compression advice
01-08-2006, 10:17 AM
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compression advice Various forms of these questions have been asked many times before, and checking the search gives several sticky threads that really cloud the question, so I'll just ask straight out. 
I have a stock bore LS1 with a set of 62cc Dart heads that I am cleaning up. The final CC will proably be around 63 after the clean up, and polishing work.
1.If I run a stock MLS 6.0 gasket, what will I have to mill (if any) to get my CR between 10.9-11.0.
2. I'm running a 224 /568 cam. Will I have any PV issues?
3. Will I be OK with 93 octane gas, or should I back the CR down to around 10.7-10.8?
Thanks
I have a stock bore LS1 with a set of 62cc Dart heads that I am cleaning up. The final CC will proably be around 63 after the clean up, and polishing work.
1.If I run a stock MLS 6.0 gasket, what will I have to mill (if any) to get my CR between 10.9-11.0.
2. I'm running a 224 /568 cam. Will I have any PV issues?
3. Will I be OK with 93 octane gas, or should I back the CR down to around 10.7-10.8?
Thanks
01-08-2006, 10:27 AM
#2
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1- http://www.rbracing-rsr.com/compstaticcalc.html
2- You shouldn't have PTV issues.
3- Yes 93 will be fine, professional wideband tuning is a must.
Keep SCR to have a 8.5/8.6 DCR
2- You shouldn't have PTV issues.
3- Yes 93 will be fine, professional wideband tuning is a must.
Keep SCR to have a 8.5/8.6 DCR
01-08-2006, 11:16 AM
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I would shoot for 11.3 on 93 gas.
First I would lower compression using a thinner head gasket 0.40, then mill head about .012 to 60cc, that should do it ( this would total .025 less PTV and put you around 11.3)
You should first do some checking to ensure that you would have good PTV
First I would lower compression using a thinner head gasket 0.40, then mill head about .012 to 60cc, that should do it ( this would total .025 less PTV and put you around 11.3)
You should first do some checking to ensure that you would have good PTV
01-08-2006, 12:04 PM
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I WOULD'NT do that. First off if you go with thinner head gaskets the compression will go up because you've moved the combustion chambers closer to the pistons which decreases the area thus increasing the compression and then if you mill the heads on top of that the compresssion will go up once again. A thicker head gasket moves the combustion chambers further away from the top of the piston thus lowering the compression.
Originally Posted by SlickVert
I would shoot for 11.3 on 93 gas.
First I would lower compression using a thinner head gasket 0.40, then mill head about .012 to 60cc, that should do it ( this would total .025 less PTV and put you around 11.3)
You should first do some checking to ensure that you would have good PTV
First I would lower compression using a thinner head gasket 0.40, then mill head about .012 to 60cc, that should do it ( this would total .025 less PTV and put you around 11.3)
You should first do some checking to ensure that you would have good PTV
01-08-2006, 04:18 PM
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Thanks for the input guys;
The reason I was basing my setup on a "stock" 6.0 gaskets is;
1. Everyone seems to think that the stock MLS gaskets are as reliable as anything made and they are dirt cheap compared to some of the aftermarket gaskets. I just don't see spending extra money if it's not needed
2. Dart is recommening the 6.0 gaskets for their head, so the stock MLS seemed the easiest route.
I realize the thinner gaskets (.40) reduce the qench area, thus making (in theory) more HP, but the benifits don't seem to be worth the cost.
I am not trying to run the aboslute highest CR I can, I just want to have the highest I can run safely on pump gas (which is occasially 92) I am NOT trying to build a race car, just a very fast, fun and reliable street car that wil see the track maybe 3 times a year. I've had a couple of cars that had to be fed a regular diet of octane booster just to cruise, and I NEVER want that again
Thanks guys
The reason I was basing my setup on a "stock" 6.0 gaskets is;
1. Everyone seems to think that the stock MLS gaskets are as reliable as anything made and they are dirt cheap compared to some of the aftermarket gaskets. I just don't see spending extra money if it's not needed
2. Dart is recommening the 6.0 gaskets for their head, so the stock MLS seemed the easiest route.
I realize the thinner gaskets (.40) reduce the qench area, thus making (in theory) more HP, but the benifits don't seem to be worth the cost.
I am not trying to run the aboslute highest CR I can, I just want to have the highest I can run safely on pump gas (which is occasially 92) I am NOT trying to build a race car, just a very fast, fun and reliable street car that wil see the track maybe 3 times a year. I've had a couple of cars that had to be fed a regular diet of octane booster just to cruise, and I NEVER want that again
Thanks guys
01-08-2006, 08:18 PM
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.040 head gasket will put your quench area around .032 with stock bottom. That will reduce your quench area that will reduce the tendency to detonate and increase TQ and HP.
Any engine builder will tell you to do this first then look at milling the head for the desired compression.
Any engine builder will tell you to do this first then look at milling the head for the desired compression.
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01-08-2006, 11:16 PM
#8
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1- Milling the head will reduce head flow (so first use gasket then mill as little as possible if needed)
2- As mentionned a thinner gasket will tighten the quench and reduce detonnation, which is a + for higher SCR. Safe and good street quench range is .033>.040
3- with 92+ Octane you can run to 11.5 SCR with no issue, it is in the tune.
4- 11.0>11.2 SCR is the preferred range of LSX motors.
5- Look at your DCR (Dynamic Compression Ratio), much more important than SCR.
6- 1 step colder plug desired for 11.0:1 (TR6 or similar) with shorter gap.
2- As mentionned a thinner gasket will tighten the quench and reduce detonnation, which is a + for higher SCR. Safe and good street quench range is .033>.040
3- with 92+ Octane you can run to 11.5 SCR with no issue, it is in the tune.
4- 11.0>11.2 SCR is the preferred range of LSX motors.
5- Look at your DCR (Dynamic Compression Ratio), much more important than SCR.
6- 1 step colder plug desired for 11.0:1 (TR6 or similar) with shorter gap.
01-09-2006, 03:14 PM
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1- Milling the head will reduce head flow (so first use gasket then mill as little as possible if needed)
.040 head gasket will put your quench area around .032 with stock bottom. That will reduce your quench area that will reduce the tendency to detonate and increase TQ and HP.
Any engine builder will tell you to do this first then look at milling the head for the desired compression.
That's good stuff. I was not aware that milling a head affected it's flow, and that using a thinner gasket was beter than milling the head. If that's the case, I can proably just go with a .040 gasket and not worry about having the heads milled.
A 62cc head and .040 gasket should give me around 11-1.
Does anyone have a part # for some 6.0 gaskets that are .040? (and vendor)
.040 head gasket will put your quench area around .032 with stock bottom. That will reduce your quench area that will reduce the tendency to detonate and increase TQ and HP.
Any engine builder will tell you to do this first then look at milling the head for the desired compression.
That's good stuff. I was not aware that milling a head affected it's flow, and that using a thinner gasket was beter than milling the head. If that's the case, I can proably just go with a .040 gasket and not worry about having the heads milled.
A 62cc head and .040 gasket should give me around 11-1.
Does anyone have a part # for some 6.0 gaskets that are .040? (and vendor)
