Compression Issue--LS1
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From: Clear Lake
Compression Issue--LS1 I would like to install a Vortech supercharger on 99 SS/Camaro, However, I hear of problems with LS1 compression ratio being to high, Any way around the compression issue???
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From: Nawf Carolina
Re: Compression Issue--LS1 6 liter heads will lower your compression due to a larger combustion chamber.
Or you can go conservative on the timing, liberal with the octane, get the tune right and still make great power.
J.
Or you can go conservative on the timing, liberal with the octane, get the tune right and still make great power.
J.
Re: Compression Issue--LS1 Thicker heads gaskets are a double edged sword. The thicker they are the lower the CR. However the thicker they are the easier they are to blow or allow the head to move on them.
I really don't recommend them for an FI motor.
I really don't recommend them for an FI motor.
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From: Centrifugal City
Re: Compression Issue--LS1 30% thicker than the cheap paper/lead/whatever stock gaskets using a thicker Multi-Layer Steel shouldn't be an issue. .054"->.078"
I think it's a smart/cheap way to drop .5 pts of Compression & keep stock heads.
I think it's a smart/cheap way to drop .5 pts of Compression & keep stock heads.
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From: Centrifugal City
Re: Compression Issue--LS1 I think the quench argument is BS pushed as paranoia by tuners to sell you overpriced top/bottom ends.
Most mechanics who have know & increased gaskets in the past for many apps laugh when I ask about quench problems at +30% thickness.
I think +70% to +100% of the original thickness and quench could become an issue. But we're not talking about that much.
I drive on this setup N/A as is and my car pulls hard with no problems. For now I've just upped the timing. On paper from 10.1:1 to 9.6:1 I have a 2% power loss. But in Hot/Humid FLA, it might be a better setup anyhow. Waiting for SC. $$
<small>[ July 08, 2002, 09:20 PM: Message edited by: MelloYellow ]</small>
Most mechanics who have know & increased gaskets in the past for many apps laugh when I ask about quench problems at +30% thickness.
I think +70% to +100% of the original thickness and quench could become an issue. But we're not talking about that much.
I drive on this setup N/A as is and my car pulls hard with no problems. For now I've just upped the timing. On paper from 10.1:1 to 9.6:1 I have a 2% power loss. But in Hot/Humid FLA, it might be a better setup anyhow. Waiting for SC. $$
<small>[ July 08, 2002, 09:20 PM: Message edited by: MelloYellow ]</small>
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From: the moon
Re: Compression Issue--LS1 MelloYellow, you really are way off base IMO.
I don't know who you are talking to, but they obviously do not understand what quench is then...IMO.
.078" is a very crappy quench distance.
You are almost to the point it's not even worth running a quench pad and you could just as easily have hogged out the quench pad to drop compression.
Most builders when using a quench head will run the closest possible distance without hitting the piston into the head. This goes for all engines, autos, Bikes, etc.
You may as well just cut your heads up and create a full open chamber if you think quench distance is not that important.After a certain distance it does almost nothing and you lose power and detonation control.
Since you already have your mind made up,
here is some info for others on the subject from KB pistons.There is a ton more info out there on the subject if anybody wants to search.I thought this was a good explanation though.
Excessive cylinder pressure will encourage engine-destroying detonation and no piston is immune to its' effects. An important first step is to set the assembled quench (a.k.a. "squish") distance to .040". The quench distance is the compressed thickness of the head gasket plus the deck clearance (the distance your piston is down in the bore). If your piston height (not dome height) is above the block deck, subtract the overage from the gasket thickness to get a true assembled quench distance. The quench area is the flat part of the piston that would contact a similar flat area on the cylinder head if you had .000" assembled quench height. In a running engine, the .040" quench decreases to a close collision between the piston and cylinder head. The shock wave from the close collision drives air at high velocity through the combustion chamber. This movement tends to cool hot spots, averages the chamber temperature, reduces detonation and increases power.
