Blown head gasket? How to lower CR?
Blown head gasket? How to lower CR? My friend's supercharged Mallett 435 Vette is overheating and spewing coolant. We checked the cooling system, replaced water pump, even ran the car without a thermostat and it still overheats. No water in oil but we are kind of thinking that the coolant is getting pressurized.
The car has the standard Mallett 435 package with the supercharger (about 10psi. I think is has a normal CR of almost 11 to 1. What head gaskets should we use that are strong and will lower the CR just a tad. Does Cosmetic make something?
I tried search and it doesn't seem to work...
George
The car has the standard Mallett 435 package with the supercharger (about 10psi. I think is has a normal CR of almost 11 to 1. What head gaskets should we use that are strong and will lower the CR just a tad. Does Cosmetic make something?
I tried search and it doesn't seem to work...
George
That compression is pretty high for a SC in my opinion....
From the sound of it you have a blown head gasket...
What is the bore now?? Pistons?? Head Chamber siz in cc's??
Was the car Detinating???
From the sound of it you have a blown head gasket...
What is the bore now?? Pistons?? Head Chamber siz in cc's??
Was the car Detinating???
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From: Norn Iron
With such a high CR...if the gasket has failed, its more a symtom of problems with the setup, rather that the gasket itself.
Stock GM MLS gaskets are hard to beat, and are very well proven.
Ideally you want a very safe tune, and slightly lower CR if you can get it somehow.
Stock GM MLS gaskets are hard to beat, and are very well proven.
Ideally you want a very safe tune, and slightly lower CR if you can get it somehow.
I think it is a Vortech blower. There is no intercooler.
It is a stock bore but all forged with a 3.9" stroke. The CR is stock or slightly higher. The car is a 1999. Here is the link to the package:
http://www.mallettcars.com/c5-435conversion.htm
and it also has the supercharger option amongst others.
Here is a picture of what it looks like:
http://www.mallettcars.com/images/c5-435engine.jpg
The car is used for roadracing and it has had a tune done. It is tuned for 93 pump but he always runs 1/2 race gas when on the track. We have never heard any detonation. The car runs hot no doubt and could use less compression. Right now there is very little timing due to the high compression and it makes about 550RWHP. It also has Meth injection right now.
So is there a head gasket that will lower the CR a little and also strong? Or is the stock ones best.
I think longer term we will be replacing the heads with a set of 317 heads or another 72cc chamber option but we hope that the gasket is blown and we can get it running again short term.
George
It is a stock bore but all forged with a 3.9" stroke. The CR is stock or slightly higher. The car is a 1999. Here is the link to the package:
http://www.mallettcars.com/c5-435conversion.htm
and it also has the supercharger option amongst others.
Here is a picture of what it looks like:
http://www.mallettcars.com/images/c5-435engine.jpg
The car is used for roadracing and it has had a tune done. It is tuned for 93 pump but he always runs 1/2 race gas when on the track. We have never heard any detonation. The car runs hot no doubt and could use less compression. Right now there is very little timing due to the high compression and it makes about 550RWHP. It also has Meth injection right now.
So is there a head gasket that will lower the CR a little and also strong? Or is the stock ones best.
I think longer term we will be replacing the heads with a set of 317 heads or another 72cc chamber option but we hope that the gasket is blown and we can get it running again short term.
George
Last edited by ibjamin; Jul 16, 2007 at 08:50 PM. Reason: Added link to photo
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Not sure what other info. I don't have my laptop here with the EFILIVE but I think it has like 10-14 deg timing max. Rev limiter is set at 6300. The heads are ported and it has stock size valves, the cam is mild, like a 224/228 with .560 lift or so.
He also has ARP studs which I'm wondering if they could be a factor. I hear they have to be tightened and loosened 5 times before you can call it good (using moly lube) and then after they go through a heat cycle they should be re-torqued again.
He also has ARP studs which I'm wondering if they could be a factor. I hear they have to be tightened and loosened 5 times before you can call it good (using moly lube) and then after they go through a heat cycle they should be re-torqued again.
Back up top.
Also, with regards to MLS or Cosmetic, etc gaskets: the heads are from a 99. If the heads have those casting notches in the perimeter of the head is this all a moot point? If they have those notches do I have to use the GM graphite ones or are there MLS ones available that will work with those notches?
George
Also, with regards to MLS or Cosmetic, etc gaskets: the heads are from a 99. If the heads have those casting notches in the perimeter of the head is this all a moot point? If they have those notches do I have to use the GM graphite ones or are there MLS ones available that will work with those notches?
George
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From: Norn Iron
Originally Posted by ibjamin
He also has ARP studs which I'm wondering if they could be a factor. I hear they have to be tightened and loosened 5 times before you can call it good (using moly lube) and then after they go through a heat cycle they should be re-torqued again.
I torqued my last ones just the once, and they lasted well over a year.
Originally Posted by ibjamin
Back up top.
Also, with regards to MLS or Cosmetic, etc gaskets: the heads are from a 99. If the heads have those casting notches in the perimeter of the head is this all a moot point? If they have those notches do I have to use the GM graphite ones or are there MLS ones available that will work with those notches?
George
Also, with regards to MLS or Cosmetic, etc gaskets: the heads are from a 99. If the heads have those casting notches in the perimeter of the head is this all a moot point? If they have those notches do I have to use the GM graphite ones or are there MLS ones available that will work with those notches?
George
Pulled the heads and the gaskets definitely show signs of leakage. They were the stock Graphite ones. That is good news since it explains the overheating. The other good news is that the heads don't have the notches in the edges. We are going to use the GM MLS gaskets for the LS6 engine. Can't beat the price of like $50 for a pair.
The head studs also weren't seated tight in the bottom of the bolt holes so that may also have been a factor. Very little residue from the gaskets is on the block and heads so that also indicates that they weren't sealed very well. A few years ago when I did my Camaro, the gaskets pratically disintegrated when removing the heads.
George
The head studs also weren't seated tight in the bottom of the bolt holes so that may also have been a factor. Very little residue from the gaskets is on the block and heads so that also indicates that they weren't sealed very well. A few years ago when I did my Camaro, the gaskets pratically disintegrated when removing the heads.
George
Go with the mls gaskets, arp studs and lq9 heads while you have them off anyway. It's working great for me so far @ 13psi. You can get a set of used lq9 heads for cheap, like $300 on ebay and they are well worth it. You may also want to consider some type of intercooler.
