How critical is piston deck height & quench distance for an LS1?
6600 rpm clutch dump of death Administrator
Joined: Dec 2001
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From: Texas
Originally Posted by 2000RATA
I hate to be a dick but J-Rod you did not write that yourself. That is word for word from I believe SpeedOMotive's website. I'll have to look tonight to be sure. Own up to it, you copied and pasted.
Chris
Chris
6600 rpm clutch dump of death Administrator
Joined: Dec 2001
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From: Texas
Originally Posted by 2000RATA
Like I said I'm not being a dick. I was just trying to razz you a little. I should have used the approiate emoticon to express that. I met you at the shootout. It's all good.
Chris
Chris
Like those????
Don't worry, its all good... 
On The Tree
Joined: Jan 2003
Posts: 167
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From: Fair Oaks, CA
Glad to see you guys have a good handle on this.
I keep quench between .035-.045 max.
& I would also recomend Cometic gaskets. They have gaskets from .025 - .125 thicknesses & will custom make them for your application if neccessary.
I keep quench between .035-.045 max.
& I would also recomend Cometic gaskets. They have gaskets from .025 - .125 thicknesses & will custom make them for your application if neccessary.
I keep quench between .035-.045 max.
& I would also recomend Cometic gaskets. They have gaskets from .025 - .125 thicknesses & will custom make them for your application if neccessary.
& I would also recomend Cometic gaskets. They have gaskets from .025 - .125 thicknesses & will custom make them for your application if neccessary.
On The Tree
Joined: Jan 2003
Posts: 167
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From: Fair Oaks, CA
Originally Posted by John B
93Pony, with this being the case should I even bother decking the block? Should I just get a custom head gasket to obtain the desired 0.035"-0.045" depth and not worry if the pistons are 0.004" in the hole?ghhhh
My new motor has the pistons .005 IN the hole. I bought .035 Cometics to get the right quench.
Which ever way is cheaper IMO....both ways will work.
My pistons ended up being .010 out of the hole, and I run a .041 gasket. Great octane tolerance, zero problems so far with detonation. Motor runs great, despite the poor heads I have on there 
That's what I did.
My new motor has the pistons .005 IN the hole. I bought .035 Cometics to get the right quench.
Which ever way is cheaper IMO....both ways will work.
My new motor has the pistons .005 IN the hole. I bought .035 Cometics to get the right quench.
Which ever way is cheaper IMO....both ways will work.
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On The Tree
Joined: Nov 2005
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Originally Posted by John B
In blueprinting my LS6 short block I noted that the piston sits 0.004" below the deck height and when I combine this with the correct GM head gaskets for my LS6 heads the quench distance appears to be 0.064". This seems awfully high to me for an LS1. Should I be decking the block surface to obtain a positive piston deck height above the block to decrease the quench distance? I plan on running static compression in the 11.8:1 range on pump gas.
Very good info....
Still having a question though.
62cc heads
Mahle -12cc full dish pistons (.008 out of the hole)
Cometic .045" gaskets
402 LQ9
Is quench area less with a full dish piston??
To me, the quench area would be the full volume of each cylinder, regardless of the shape of the piston. But I am also fairly new to this. To me a -12cc full dish piston would have the same quench as -12cc reversed dish piston. Correct me if I am wrong, still learning about quench.
Still having a question though.
62cc heads
Mahle -12cc full dish pistons (.008 out of the hole)
Cometic .045" gaskets
402 LQ9
Is quench area less with a full dish piston??
To me, the quench area would be the full volume of each cylinder, regardless of the shape of the piston. But I am also fairly new to this. To me a -12cc full dish piston would have the same quench as -12cc reversed dish piston. Correct me if I am wrong, still learning about quench.
.040" is certainly plenty with a steel rod, and especially an aluminium block. I have never used more than .036" with steel rods and iron block, I shoot for .032". When everything is dead nuts, nothing touches, and no carbon forms in the squish area. You can angle the deck of the piston a tad and get away with even less. Since aluminium blocks grow taller at temp, you can run them a tad closer (cold). I ran my 4.125" bore aluminium Rodeck block sprint car engines (Carillo rods) with .034" squish (Fel Pros & .002" out). Ran them 8300/8500 RPM all night long, nothing ever touched. Larger bores &/or looser-fit pistons need more room (piston rock), aluminium rods need more room (you know why). I used .038" to .040" squish on my last drag race engines, but those were 9800 rpm 3 7/8" bores and aluminium rods. I have found tighter squish always makes more power. This is all so much easier now that we have gaskets made any thickness we need.
