BB

iTrader: (7)

Is the price difference in the GM MLS verus Cometic due to the choices Cometic gives you in thickness and bore? Is there anything else or any other reason to choose Cometic over the GM MLS?

I will have a 3.905 bore. Will I need the Cometic or can I go with the GM MLS?

Beast96Z

iTrader: (21)

The GM MLS are way to thick. Unfortuantlly, for the stock bore guys, we don't have any other choices than cometic. Although the are great gaskets, they just cost to much. But, there is no other way to set a correct quench, so sometimes you have to bite the bullet.

BB

iTrader: (7)

What about the bore size. Will the GM work on a 3.905 bore?

Inspector12

iTrader: (29)

Yes just buy the ones for a 6.0 not a 5.7.

Beast96Z

iTrader: (21)

Why would you even want the GM gasket? Unless price is of you highest concern, it won't be the proper gasket.

Inspector12

iTrader: (29)

And why would it not be the proper gasket because it is a 3.905 vs a 4.0? That will not make a difference. Its done all the time.

99Fbody99

The GM MLS gaskets are not only the best, but also the cheapest.

Also, stating arbitrarilly they are too thick without asking the application is silly.

And, to boot..The stock 5.7GM MLS gaskest from summit..a woppin $25 a pair..hard to beat..and they will fit a 3.905 all day long. If your using 6.0L heads then go with the 6.0L 4" bore gaskets.

Dave

Inspector12

iTrader: (29)

Thanks Dave I couldn't remember if the 5.7 would work for sure on a 3.905.

BB

iTrader: (7)

Is the GM reusable? If it is not then that would negate the price advantange over time.

Until I get all the parts and get it together I won't know what I will need for thickness. I am hoping I can get away with GM gaskets.

Beast96Z

iTrader: (21)

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.

AFTICA

iTrader: (8)

Assuming most of our pistons are out of the bore by .008;

GM .054 - .008 = .046

Cometic .045 - .008 = .037

I'm told .040 is ideal for our motors with non forged parts. and .035 is too close. So will .006 make THAT much difference in power and/or detonation?
If it's not drastic wouldn't it be better to use the much cheaper GM gaskets and have the .006 as a safety margin?

BB

iTrader: (7)

Good question Aftica.

Beast96Z

iTrader: (21)

.035" isn't to close. Anything below that is getting to close. Some people actually prefer .032-.033 on stock short blocks, but that IMO is pushing it. .035-.040 is ideal for these motors, but .035 is going to provide more power than .040. You have that range because not every motor has the same deck height. So, when you buy a gasket, you try to get it within that margin. If cost is your major concern, then get the GM MLS. If your more worried about your motor being set-up to be efficent, then spend the extra $. Contact some of our sponsors. I found some willing to sell the Cometics for $52 a piece.

jrp

iTrader: (16)

i dont remember how much i paid for my cometics but in the grand scheme of things it wasnt that much.

the same people who try to save a few bucks on gaskets are the same people who when they dont put down the same numbers as one who did to set there quench right among other things with essentially the "same combo"

TAQuickness

iTrader: (28)

Beast and JRP seem to be onto something here. If you guys don't mind, would you share your knowledge of the effects of AFTICA's numbers

[QUOTE=AFTICA]
GM .054 - .008 = .046

Cometic .045 - .008 = .037
QUOTE]


Specifically, what's happening in the additional 9 thousands of an inch that skews the HP & TQ numbers?

Beast96Z

iTrader: (21)

Quench accelerates turbulence and further concentrates the remaining mixture in the combustion chamber, while leaving a small margin for carbon build up. Basically you are trying to direct your burn pattern to the exaust valve and not setting a proper quench further reduces your chances of a complete burn. That's your diffrence between optimum and .009 out. The further out you are, the less optimium burn you have.

leaftye

The Ignition Timing thread has some information about quench and what it does to timing.

AFTICA

iTrader: (8)

Based on my conversations with Brad at FFHP who recommends using the gaskets he ships with his heads (GM) .054, I was led to believe the difference (.009) meant nothing to HP and was getting too close for comfort. The only difference was the slight increase in compression...maybe 1 hp.

I will do whatever is best regardless of cost when I do my heads but after talking with Brad, I'm not sure what actually is best.

Again, what does the .009 buy you in hp?

Beast96Z

iTrader: (21)

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.

Inspector12

iTrader: (29)

I agree with JRP's statement some what on all peoples numbers not being the same as the next guy, but a lot of that happens from the factory too. So I think some of it is the luck of the draw on the stock bottom end cars. They say you loose 1% of total hp for every point of compression lower. It is just a gestimation. 100hp you would loose 1hp etc...I know there are more things to play into this as tunning etc. If he was building a complete race car this might make a real difference, but I don't think that is the case so the differences will be never seen.LOL! Good discussion though.I liked everyones imput.