Exhaust manifolds - gasket / no gasket?

[brrian]

I'm almost ready to install my exhaust manifolds. It's trivial, but I hate seeing the gasket between the manifolds & heads. The factory didn't use gaskets but that would've been two fresh, new surfaces. But even on a rebuild, it seems like many people use gaskets & some don't. What do you all think? Some use no gaskets & just a bead of the high temp copper silicone, & I kind of like that but would like opinions first. Thanks...

 

[69hurstolds]

Depends. If the surfaces are completely flat, it should work fine. If not, use the gaskets if you're not removing the heads from the engine. The heads and manifolds were milled flat during manufacturing/assembly at the factory so you won't have any issues there, but after time, those same surfaces may not stay that way. If simply replacing the manifolds, it'd be too much of a hassle to ensure the head mating surfaces were flat, like removing the heads, etc., so a gasket would be fine to use.

Simply using an RTV filler compound would only be recommended if you had both sides checked/milled flat and had maybe a pit or two needing filling. I wouldn't trust it to be used as an overall gasket maker on the exhaust.

If you ran headers you ALWAYS will see gaskets. Nobody complains about them. Oldsmobile V8 is pretty cool because even though many use gaskets, you can hardly see them.

 

[buick7332]

I'm almost ready to install my exhaust manifolds. It's trivial, but I hate seeing the gasket between the manifolds & heads. The factory didn't use gaskets but that would've been two fresh, new surfaces. But even on a rebuild, it seems like many people use gaskets & some don't. What do you all think? Some use no gaskets & just a bead of the high temp copper silicone, & I kind of like that but would like opinions first. Thanks...
I've had my GS 350 for 25 years and have always used fel pro gaskets without any sealant and always had good luck. I take them off every so often to repaint them. I would recommend new grade 8 bolts ( I bought mine at Home Depot) and high temp anti sieze compound.

 

[Sweet_Johnny]

Try it with just the liquid copper and if it leaks you'll do the job twice, if it doesn't you'll have achieved the look you want. How bad do you want that look? I think 69hurstolds makes valid points, however I'm inclined to believe that a rasp and a steady hand could alleviate any potential problem areas if it's even necessary.

I'd give them all a few very light passes with a quality rasp like an old Nicholson or Pferd and go for it, but I'm a risk taker. If you do go at it with a rasp then you run the risk of all the surfaces being flat yet not flush with each other.

Edit: GOOD drill presses can be used to do LIGHT milling procedures such as surfacing.

 

[Bonnewagon]

I mainly do Pontiac V-8's so I always use a fresh steel gasket. It is designed to be crushed and make a seal but can only be used once. This is a Buick, right? The last time I had one I didn't use a gasket and regretted that. This kind of set is really nice and you won't even know it's there. But you may know it's NOT there.

 

[abbey castro]

I'm almost ready to install my exhaust manifolds. It's trivial, but I hate seeing the gasket between the manifolds & heads. The factory didn't use gaskets but that would've been two fresh, new surfaces. But even on a rebuild, it seems like many people use gaskets & some don't. What do you all think? Some use no gaskets & just a bead of the high temp copper silicone, & I kind of like that but would like opinions first. Thanks...

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I guess the silicone oozing out looks better than a gasket? Use the gaskets to ensure a good mating surface, or if you don't then time will tell if you begin to see the stain of a leak. Let us know which way you go.

 

[brrian]

I guess the silicone oozing out looks better than a gasket?

If it oozed out I'd clean it up. I wouldn't leave the gaskets out if it was clearly the right thing to do, but from what I've seen, it's not. Some insist they're necessary, some say they're not. Some say they can blow out / burn out over time. Those that don't use them - some use a sealant, some don't. I'll just order a set & probably put them in because this is my first swap & I don't have the experience / guts to go without them right now.

 

[bracketchev1221]

Yes the small individual gaskets are the manifold ones.

 

[SS_Malibu]

I've never heard of not using exhaust gaskets. To me, not using them would incur leaking. I vote for using gaskets every time.

 

[-dw-]

If you ran headers you ALWAYS will see gaskets. Nobody complains about them. Oldsmobile V8 is pretty cool because even though many use gaskets, you can hardly see them.

5 sets of gbody bigblock olds I built. After the first set the rest were ground flat and reg rtv used. Heads were remachined on the exhaust side to. Had an extra head on the bench I would check to make the headers bolted on flat.