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I have probably 6-8 sets of 7 layer “ls9” MLS gaskets. Some are the smaller 3.8” BTR LS9 equivalent 7 layer head gaskets.
I am looking at doing a high compression NA build on a budget with an SBE 5.3 motor. Already have the in-head fly cutters to trim piston valve reliefs as needed.
Question is… instead of buying “thin” head gaskets at $90 each from Cometic. (.027). I was wondering if I can simply take apart a few of these used “good”. MLS gaskets, spray them with copper spray. And make my own "thinner" HG.
I’m already milling the 706 heads down as far as possible. I don’t need .027 but I figured every little bit helps.
FWIW I’ve reused MLS LS9 head gaskets multiple times with no real issues on turbo setups. I only spray used gaskets. A new gasket has the proper water seals already and spraying stops heat transfer between the head/block. Not a huge deal for an NA setup, but not ideal with forced induction, which is what I usually work with.
I want to say Kurt Urban or some of the other well-known performance guys have broken down HG’s and made their own “custom thickness” gaskets. But I can’t find the threads anymore.
This is a low buck JY build, it’s the only reason I’m considering it.
I don't know how many layers are usually used in these gaskets, but I can see pulling one apart and removing one or more layers from the middle, leaving both sealing surfaces intact. ONLY thinking out loud here.... which occasionally gets me in trouble... LOL
Mill and fly cut rinse, repeat and then angle mill. Do whatever you got to do. Tell the machinist you want the valves so far down inside the Pistons you'll need to clearance the connecting rods. Do whatever you need to do to get 13-15:1 or more get after it son, but please Just use a stupid parts counter felpro head gasket and forget about it for the rest of your life. Your DCR calculated intake valve closure event, with the head flow, intake flow capability and your exhaust flow capacity, think about that stuff. getting that intake closed as early as possible while still carrying it out as far as you need it to without causing detonation under load at low revs. That's where you're going to get the power, rectangular ports make more power than cathedrals with less compression all the time It's not worth the bother, You can do this without the spaceship stuff. I'm not made of money and you aren't either This isn't the place to waste yours imo I'd hate to see you break it chasing 0.05 HP or whatever you're going to get until the first time it overheats when you know the stock quench is good enough for about a million pounds of boost right? Well, your build will last about a million miles if you don't worry about this kind of stuff, nitpick the cam profile and the tune not this, Just my two cents man
Appreciate the input! I’ve only worked with turbo setups in the past. Trying something new with this NA stuff and I’m not familiar with it.
The center of the 7 layer LS9 gasket is what appears to be a phenolic spacer. This is what I was thinking of removing. I have a dozen+ used ls9 and small bore BTR 7 layer gaskets. hanging on the wall. So I’d get HG’s to play with free. I was mainly looking for someone who has actually done this with success. I know I read about it in the past, but I was turbo then. So I wasn't concerned about higher compression.
I have an Individual Throttle Body intake that bolts individually to each head. So I’m Hoping intake fitment won’t be an issue.
I’ve read for every .006 you take off roughly 1cc. So .072 would remove roughly 12cc and give me a 50cc head on a 706. I’m told you can go .080 before modding the bolt holes. I can’t use rec port heads on a small bore motor, so stuck with these. I sold the 799’s for $450. And picked up these 706’s for $125. A 50cc chamber with a .030 HG *should* net around 13.2:1.
As silly as it sounds, I’m doing this for sound mainly. I could go much quicker for half the cost with a small turbo on a bone stock motor. But I’ve gone that route, many times! I want it to sound angry and some of the 13:1+ LS setups at our track sound plain nasty. Hoping the ITB’s will add to this. Will be in a 2400lb rx-7 with a manual trans, so don’t need to light the world on fire power wise. I do want it to sound like an exotic… or as close as one can get without a flat plane crank, lol! 180* exh. manifolds may be in the future as well. But I’d like to get it together and running first.