Good luck, Ed
Good luck, Ed
Originally Posted by Mr. Luos
Very good info....
Still having a question though.
62cc heads
Mahle -12cc full dish pistons (.008 out of the hole)
Cometic .045" gaskets
402 LQ9
Is quench area less with a full dish piston??
To me, the quench area would be the full volume of each cylinder, regardless of the shape of the piston. But I am also fairly new to this. To me a -12cc full dish piston would have the same quench as -12cc reversed dish piston. Correct me if I am wrong, still learning about quench.
Still having a question though.
62cc heads
Mahle -12cc full dish pistons (.008 out of the hole)
Cometic .045" gaskets
402 LQ9
Is quench area less with a full dish piston??
To me, the quench area would be the full volume of each cylinder, regardless of the shape of the piston. But I am also fairly new to this. To me a -12cc full dish piston would have the same quench as -12cc reversed dish piston. Correct me if I am wrong, still learning about quench.
Good luck, Ed
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On re-reading this thread, I realize most of us use the words "squish" and "quench" interchangeably, which is not unreasonable, since they describe the same close-clearance region of the combustion chamber. However, apart from confusing anyone new to the concept, there is a subtle assumption baked into these word choices, which I think is misleading: "Squish" tacitly indicates that the operative phenomenon is the ejection of a high speed, turbulence-inducing gas jet from between the head surface and the fast and closely approaching piston, thus increasing turbulence = improved flame speed = reducing spark advance requirements = less negative work on the piston's upstroke and reduced time for detonation to raise its ugly head.
"Quench" on the other hand seems to suggest directly damping out detonation by sucking heat out of the mixture in this sensitive region via a combination of large, relatively cold, metal surfaces and perhaps some turbulence to increase the heat transfer.
My money's on "squish" as the more accurate description. Comments?
"Quench" on the other hand seems to suggest directly damping out detonation by sucking heat out of the mixture in this sensitive region via a combination of large, relatively cold, metal surfaces and perhaps some turbulence to increase the heat transfer.
My money's on "squish" as the more accurate description. Comments?
TECH Regular
Joined: Oct 2005
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Also, I think what Mr. Luos is asking: "Is quench area less with a full dish piston??
To me, the quench area would be the full volume of each cylinder, " relates to how much of the piston/head area is considered quench/squish, i.e., a full dish piston might have only say a 0.300" band of flat horizontal surface around the edge, of which only 1/4 might mate closely with a similar flat head surface, thus the squish area would be ~ (0.3 x 4.0 x Pi)/4 = 0.94 square inches. A partial dish piston might have 2 or more square inches of squish surface.
This raises the interesting question: How much squish area do we want, and how should it be distributed? If there is a lot in one region, there will be a large, high velocity jet, producing lots of turbulence in its path. If the area is similar but distributed all around the piston, it will produce lower velocity jets, but perhaps more net turbulence, due to the colliding streams...
To me, the quench area would be the full volume of each cylinder, " relates to how much of the piston/head area is considered quench/squish, i.e., a full dish piston might have only say a 0.300" band of flat horizontal surface around the edge, of which only 1/4 might mate closely with a similar flat head surface, thus the squish area would be ~ (0.3 x 4.0 x Pi)/4 = 0.94 square inches. A partial dish piston might have 2 or more square inches of squish surface.
This raises the interesting question: How much squish area do we want, and how should it be distributed? If there is a lot in one region, there will be a large, high velocity jet, producing lots of turbulence in its path. If the area is similar but distributed all around the piston, it will produce lower velocity jets, but perhaps more net turbulence, due to the colliding streams...
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
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From: Upstate NY
Originally Posted by MadBill
On re-reading this thread, I realize most of us use the words "squish" and "quench" interchangeably, which is not unreasonable, since they describe the same close-clearance region of the combustion chamber. However, apart from confusing anyone new to the concept, there is a subtle assumption baked into these word choices, which I think is misleading: "Squish" tacitly indicates that the operative phenomenon is the ejection of a high speed, turbulence-inducing gas jet from between the head surface and the fast and closely approaching piston, thus increasing turbulence = improved flame speed = reducing spark advance requirements = less negative work on the piston's upstroke and reduced time for detonation to raise its ugly head.
