever it is. Proper squish is more important than any amount of compression ratio change that you can achieve with differing thickness head gaskets.
Measure how much the pistons are above or below deck! Don't be lazy/cheap/stupid.
The target is .035 - .045 squish/quench, favoring the lesser.
So... Take .040 (half way between .035 and .045) and subtract whatever empirical measurement you get from your assembled shortblock. That's the correct thickness of gasket to use.
Whatever static compression ratio you end up with is whatever it is. Proper squish is more important than any amount of compression ratio change that you can achieve with differing thickness head gaskets.
Btw .035-.040 quench isnt bad but its not optimal. Optimal would be much closer to .035. The lower numerical quench the better. The problem you run into is the piston smacking the heads. An ls piston stock is about .007 out of the hole so using a .040 gasket like most do on a stock engine yields .033 of quench. I'm currently running that exact setup with no issues.
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I never even so much as implied that anyone should just let compression fall where it may.
The spectrum of change available to you by doing nothing more than changing the thickness of gasket is inconsequential in comparison to having proper squish.
Piston design and combustion chamber volume are how you manipulate static compression ratio, not head gaskets.
And I am quite sure I specified that .035 was favored over .045, as being closer to optimal. I just don't want to steer anyone too close to the edge.
The spectrum of change available to you by doing nothing more than changing the thickness of gasket is inconsequential in comparison to having proper squish.
Piston design and combustion chamber volume are how you manipulate static compression ratio, not head gaskets.
And I am quite sure I specified that .035 was favored over .045, as being closer to optimal. I just don't want to steer anyone too close to the edge.
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$200 is too much to spend on closer to optimal quench? By that logic, hollow stem valves are probably too expensive for closer to optimal valve control, too. I was always under the impression that it's actually cheaper in the long run to do it right the first time. Your build, your money, though. Good luck in whatever you choose.
If he wants to get to a target compression there's no problem in doing so. I would never let static compression just "fall where it may" figure out what compression you want and play with the values to get a good quench and agood mill from the heads. as long as you dont cut too much off its fine
Btw .035-.040 quench isnt bad but its not optimal. Optimal would be much closer to .035. The lower numerical quench the better. The problem you run into is the piston smacking the heads. An ls piston stock is about .007 out of the hole so using a .040 gasket like most do on a stock engine yields .033 of quench. I'm currently running that exact setup with no issues.
Btw .035-.040 quench isnt bad but its not optimal. Optimal would be much closer to .035. The lower numerical quench the better. The problem you run into is the piston smacking the heads. An ls piston stock is about .007 out of the hole so using a .040 gasket like most do on a stock engine yields .033 of quench. I'm currently running that exact setup with no issues.
$200 is too much to spend on closer to optimal quench? By that logic, hollow stem valves are probably too expensive for closer to optimal valve control, too. I was always under the impression that it's actually cheaper in the long run to do it right the first time. Your build, your money, though. Good luck in whatever you choose.
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The change in static compression that would result from going to a .040" gasket when previously using a .051" gasket would be negligible and probably won't be quantifiable on the dyno. However, the engine's resistance to detonation may be closer to optimal, allowing you to either save money at the pump buying a lower octane fuel, providing quite the return on investment. Or the better quench allows you to add more timing using whatever octane fuel you already were using, and thusly your return on investment comes in the form of whatever benefits the additional spark advance provides you with.
Hollow stem intake valves reduce moving mass. Their return on investment comes in the form of less valvetrain wear, saving money on springs. And extra rpm potential do to increased stability, which is a return on investment in the form of whatever benefits the additional rpms may provide you with.
Both hollow stems and proper squish have the potential to save money and the potential to increase power. Looks like both share an equal return on investment...
Hollow stem intake valves reduce moving mass. Their return on investment comes in the form of less valvetrain wear, saving money on springs. And extra rpm potential do to increased stability, which is a return on investment in the form of whatever benefits the additional rpms may provide you with.
Both hollow stems and proper squish have the potential to save money and the potential to increase power. Looks like both share an equal return on investment...
The change in static compression that would result from going to a .040" gasket when previously using a .051" gasket would be negligible and probably won't be quantifiable on the dyno. However, the engine's resistance to detonation may be closer to optimal, allowing you to either save money at the pump buying a lower octane fuel, providing quite the return on investment. Or the better quench allows you to add more timing using whatever octane fuel you already were using, and thusly your return on investment comes in the form of whatever benefits the additional spark advance provides you with.
Hollow stem intake valves reduce moving mass. Their return on investment comes in the form of less valvetrain wear, saving money on springs. And extra rpm potential do to increased stability, which is a return on investment in the form of whatever benefits the additional rpms may provide you with.
Both hollow stems and proper squish have the potential to save money and the potential to increase power. Looks like both share an equal return on investment...
Hollow stem intake valves reduce moving mass. Their return on investment comes in the form of less valvetrain wear, saving money on springs. And extra rpm potential do to increased stability, which is a return on investment in the form of whatever benefits the additional rpms may provide you with.
Both hollow stems and proper squish have the potential to save money and the potential to increase power. Looks like both share an equal return on investment...