Should I go with gaskets on my exhaust manifolds?

[Michael L.]

guys,

I'm about to bolt on my exhaust manifolds and have read in the judging guide that there were no exhaust gaskets originally from the factory on my 69 sb. Should I assemble again without gaskets, or should I put gaskets on there? What's the likelihood of a leak if I go no gaskets? Thanks.

Mike

[Donald H.]

Re: Should I go with gaskets on my exhaust manifolds?

If the mating surfaces are true then you should not have any leaks. I did not use gaskets on my 60 or 66. But I did make sure the manifold surfaces were flat and true. I used the top of my table saw, which is a machine flat surface and sandpaper.

but if you feel better using the gaskets, it's your car. If you have it judge, you'll probably take a small here.

[James N.]

Re: Should I go with gaskets on my exhaust manifolds?

No need for gaskets. There was a great article is a recent Restorer about hand finishing manifolds. Don't know the issue off-hand. Maybe someone else can chime in.

[Joe C.]

Re: Should I go with gaskets on my exhaust manifolds?

guys,

I'm about to bolt on my exhaust manifolds and have read in the judging guide that there were no exhaust gaskets originally from the factory on my 69 sb. Should I assemble again without gaskets, or should I put gaskets on there? What's the likelihood of a leak if I go no gaskets? Thanks.

Mike

If you don't use gaskets there is metal-to-metal contact so when you torque the bolts, they will stay torqued. If you use gaskets, they are soft and will continually compress which means the bolts will not maintain torque and will eventually loosen if you don't keep after them.

Use a thin film of red RTV on the flanges and torque the bolts to spec. Any small leak(s) will eventually carbon-up and seal in fairly short order. There is some possibility of leaks unless your manifolds are perfectly flat, but once torqued, most of any warpage will be pulled into place.

[Joe L.]

Re: Should I go with gaskets on my exhaust manifolds?

guys,

I'm about to bolt on my exhaust manifolds and have read in the judging guide that there were no exhaust gaskets originally from the factory on my 69 sb. Should I assemble again without gaskets, or should I put gaskets on there? What's the likelihood of a leak if I go no gaskets? Thanks.

Mike

Mike-----


I agree with the others; no gaskets were originally used for the vast majority of Corvette applications (there were a few exceptions, though). If your manifolds are flat and true, no gaskets are needed now. The only reason that gaskets are supplied in many engine rebuild gasket kits is that, sometimes, exhaust manifolds in long service develop some degree of warping with ensuing exhaust leaks. So, the gaskets represent a "preventative measure". They don't harm anything if installed and they might do some good. The VAST, VAST majority of folks that use them as part of an engine rebuild do not care, at all, about originality and are all for heading off possible problems.

You should check the manifolds for being straight and true using a precision straight edge or other method as Don suggests. If they are off, then have a machine shop resurface them.

One thing that doesn't apply in your case but I'll mention here anyway: in the case of aluminum heads used with cast iron exhaust manifolds, I like to use gaskets. GM didn't do this "back in the day" (with the VERY few engines equipped with aluminum heads), but I like to. I don't use those "waffle" type gaskets supplied in rebuild kits, though. I use multi-layer steel type gaskets.

[Michael J.]

Re: Should I go with gaskets on my exhaust manifolds?

I totally agree with Joe if you want a dependable driving car with no leaks, always use the gaskets. If you lose some points at judging, big deal, well worth it and you can pick up points other places that are less important than having leaky exhaust manifolds on a car you want to drive frequently, my dos centavos.

[Patrick H.]

Re: Should I go with gaskets on my exhaust manifolds?

I totally agree with Joe if you want a dependable driving car with no leaks, always use the gaskets. If you lose some points at judging, big deal, well worth it and you can pick up points other places that are less important than having leaky exhaust manifolds on a car you want to drive frequently, my dos centavos.

I'll completely disagree.

I installed gaskets several times on my 71 after I rebuilt the engine (and trued the manifolds) back in 1996. I had to replace them almost yearly, as they ALWAYS burned out, no matter what the brand.

I got tired of it, resurfaced them again (just to be sure), installed them and had zero issues. Every car I have worked on since I do the same, and they don't leak.

So, I would suggest having your machine shop true the exhaust manifolds, and avoiding gaskets at all costs if you want to avoid headaches.

[Michael J.]

Re: Should I go with gaskets on my exhaust manifolds?

I have never had an exhaust manifold leak on any car engine I have ever had rebuilt with gaskets over the last 50 years. I'm amazed at reports of problems.

[Christopher R.]

Re: Should I go with gaskets on my exhaust manifolds?

You shouldn't need gaskets. If it's make you feel better, put some Permatex High Temperature sealant in there.

You might consider using anti-seize on the bolts.

[Jim D.]

Re: Should I go with gaskets on my exhaust manifolds?

I have never had an exhaust manifold leak on any car engine I have ever had rebuilt with gaskets over the last 50 years. I'm amazed at reports of problems.

I agree. I've always used gaskets and never had a leak or have the bolts loosen on any car. In fact, the ones on my 1960 were installed in 1986 when I completed the body-off restoration and still no leaks.

[Patrick H.]

Re: Should I go with gaskets on my exhaust manifolds?

Antiseize (copper type) on the bolts, mostly because they rust over time.
Torque in correct sequence and torque to spec.
Use the french locks!
I often but a TINY bit of anti-seize around the holes in the french locks, or under the head of the bolt, as the french locks seem to love to twist.

You're done...I'd say forever, but we never seem to leave these cars alone.

[Jeffrey S.]

Re: Should I go with gaskets on my exhaust manifolds?

When I had the engine in my '69 SB rebuilt I taped some sandpaper to the bed of my jointer in the wood shop. I ran the mating surfaces of the exhaust manifolds back and forth until the entire surface was shiny. Bolted them on and no leaks. Just my 2 cents.
Jeff

[Michael L.]

Re: Should I go with gaskets on my exhaust manifolds?

Really helpful input guys thanks. Think I'll go with getting the manifolds resurfaced as needed and not use any gaskets.

[Joe L.]

Re: Should I go with gaskets on my exhaust manifolds?

I totally agree with Joe if you want a dependable driving car with no leaks, always use the gaskets. If you lose some points at judging, big deal, well worth it and you can pick up points other places that are less important than having leaky exhaust manifolds on a car you want to drive frequently, my dos centavos.

Michael-----


I think that perhaps you misunderstood me. I was not endorsing the use of gaskets. The best plan is to ensure the manifold surfaces are straight-and-true and installing the manifolds without gaskets. I do like to use gaskets when installing cast iron manifolds on aluminum heads but, in that case, I use only multi-layer steel gaskets.

[Douglas L.]

Re: Should I go with gaskets on my exhaust manifolds?

Just to add, if using gaskets, like Joe said, avoid the waffle type gaskets that are typically included in rebuild kits. They are nearly guaranteed to blow out unless the surfaces are super flat and retorqued multiple times.


I've played around alot with different gasket types even resorting to making my own out of copper on a CNC laser cutter(mostly on hard to seal engines like Oldsmobile and Cadillac V8s) and have had the best luck with stainless steel shim type and solid material types from companies like Byson gaskets.


I used Byson gaskets on my 68 L36 car and while I did lose a couple of points during judging I felt it was worth it to not have to worry about leaks in the future. Doug