"Quench" on the other hand seems to suggest directly damping out detonation by sucking heat out of the mixture in this sensitive region via a combination of large, relatively cold, metal surfaces and perhaps some turbulence to increase the heat transfer.
My money's on "squish" as the more accurate description. Comments?
"Quench" on the other hand seems to suggest directly damping out detonation by sucking heat out of the mixture in this sensitive region via a combination of large, relatively cold, metal surfaces and perhaps some turbulence to increase the heat transfer.
My money's on "squish" as the more accurate description. Comments?
T & T list the following desirable characteristics of combustion chambers from the point of view of attaining the highest resistance to detonation:
1. Small bore
2. high velocity through the inlet valve
3. Short ratio of flame path to bore
4. Absence of hot surfaces in the end-gas region
5. Use of squish areas, particularly in the end-gas region.
The point out that 1. and 2. often conflict with the need for high volumetric efficiency, and that they will be chosen by consideratioins other than resistance to detonation.
[The Internal-Combustion Engine by C.F. Taylor and E.S.Taylor]
The most recent Engine Masters Challenges have become an exercise in limiting detonation while making prodigious power and torque. Jon Kaase used the small bore approach quite successfully.
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Joined: Dec 2004
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From: K-W, Ontario
Is it just me, or would we all run 0.000" quench height if we weren't worried
about thermal expansion and mechanical clearance?
I'd rather push everything toward the valves, and keep most of the boom in
the chamber than down in the bore upon ignition.
Isn't it better to add the volume to the chamber when moving the charge from
the quench area? That means SCR stays pretty much the same.
We're just behind the 8 ball because of the cylinder head and valve train design. Which brings on another question about cross flow /hemi heads:
How much less does detonation come into play with an open chamber?
The temperature across the bore would be fairly even in comparison correct?
Maybe an LT-5 head would be better suited for this discussion since it's closer
to home.
about thermal expansion and mechanical clearance?
I'd rather push everything toward the valves, and keep most of the boom in
the chamber than down in the bore upon ignition.
Isn't it better to add the volume to the chamber when moving the charge from
the quench area? That means SCR stays pretty much the same.
We're just behind the 8 ball because of the cylinder head and valve train design. Which brings on another question about cross flow /hemi heads:
How much less does detonation come into play with an open chamber?
The temperature across the bore would be fairly even in comparison correct?
Maybe an LT-5 head would be better suited for this discussion since it's closer
to home.
On The Tree
Joined: Nov 2005
Posts: 184
Likes: 0
Originally Posted by Adrenaline_Z
Is it just me, or would we all run 0.000" quench height if we weren't worried
about thermal expansion and mechanical clearance?
I'd rather push everything toward the valves, and keep most of the boom in
the chamber than down in the bore upon ignition.
Isn't it better to add the volume to the chamber when moving the charge from
the quench area? That means SCR stays pretty much the same.
We're just behind the 8 ball because of the cylinder head and valve train design. Which brings on another question about cross flow /hemi heads:
How much less does detonation come into play with an open chamber?
The temperature across the bore would be fairly even in comparison correct?
Maybe an LT-5 head would be better suited for this discussion since it's closer
to home.
about thermal expansion and mechanical clearance?
I'd rather push everything toward the valves, and keep most of the boom in
the chamber than down in the bore upon ignition.
Isn't it better to add the volume to the chamber when moving the charge from
the quench area? That means SCR stays pretty much the same.
We're just behind the 8 ball because of the cylinder head and valve train design. Which brings on another question about cross flow /hemi heads:
How much less does detonation come into play with an open chamber?
The temperature across the bore would be fairly even in comparison correct?
Maybe an LT-5 head would be better suited for this discussion since it's closer
to home.
so how much is too LITTLE quench generally?
my pistons come out .015 and I have run a .040, .043 and .055 gaskets.
the .040 leave very little, carbon in the quench area. just going to the .043, it leaves a LOT more. but that is only .025 quench for the .040. is that pushing it? I have an iron block and obvioulsy aluminum heads.
my pistons come out .015 and I have run a .040, .043 and .055 gaskets.
the .040 leave very little, carbon in the quench area. just going to the .043, it leaves a LOT more. but that is only .025 quench for the .040. is that pushing it? I have an iron block and obvioulsy aluminum heads.