GM versus Aftermarket head gasket
01-02-2005, 10:38 PM
#21
Originally Posted by Beast96Z
I can't give you an exact power figure, but why would people put a standardazation a quench area if it weren't meant to be met? There are 1 million and 1 things that could effect horsepower through given quenches. A car with a proper burn pattern will always run better than a car that isn't set-up correctlly. JRP used FFHP heads and you don't see him with the GM gaskets. The point is, is that if you take the time to set-up a combo correctlly, your car will run better. Even if your car dosen't make more power, which is doubtful, things like fuel mileage, timing, detonation, and the all around way your car runs can be effected by diffrent quenches. The point is, just do it right the first time. If your talking to Brad, maybe you could get him to come in here and post his theory as to why he thinks you should use the stock gasket as opposed to the one that is the right height.
my pistons cam .010 out the hole and i went with the .045 cometic to set my quench at .035. brad knew all that which is one reason he didnt recommend a .054 gasket. my SCR is 12.02 so i needed a tight quench.
and
to inspector 
01-03-2005, 12:22 AM
#22
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I think these aluuminum blocks expand more than the traditional iron block that all our
quench data came from before.It is very possible we may have to run the quench tighter to allow for this.I've run them as tight as .029 on a iron block with good steel rods before and spun the motor to 8600 and not closed the top rind land.Any time you
can close the quench down you will make more power as the volume of mixture traped
in the quench band does not contribute to combustion.Reduce this volume and power goes up.In my experience quench does not begin to pay dividends untill it is under about .050-.045.Above that dimention combustion can occur in the quench area.
quench data came from before.It is very possible we may have to run the quench tighter to allow for this.I've run them as tight as .029 on a iron block with good steel rods before and spun the motor to 8600 and not closed the top rind land.Any time you
can close the quench down you will make more power as the volume of mixture traped
in the quench band does not contribute to combustion.Reduce this volume and power goes up.In my experience quench does not begin to pay dividends untill it is under about .050-.045.Above that dimention combustion can occur in the quench area.
01-03-2005, 12:25 AM
#23
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Originally Posted by z-ya
I think these aluuminum blocks expand more than the traditional iron block that all our quench data came from before.
01-03-2005, 12:37 AM
#24
Originally Posted by Grant B
You know, I've asked a number of engine builders if this was the case and I have not gotten an answer. I did the math on the expansion difference somewhere, where did I put that...
01-03-2005, 07:00 AM
#25
I always make a list of questions to ask when I'm on the phone. I'm looking at that list and this was one of the questions I asked Brad. His answer was to use the GM gasket.I will be speaking to Brad later this week and will ask him to explain why.
Seems to me that the higher the compression, the quench area would be more of a consideration, since it would help with detonation.
Seems to me that the higher the compression, the quench area would be more of a consideration, since it would help with detonation.
01-03-2005, 07:26 AM
#26
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It all depends on what heads you have also. AFR for exemple has a double quench area compared to GM castings.
Also keep in mind that when calculating quench, you'll have to use the COMPRESSED thickness (for those who do not know).
I went with .045 cometic with .007 out of hole for .038 quench.
These little things add up in power output, that is why I believe in balanced systems.
Doing so with LS6/918/tit ret/ valvetrain, portmatching my 241 castings to intake and exhaust primaries and a 224/220 Stealth II XE-R, + 98 octane fuel, I'm able to achieve 400+rwhp cam only on my A4. (something 99% of the poeple said I could never achieve with that cam and bolt ons)
Also keep in mind that when calculating quench, you'll have to use the COMPRESSED thickness (for those who do not know).
I went with .045 cometic with .007 out of hole for .038 quench.
These little things add up in power output, that is why I believe in balanced systems.
Doing so with LS6/918/tit ret/ valvetrain, portmatching my 241 castings to intake and exhaust primaries and a 224/220 Stealth II XE-R, + 98 octane fuel, I'm able to achieve 400+rwhp cam only on my A4. (something 99% of the poeple said I could never achieve with that cam and bolt ons)
01-15-2005, 03:32 AM
#28
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You can now get 3.90 bore .o42 compressed thickness gaskets from mr gasket for around $20.00 each.The part numbers are 5713g for the left side and 5714g for the right,these are in their ultraseal line .
01-15-2005, 06:30 AM
#29
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Originally Posted by Beast96Z
Well, there is no need to ask the application when you are talking about a gasket that is .064" thick, or even .054". I'm not even talking about bore size, I'm talking about thicness and setting a quench height. In a traditional motor you want .035-.040 between the deck of your head and the top of the piston at TDC. In this case, a .064 or .054 gasket will not get you the quench area you want. The only place that makes the proper gasket is Cometic at .045" or .040" depending on your piston out of hole height.
01-15-2005, 08:07 AM
#30
Finally got a chance to talk with Brad @ FFHP about my heads and asked him again about quench. While he doesn't think it makes THAT much difference, he agreed that if your looking for every last hp the 035 - 040 or less fiqure is what you need. He still said I'd be "fine" with the 054 stock gasket. Since I plan to do this only once I'm going to use either the new Mr Gasket 042 or the Cometic 045. I'd rather be "optimal" instead of "fine" but I'm sure that the overwhelming majority would settle for "fine" and that's probably why he doesn't make a big deal out of quench.
01-17-2005, 11:49 PM
#31
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well it's safer to be a bit large than a bit small,and since he is not doing the measuring
of the block in most cases he probably feels more comfortable going conservative.After all if a motor was damaged on his advice it would be a major liability,where as most people would not know they left a little on the table with a larger squish.Not worth the risk if you can't controll the variables.
of the block in most cases he probably feels more comfortable going conservative.After all if a motor was damaged on his advice it would be a major liability,where as most people would not know they left a little on the table with a larger squish.Not worth the risk if you can't controll the variables.