If you are building an engine with steel rods, tight bearings and pistons, modest RPM and automatic transmission, a .035" quench is the minimum practical to run without engine damage. The closer the piston comes to the cylinder head at operating speed, the more turbulence is generated. Unfortunately, the operating quench height varies in an engine as RPM and temperatures change. If aluminum rods, loose pistons (they rock and hit the head), and over 6000 RPM operation is anticipated, a static clearance of .055" could be required. A running quench height in excess of .060" will forfeit the benefits of the quench head design and can cause severe detonation. The suggested .040" static quench height is recommended as a good usable dimension for stock rod engines up to 6500 RPM. Above 6500 RPM, rod selection becomes important. Since it is the close collision between the piston and the cylinder head that reduces the prospect of detonation, never add a shim or head gasket to lower compression on a quench head engine. If you have 10:1 with a proper quench and then add an extra .040" gasket to give 9.5:1 and .080" quench, you will create more ping at 9.5:1 than you had at 10:1.
Now what I did for my own engine, was to enlarge the stock chambers to 73cc. I am using a .041" gasket.
pistons out of deck .004".
This lowers compression and tightens the quench to the max.
That is the way to go IMO. It'll make more power and have very good detonation control.
Steve
I don't know who you are talking to, but they obviously do not understand what quench is then...IMO.
.078" is a very crappy quench distance.
You are almost to the point it's not even worth running a quench pad and you could just as easily have hogged out the quench pad to drop compression.
Most builders when using a quench head will run the closest possible distance without hitting the piston into the head. This goes for all engines, autos, Bikes, etc.
You may as well just cut your heads up and create a full open chamber if you think quench distance is not that important.After a certain distance it does almost nothing and you lose power and detonation control.
Since you already have your mind made up,
here is some info for others on the subject from KB pistons.There is a ton more info out there on the subject if anybody wants to search.I thought this was a good explanation though.
Excessive cylinder pressure will encourage engine-destroying detonation and no piston is immune to its' effects. An important first step is to set the assembled quench (a.k.a. "squish") distance to .040". The quench distance is the compressed thickness of the head gasket plus the deck clearance (the distance your piston is down in the bore). If your piston height (not dome height) is above the block deck, subtract the overage from the gasket thickness to get a true assembled quench distance. The quench area is the flat part of the piston that would contact a similar flat area on the cylinder head if you had .000" assembled quench height. In a running engine, the .040" quench decreases to a close collision between the piston and cylinder head. The shock wave from the close collision drives air at high velocity through the combustion chamber. This movement tends to cool hot spots, averages the chamber temperature, reduces detonation and increases power.
If you are building an engine with steel rods, tight bearings and pistons, modest RPM and automatic transmission, a .035" quench is the minimum practical to run without engine damage. The closer the piston comes to the cylinder head at operating speed, the more turbulence is generated. Unfortunately, the operating quench height varies in an engine as RPM and temperatures change. If aluminum rods, loose pistons (they rock and hit the head), and over 6000 RPM operation is anticipated, a static clearance of .055" could be required. A running quench height in excess of .060" will forfeit the benefits of the quench head design and can cause severe detonation. The suggested .040" static quench height is recommended as a good usable dimension for stock rod engines up to 6500 RPM. Above 6500 RPM, rod selection becomes important. Since it is the close collision between the piston and the cylinder head that reduces the prospect of detonation, never add a shim or head gasket to lower compression on a quench head engine. If you have 10:1 with a proper quench and then add an extra .040" gasket to give 9.5:1 and .080" quench, you will create more ping at 9.5:1 than you had at 10:1.
Now what I did for my own engine, was to enlarge the stock chambers to 73cc. I am using a .041" gasket.
pistons out of deck .004".
This lowers compression and tightens the quench to the max.
That is the way to go IMO. It'll make more power and have very good detonation control.
Steve
