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My builder told me it was best to go with Ls9 head gaskets for my Na motor. However, for some reason it doesnt seem right to use a gasket that is .100 larger than the cyclinder bore.
Do these gaskets reduce compression in any way by adding .100 more surface area between the head and block? It seems like that is a bit of wasted space....but something is going on in there right?
Do they hold up better than the standard mls gasket?
That .100 absolutely makes a difference. Not huge, but almost a tenth of a point on a stock LS2. You can do the calcs with Cam Motion's calculator available here; I play with it all the time:
Not enough of a difference to really notice but as Mercier said it will effect your compression a small amount. As far as the bore diameter difference goes, you wouldnt have a problem using the LS9s. But Im curious as to why the builder would recommend the LS9 gaskets for an NA build. IMO, Id just run the stock ls2/ls3 gaskets unless you plan to throw a power adder on in the future. People usually run the LS9 gaskets in boosted applications because they have more layers, but NA I dont see why that would make much of a difference.
Im going to go with mls ls2 head gaskets. I dont want to lose any compression at all. Im shooting for at least 11.1 by doing a slight mill because im running a 235/243 111+2 lsa cam.
The builders reasoning was...if they can handle boost, they can handle all the stress an Na motor would put them through...and for a few bucks more..why not.
However, i dont want to lose any compression at all, and i want to gain one tenth of a point.
I dont want to run thinner cometics either. Can anyone tell me how much needs to be milled for the ls2 to reach 11.0-1 compression up from the 10.9?
You could mill them .010" and get between 11.0-11.1:1 using a factory gasket and if nothing else inside the shortblock has changed (piston, rod length, stroke, deck height, etc.)
General rule of thumb is .006" mill per cc removed from the combustion chamber. So plug a chamber volume in that calculator that gets you to the compression you want and that will tell you how much to mill. .010 is probably a good place to be but if you don't mind running premium fuel, with a good tune you should be able to get away with a little higher than 11:1 and make more power.
Chasing a .1 of compression is a waste of time. Your not going to notice it.
Your application doesn't need LS9 gaskets, but they won't hurt you enough to worry about it.
Chasing a .1 of compression is a waste of time. Your not going to notice it.
Your application doesn't need LS9 gaskets, but they won't hurt you enough to worry about it.
I don't disagree with your logic in the context you set, but if the OP hadn't bought gaskets(apparently hadn't), why not go with the cheaper gasket that more closely matches the bore size and get that .08 or so compression and the $8 in your pocket?
The NHRA S/S Comp class rules with respect to Head Gasket and Squish.
1. LS-9 GM gasket @ .051" size.
2. The piston deck @ +.015".
We agree that the GM LS-2 is .041" with my tighter hand finding .038", a more compressed measurement than most.
THE FIRST QUESTION to be asked, "What is your deck height ?"
Lance
If the LS2 gasket is truly .041" thickness, then more is to be gained(or lost if that's what you had before) than just the .08 when compared to a .051" gasket.
You say we agree on the measurement. Please provide evidence of this? I do in fact have a used LS2 gasket set on the shelf at the shop but it's cold and across town so I'm not as motivated to go get it.
I'm not doubting you and truly interested to see the evidence. I am tired of seeing all of the sometimes wildly varying specs listed by vendors for GM/GMPP MLS gaskets. We shouldn't have to buy head gaskets by matter of opinion!
I used to treat the [insert big auto mfg name here] racing parts catalog as the definitive reference but I still find errors there sometimes, too.
Edit: I thought only the Cometics and Fel-Pros were that short, being .040" and .041" respectively. I am running the latter on a stock-ish bottom end LS2 build now to get to about .035 quench cold. Might be a little tighter than that until it warms up and things spread apart; my redneck decking operation has my deck clearance as high as .0065" I think.
Using a calculator, with a 10.9:1 engine with factory LS2 specs(4" bore, 3.622 stroke, 6.098 rod length , +.005 deck clearance cold, 4.100" gasket bore and .055" gasket(I may be wrong but THOUGHT this was right):
Removed .010 form the gasket and gained .29 SCR. That's not insignificant. Perhaps not worth it to some to chase, but if free because you haven't bought the parts, why not?
The above, of course, hinges on actual compressed thickness of LS2 head gasket. If it really is .041 or less, then what else is wrong in my assumptions that gets us down to 10.9:1 advertised factory SCR? I wouldn't be surprised if it was a little higher than advertised--it would explain how strong the LS2 is for what it is--but 3 tenths seems like a lot to be off.
PS - I forgot I had to grab some springs I promised to someone in the classifieds..so here is a used LS2 gasket. I had washed it and dried for measuring PTV before I bought new gaskets so I think pretty accurate read.
This is FACTORY LS2 gaskets (2007, 58x) and the GMPP "LS2" gaskets very well could measure different. This was holding them real tight.
Yes, you are correct, the GM OEM LS-2 is .051" compressed.
I stand corrected !
I should give a part number in the future.
My mistake is caused by my common Fel-Pro choice, the 1041 gasket AND not being specific.
Lance
All good. I'm a 1041 fan here as well. Just put a set on.
So OP, ask your machine shop "how far out of the hole" you are. Also known as your deck clearance. If it is +.005 or less, the Fel-Pro 1041 will get you all quenched up AND get you over 11:1..that is, unless you have some good-sized valve reliefs and you may be at 11:1. If you are - or "in the hole" you may want to mill and gasket.
My motor is at a shop that mainly works on ls engines, not a machine shop unfortunately or i would have them check my deck heigth.
I just want to know if anyone has ever used a 235/243 111+2 or similar size and done a slight mill on their heads without flycutting..........or am i just wasting my time for negligible gains by going .010 mill?
Or should i pay a couple hundred extra and flycut the pistons and mill them .020-.030? Would i see a huge power increase and throttle response? I dont mind running 93 gas full time. On my last build my car would detonate on 87 or 89 fuel anyway.
That cam isnt too far off from the polluter V2 im running and theres no way Id run a thinner gasket or mill the heads with the V2. Id say if you want to mill or run a thinner gasket have the engine assembler measure your ptv clearance and go from there. But Id say its safe to say you will most likely have to fly cut.
There is a method I use to measure an "open" block for the deck.
The measurement is taken from the Main Saddle to the Top of Block.
The tool I created to make this easy was a piece of 2.5" Heavy Wall tubing that was cut to length allowing it to fit between ONLY two mains.
That measured distance would need to have a measurement INCREASE of 1/2 the Main Housing Bore.
I have a question for Mercier : Would you be acquainted with Richard Wall, "Wall to Wall Racing" a Gator Farmer in your area ?
He installed my ECU-882C onto his LS powered "working" boat.
The boat operator called in at 11:00 am stating that the fuel gauge was not reading correctly.
Richard then called my shop to ask how to fix that gauge problem.
The operator returned to the farm, at noon, to "unload" the found eggs AND to refill the normally EMPTY fuel tank.
Richard then called me to state I also "broke" his fuel tank as it could no longer fit the normal amount of fuel, only about 1/2 that amount.
The next day I received an order from him for TWO more of my LS-ECUs
Lance, BTW he sent me a "gator" wallet for Christmas that year.
12-10-2016, 08:23 PM
Ls9 head gasket vs Ls2 head gasket 
