NasbaGoat

Backround....
2004 GTO/243's/LFPE GT9 cam/MP112HH/10.75lbs boost
Pushing water into the oil, heads are at the machine shop to be checked for cracks and straightness....

Question....

In my reading i have determined that the LS9 head gasket is 4.1" bore 7 layer MLS gasket and the LS1/6 is a 3.91" 5 layer MLS gasket. I have also gathered that people think more layers/ purpose build gasket is better and that people have used them successfully.

What i havent found is an explanation as to why it is ok to use a gasket that has a much bigger bore than the cylinder and why it wont create problems for me.

Ferocity02

iTrader: (60)

Myself and many others have been using them on their 5.3 and 4.8 blocks which have an even smaller bore.

Slowhawk

iTrader: (12)

People use them, I see no reason too.

Our builds always get the correct bore size and the high hp cars get copper sprayed. No gasket problems- ever.

Twin turbo c5

Why? Because they work. They have proven there self again and again By me and many others. Use em.

Scoggin Dickey

iTrader: (34)

If you are running the proper bore size and your heads have the proper sized combustion chamber I will recommend the LS9 head gaskets for bang for the buck. If you want cheap head gaskets for a 5.3 use the GM MLS LS1 gasket set. It's cheaper than a pair of LS9 gaskets and they are sized properly for the application.

Do people use LS9 gaskets successfully on small bore setups? Sure they do. Does successful misuse of a part make it proper to continue to do so? No. I do not recommend an LS9 head gasket for use on a small bore like the 5.3 and I recommend that anyone installing heads does so with the properly sized head gasket for their combination.

trav-tech

iTrader: (1)

well put scoggin dickey. im running and have been running the standard 3 layer ls1 gaskets on my 5.3L making and holding 876rwhp and dont see the point in paying more for a gasket with the incorrect bore size when the normal gasket holds the pressure just fine. most guys will bend the stock gen 3 rods long before pushing water even with stock stretch bolts.

a-low

iTrader: (26)

I always wondered the same thing, large bore gasket on a small bore
with more layers just drops compression. But what the hell do i know.

stevieturbo

More layers has nothing to do with compression. Overall thickness is the same.

But any of the GM MLS gaskets work superbly, I'd always prefer to use the correct bore'd gasket for my engine unless there was no alternative.

68 SS

iTrader: (23)

The most important thing is the surface finish on the heads and block without that being right you will have issues.

stock48

iTrader: (17)

The extra layers allow the Ls9 gasket to hold seal when heads flex.

LS1NOVA

iTrader: (12)

$35 a pair LS1 MLS gaskets working well on my small bore. I agree with the others, I just dont like the gap.

Wicked69

LS9 head gaskets, just wipe the surface and have hit 25lbs of boost without pushing water. Short bursts. Recently 11.0 compression, 14lbs of boost, head gasket didn't go but ring land let go.

stock48

iTrader: (17)

I have pushed water past 20psi with the std 3 layer truck gaskets. Been up to 25 psi with ls9's S480, 6.0L with 317's and no water pushed. Combo went 6.03/117mph on 22 psi @ 4800lbs so it's pushing things a little lol .

TDMKR496

iTrader: (3)

Do you have a build thread for your truck??

badhombre

iTrader: (4)

I just had this same conversation with a friend. I ordered a set of LS1 MLS gaskets through Jegs. he told me I should return them and buy the ls9's. I have seen the ls1 gaskets holding up to plenty of abuse so far, so I think I will be good. especially in combination with studs

stock48

iTrader: (17)

No build thread I built truck back in 2006. Built the whole thing in a week and have made little upgrades, and down grades here and there. Not really much to it other than the turbo kit, engine swap, and upgraded transmission. Every thing else is stock 2003 truck down to the factory intake, tb, etc lol. There are some older vids on youtube under stock48.

Chicago TDP

iTrader: (3)

Doesnt it all boil down to the fact that the GM LS9 is a FACTORY supercharged engine, making almost 650 HP out of the box?

The fact that a OEM made a gasket that will hold up to boost on a factory motor might indicate that it is the "premium" choice to hold boost.

I see it as if GM engineered/built a gasket for a high HP boosted motors (so they dont loose their *** on warranty claims), then I will bolt a set under every boosted motor I put together.

Scoggin Dickey

iTrader: (34)

They also built said gasket for a 4.065 bore engine. There is a reason head gaskets are offered in varying bores. The fact that they engineered something to work properly on an LS9 doesn't mean it's the best for a 5.3 just because the 5.3 is now boosted. There are still big differences between the two engines.

An LS9 head gasket on a 5.3 leaves you with a .051" gap between the block and the head that is .095" wide all the way around the bore (compared to a properly sized 3.910 bore gasket). This is simply not ideal regardless of whether it works or not.

The GM 3.910 bore MLS gaskets are good for decent boost and power. When exceeding what they are good for it's best to step up to a properly sized Cometic.

1BADAZZSS

iTrader: (23)

I know MaxMitchell and skinnies have been running the ls9 gaskets on small bore motors (l33s) and have no issues. I lifted a head last year on a jy 6l with mls gaskets. Changed to the ls9s and no issues since!

MonmouthCtyLS7

iTrader: (6)

I hear both ends but theres a reason tons of guys run 9's on boosted motors...believe the thickness effect out weighs the bore differences.