Thinnest head gasket I can use stock bottom ls1
12-30-2018, 11:38 PM
#23
I run a .036 for better quench on a newish 4.030 bore, 4.1 stroke supposedly not well supported pistons lol with 0 deck. Its a used stock un surfaced Gto block. .005 out corner to corner from core shift. No witness marks and no issues after 3 years. Doing it again with a new 426 CID ls3 block. You really should check your heads and block surfaces closely though..... Stock pistons can be all over the place and .008 out of the hole too. You have to check all of that. As far as detonation the timing is adjustable but a half a point of compression should be fine.
Last edited by handyandy496; 12-31-2018 at 12:03 AM.
02-06-2019, 05:24 PM
#25
Most can't that have stock engines.
Some people have built motors where the piston height is different and can run an even thinner gasket. For example most stock motors have a piston out of the hole height around .007 or so. Sometimes with strokers you may end up at a 0 deck height or under.
Also part of the issue to watch out for is heat expansion and rod stretch, different materials stretch and grow at different rates so some that have other than stock components need to build accordingly for that.
02-06-2019, 07:03 PM
#28
I run a .040" on my motor shifting at 7400. If it's hit, it hasn't blown the car up in over 5 years.
But I think ideally a .035"-040" quench is what you want on an NA configuration (so a .040 or .045" gasket works perfect with the .006" out of the hole stock piston). And .050-.060" on nitrous or boost to reduce flame travel speed and allow for more timing.
I actually plan to run a .040" on a zero deck block for my next build because of 7500+ RPM. Need to account for rod stretch with heavier pistons.
But I think ideally a .035"-040" quench is what you want on an NA configuration (so a .040 or .045" gasket works perfect with the .006" out of the hole stock piston). And .050-.060" on nitrous or boost to reduce flame travel speed and allow for more timing.
I actually plan to run a .040" on a zero deck block for my next build because of 7500+ RPM. Need to account for rod stretch with heavier pistons.
02-06-2019, 07:05 PM
#29
TECH Senior Member
Most can't that have stock engines.
Some people have built motors where the piston height is different and can run an even thinner gasket. For example most stock motors have a piston out of the hole height around .007 or so. Sometimes with strokers you may end up at a 0 deck height or under.
Also part of the issue to watch out for is heat expansion and rod stretch, different materials stretch and grow at different rates so some that have other than stock components need to build accordingly for that.
Some people have built motors where the piston height is different and can run an even thinner gasket. For example most stock motors have a piston out of the hole height around .007 or so. Sometimes with strokers you may end up at a 0 deck height or under.
Also part of the issue to watch out for is heat expansion and rod stretch, different materials stretch and grow at different rates so some that have other than stock components need to build accordingly for that.
02-07-2019, 02:36 PM
#32
Edit: above where I wrote most stock motors the piston is out of the hole around .007, I meant LS motors.
I left it a bit vague so in case it helps..
When you adjust your headgasket thickness you change two things. Compression and quench.
Focusing on quench..
Quench is the space between the flat on the piston near the edge if its dome or dish, or the entire piston if it's a flat top and the quench pad on the cylinder head (the flat part of the cylinder head chamber that is above the piston) (to go further some heads don't have a quench pad). Looking at an LS head it's heart shaped basically, if it were completely round it wouldn't have a quench pad and you wouldn't have quench distance to worry about. You'd still have clearances to worry about but to get onto it and discuss quench on LS applications...
On LS motors the piston comes up and out of the cylinder a little bit. If it came to exactly flush with the block deck/top of the cylinder that would be zero deck. LS pistons come up about .006-.008. I use .007 some use .006 whatever. If the block deck has had any material removed the piston will come out higher. If you have done a stroker with different stroke or rod length or different pistons or changed wrist pin height you may see a different number and end up with the piston higher, at zero or even below the deck surface of the block. Then you need to use the new piston height to measure quench.
So since the heads quench pad is equal to the surface of the head you never need to take a measurement, it's just a zero. So the head gasket thickness and piston out of the hole is the info you need to calculate to find quench. Since the piston is up and out a little you subtract that from the headgasket thickness to get your quench measurement, since the piston is technically coming up into the headgasket space. If you had a piston .005 up and out of the cylinder and a .040 head gasket you would have .035 quench distance.
.0000 quench is the piston touching the head, and rods stretch at high rpm, metal expands, we accidentally over rev etc so we need a cushion there. The general rule for that cushion on your standard street motor is in the mid 30's. So most aim for quench somewhere in the 30's. Specially built engines can do different things based on rod material (aluminum or steel) the rpm they expect to see etc.
There's quite a bit more to it actually beyond that but it's getting real specific (like how much quench do you want for your particular build based on power adders) but that should get you guys to where you understand it well enough.
I left it a bit vague so in case it helps..
When you adjust your headgasket thickness you change two things. Compression and quench.
Focusing on quench..
Quench is the space between the flat on the piston near the edge if its dome or dish, or the entire piston if it's a flat top and the quench pad on the cylinder head (the flat part of the cylinder head chamber that is above the piston) (to go further some heads don't have a quench pad). Looking at an LS head it's heart shaped basically, if it were completely round it wouldn't have a quench pad and you wouldn't have quench distance to worry about. You'd still have clearances to worry about but to get onto it and discuss quench on LS applications...
On LS motors the piston comes up and out of the cylinder a little bit. If it came to exactly flush with the block deck/top of the cylinder that would be zero deck. LS pistons come up about .006-.008. I use .007 some use .006 whatever. If the block deck has had any material removed the piston will come out higher. If you have done a stroker with different stroke or rod length or different pistons or changed wrist pin height you may see a different number and end up with the piston higher, at zero or even below the deck surface of the block. Then you need to use the new piston height to measure quench.
So since the heads quench pad is equal to the surface of the head you never need to take a measurement, it's just a zero. So the head gasket thickness and piston out of the hole is the info you need to calculate to find quench. Since the piston is up and out a little you subtract that from the headgasket thickness to get your quench measurement, since the piston is technically coming up into the headgasket space. If you had a piston .005 up and out of the cylinder and a .040 head gasket you would have .035 quench distance.
.0000 quench is the piston touching the head, and rods stretch at high rpm, metal expands, we accidentally over rev etc so we need a cushion there. The general rule for that cushion on your standard street motor is in the mid 30's. So most aim for quench somewhere in the 30's. Specially built engines can do different things based on rod material (aluminum or steel) the rpm they expect to see etc.
There's quite a bit more to it actually beyond that but it's getting real specific (like how much quench do you want for your particular build based on power adders) but that should get you guys to where you understand it well enough.
Last edited by 00pooterSS; 02-07-2019 at 02:46 PM.