Last edited by Forcefed86; 11-29-2023 at 02:07 PM.
I think the post above mine (stock A4) contains a lot of truth. But I also think Atsma has come up with a possibility. The key to Gary's idea would be to get all of the layers (3?) EXACTLY in line with each other. Another key is keeping the outer edges, top and bottom layer, and using whatever number of layers you'd need to attain the desired thickness. That way you'd keep the sealing capability. If it was Kurt Urban who has done this, Kurt is one of the top engine guys in the country, and is very approachable. If he has done this, he'd be the first guy I'd ask. I think he is still running the crate engine program at Scoggin/Dickey. But for me, I'd much rather trust GM or Cometic. If I was younger, I probably would be willing to try to alter head gaskets. But as you get older, pulling a set of heads because I tried to save $100 isn't my idea of fun nowadays. Especially if it could've been avoided. Work SMART, not hard, comes to mind here......
I think the post above mine (stock A4) contains a lot of truth. But I also think Atsma has come up with a possibility. The key to Gary's idea would be to get all of the layers (3?) EXACTLY in line with each other. Another key is keeping the outer edges, top and bottom layer, and using whatever number of layers you'd need to attain the desired thickness. That way you'd keep the sealing capability. If it was Kurt Urban who has done this, Kurt is one of the top engine guys in the country, and is very approachable. If he has done this, he'd be the first guy I'd ask. I think he is still running the crate engine program at Scoggin/Dickey. But for me, I'd much rather trust GM or Cometic. If I was younger, I probably would be willing to try to alter head gaskets. But as you get older, pulling a set of heads because I tried to save $100 isn't my idea of fun nowadays. Especially if it could've been avoided. Work SMART, not hard, comes to mind here......
I hear ya. I'm 43 and don't feel like pulling motors due to HG seal issues either. I will say I've run a ton of turbo motors and I really don't think head sealing on NA LS motors is a big issue.
I mainly wanted to know the purpose of each layer. That way I know the order to put them on, and which layers are necessary VS unnecessary. I have a PM out to Kurt, he's helped me out in the past as well. But he's a busy fella.
Its basically $100 per gasket if I go with the .027 Cometics. The motor itself is about $500, so there in lies my issue. I'm throwing tons of money at the drivetrain, intake, EFI setup etc etc... So If I can save a little and learn something doing it. I'm all for that.
I don't think layer alignment would be an issue due to the dowel pins. The gasket layers would have to drop down over the dowels so they would align pretty much exactly as needed. But I don't know which layers are necessary vs unnecessary. In my old Turbo Buick days we used a single steel shim with sealer on both sides... So I'm sure i'm over complicating this... Mainly brain storming and looking for ideas and past experience.
You guys are the worst, now I'm looking at this stupid 02' 5.3L with worn out piston skirts My friend left at my house. I was going to respond again earlier but instead I sauntered into my junk pile like a zombie and drug out a pair of clean 706's and dumped them under the engine stand because you guys are buttheads. I want to be proven wrong here, so when you were shimming those Buick engines where you machining the deck of the block and the head surface as well or did it work with the stock unaltered components?
That's pretty neat, even cooler that the gaskets are reusable
What pistons are you using for the build ? I'll be looking for some used 4.8L pistons to throw in mine before I do anything else to it I've had good results with them before, just be careful pressing the old pins out
On a stock JY engine, the pistons are going going to be .004-.006 out of the hole. You need to use a deck bridge and find the EXACT measurement before you order gaskets. I can tell you that .028 quench has been tried in the past and it failed. Tony Mamo tried it actually…with a forged bottom end as well. So if your .005 out for instance, and you throw a .027 gasket at it, that leaves .026 quench. It will hit the head somewhere above 5k rpm. Rod stretch and production tolerances will show up and instantly put a few hundred tiny pieces of aluminum in the oil pan at high rpm.
