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Need advice.

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Hey all,

Well after procrastinating for 6 months it was time for the replacement of the gasket between the intake and exhaust manifolds on the old 65 chevy 292.

As soon as the parts of the manifold were separated it was obvious there was a problem. The mating surfaces between the intake and exhaust manifolds are really pitted from rust. The intake side isn't that badly pitted and most likely will seal, but the intake side is questionable. Both have been filed in an effort to regain a flat surface. Of course the studs on the exhaust side are frozen in place making any kind of home resurfacing difficult, and it really is not worth having it resurfaced.

Anyone Know of a sealer that will hold up on the less than perfect sealing surfaces between the intake and exhaust manifolds?

And, is there anyway of replacing the heat riser? Is the heat riser even necessary in a warm climate?

Thanks for any advise in advance.

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Benefits of AACA Membership.

While I can't proffer advice on the sealant question, I can tell you that NO, a heat riser is not critical/mandatory in a warm climate. It's purpose was to allow the engine to warm faster in a cold climate by diverting the exhaust. Once the engine warmed, the valve opened and the exhaust exited normally out the tailpipe.

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I just went through a manifold change out on my 48 Fleetmaster with a 216 in it. The replacement manifolds I got came from a local junk yard, and, the sealing surfaces were pitted with rust. I took a Dremel tool with a sanding drum and lightly sanded the sealing areas areas that mated to the head, and, where the manifolds bolt together in the center. I then cleaned all the surfaces that had to seal really well with solvent. Next - I put two coats of spray on copper gasket sealer on all the sealing surfaces, and, a couple of coats on the manifold gaskets as well. I used a set from Felpro that were pretty thick. Put her back together, and, so far, no intake or exhaust leaks.

Regards:

Oldengineer

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Thanks for the ideas!

After cleaning it all up, the surfaces looked pretty good. I did use a little Permatex high temp RTV ( the orange stuff ) between the two maniflods just to be sure.

Well, as soon as it started, I could hear a small leak. :eek: Of course, this just will not do. So... the next step is removing the manifold for another check of the sealing area.

I'm just not sure it isn't that heat riser shaft leaking. The squish between the intake and exhaust manifolds really looked good. I find it hard to believe it would have leaked as soon as the engine was started. Maybe a little later, but not right off the bat.

Anyway, That's where it stands, the manifold has to come off, again!

Thank you once again for the ideas . I'll report my final fix, if I ever find one. :D

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The manifold gasket set I used included a rectangular gasket to go between the 2 manifolds. Some of the sets don't include this gasket - it must be purchased extra. When I put mine on - I buttered up the mating sufaces between manifolds and the gasket with the copper spray. I do have a small leak around the heat riser shaft, but, I'm not worried about it. Sounds like your set didn't include this gasket. The replacement exhaust manifold I put on has a functional heat riser. I've got it wired in the position so that it doesn't try to heat the carb. It's purpose is to prevent carb icing and enhance fuel vaporization in cold weather, and, I'm not going to drive this thing in Winter weather anyway. My old manifold had no heat riser, and, my car was hard to start when it was hot. I think the absence of the deflector paddle inside the exhaust manifold made the carb run hotter than normal, and, boiled off the fuel in the carb bowl. After I installed the manifolds, I ran the engine for a good half hour, temp guage was up to 180, and, I could put my hand on the intake manifold under the carb and it was lukewarm.

Regards:

Oldengineer

48 Chevy Fleetmaster Town Sedan

Edited by Oldengineer (see edit history)

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Hello once again,

Well... it turns out that one of the exhaust ports was leaking at the head. The gasket had a small burr on the mating surface and some black where the leak was, so after double checking the surfaces, and removing the nick in the gasket, it was reassembled again.

I'll be darned if it wasn't still leaking! WHAT THE? :confused: Off came the manifold! Now I'm on a mission!

The mating surfaces were perfect, pristine, show room clean. There was no reason found that explained the leak. So... the seal between the 2 manifolds became the suspected culprit.

The manifolds were split apart, and darn it, the seal was holding just fine. Go figure, uneven rusted surface seals, clean flat surface doesn't.

Oh yeah, there were 2 new gaskets that went between the 2 manifolds included in the kit. It wasn't just put together with sealant as the only form of gasket.

One of the gaskets was solid and covered the complete opening, the other just sealed the outer rim. The instructions stated that the solid one was for propane use. I can't imagine why the solid one couldn't be used when gasoline is the fuel. If anything, I'd think it would help keep the base of the carburetor cooler.

Anyway, a new coat of sealer was applied and the 2 manifolds were married once again. (may they live happily ever after)

Not wanting to risk a 4Th encounter with this leak, a small amount of sealer was used on the 2 inner most exhaust manifold ports before mating the manifold to the head. WA La! Success! No more leaks! :D Of course the quiet turned up more problem noises from deep inside the engine. :eek:

I thank one and all for the ideas.

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