I wouldn’t go any lower than .030. I kept mine at .035 simply because the heads are $5k and I don’t want to buy another set because of a failed experiment. Your not going to find any performance gains going from .035 to .025. I’m just trying to save you some work and money here.
…..edit…LOL…if piston is .005 out, with a .027 gasket, you’ll have .022 quench, not .026. Trying to type too fast I guess.
Last edited by Che70velle; 11-30-2023 at 05:55 PM.
Reason: My math is wonky…LOL
i ran 032 on an old 385" sbc back in the day and when i took the heads off the pistons were bare (no carbon) in the shape of the combustion chambers. im not sure id want to go much tighter. it was a forged bottom end, 4.040 bore.
as for the restacking of head gaskets, cant say its a good idea but i would 100% do it. i have never used a new gasket on a turbo ls motor of mine yet. one recently i did used head gaskets, used stock bolts impacted down, 16 psi and drove the car an easy 10k miles across numerous state lines.
That's for Cheapskates who rather Involve Risk Failure. Had Failure to a Friend's Money Build by a supposably Good Builder. Racing and Blowing Engines Up is already Risky Enough, why Increase the Risk? Especially when you have dumped Money into the Build. Just get you good Gaskets like Cosmetics. But I understand it's your Money, Blow It however you choose.
That's pretty neat, even cooler that the gaskets are reusable
What pistons are you using for the build ? I'll be looking for some used 4.8L pistons to throw in mine before I do anything else to it I've had good results with them before, just be careful pressing the old pins out
Its an older LC9. So it has the floating flat tops in it. I've seen the OEM flat tops fly cut .170 and survive.
On a stock JY engine, the pistons are going going to be .004-.006 out of the hole. You need to use a deck bridge and find the EXACT measurement before you order gaskets. I can tell you that .028 quench has been tried in the past and it failed. Tony Mamo tried it actually…with a forged bottom end as well. So if your .005 out for instance, and you throw a .027 gasket at it, that leaves .026 quench. It will hit the head somewhere above 5k rpm. Rod stretch and production tolerances will show up and instantly put a few hundred tiny pieces of aluminum in the oil pan at high rpm.
I wouldn’t go any lower than .030. I kept mine at .035 simply because the heads are $5k and I don’t want to buy another set because of a failed experiment. Your not going to find any performance gains going from .035 to .025. I’m just trying to save you some work and money here.
Appreciate the input. I don't' know what a ls9 gasket thickness would be with the phenolic removed. They are .055 untouched. I'll see if I can get a measurement on that specific layer.
Also find it hard to believe they sell .027 thickness gaskets if they would cause instant failures over 5k. In fact... I believe I ran a .027 gasket on a 4.8 many years back. I was looking for more compression because I ran 799 heads on it. And I buzzed that sucker to 7800 quite often. So I think there may be other factors at play there.
Last edited by Forcefed86; 11-30-2023 at 09:38 AM.
That's for Cheapskates who rather Involve Risk Failure. Had Failure to a Friend's Money Build by a supposably Good Builder. Racing and Blowing Engines Up is already Risky Enough, why Increase the Risk? Especially when you have dumped Money into the Build. Just get you good Gaskets like Cosmetics. But I understand it's your Money, Blow It however you choose.
These are the comments I love... And why I don't want to go down the beaten bandwagon path. Be your own builder! Make your own decisions based off facts and data, and learn something.
Too many simply pay others, telling themselves its the right path. I can say 80% of the time I've farmed something out to others... mistakes were made. Wanting to know what is possible and what each layer is for and using what you have instead if constantly buying new isn't "cheap" IMO, its smart. There's no reason to drop another $200 on gaskets when I have a wall full of them that *might* work perfectly fine. The *might* is what I'm researching.
Guarantee I won't blow an engine because I re-used a HG.
11-28-2023, 03:19 PM
Making your own thin “MLS” Head gasket. 
