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straight 8 exhaust manifold gasket leak[47super]


sledheader 48381

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I have replaced my exhaust manifold gasket three times in the last four years and am about to do it for a fourth time, five years ago I bought a new manifold from Bob's, I had it machined to match the intake and installed it with a standard gasket set I also used the 4 pilot rings, after a year it began to leak so again I replaced it this time with a copper clad gasket from Bob"s, year later leaking, did it again with the same results. The gasket seems to wrinkle up between the exhast and intake and start leaking.

I must be doing something wrong, any help will be appreciated.

Thanks Don

47 Model 56C

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Make sure you torque the manifold to 25-30 ft. lbs. cold, starting from the inside and alternating bolts until you tighten the outside ones, like you would a head (at least that's how I do it). Drive it for a week, then retorque them cold...I check mine every few months just to be safe.

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I also do the same and I use a mix of graphite and oil on

the copper clad gaskets. make a slurry with graphite and a little oil and coat both side of the gasket befoe installing.

This allows the manifolds to slide on the head easier.

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Hi Sledheader,

My '50 Model 52, 263 was doing the same thing including the copper gaskets wrinkling up between ports. I torqued them as above several times but they eventually wrinkled over 3/8" partially blocking #7 exhaust. Then I re-read the Buick repair manual several times and it said there are no gaskets on the exhaust manifold. I also have the 1950 Buick Service Bulletin and it says there are no gaskets on the exhaust manifold. Both say to use a mixture of graphite and oil, bolt it right to the head and follow torque instructions. In my case I cut out the intake portions of the non-copper multiple gasket and used those on the intake only. The mounting to the preheater section is adjustable so the intake & exhaust manifolds can seal to slightly separate levels on the head. I have seen an old set of 1940 replacement exhaust gaskets and they were 8 individual rings with inside ridges to hold them on the manifold as you install. I don't think that long manifold was ever supposed to share a common gasket with the intake even though they are sold that way. They just move around at different rates causing the wrinkling. Those little saddles on mine under the mounting bolts have 1/16" clear marks on the insides so that manifold does expand & contract quite a bit. Hope this helps. My dad had a '50 Super for 7 years and I don't remember him ever doing anything to the manifolds.

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  • 2 years later...

Well the 1940 shop manual indicates both intake and exhaust gaskets. I have been told ,however, not to use anything on the gaskets? I assumde that the graphite and oil mix helps the gaskets to last longer? I just bought the expensive copper set and don't want to keep doing this!

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I stand corrected! Upon further reading my manual the factory did not use exhaust manifold gaskets, rather a "special compound". Intake manifold gaskest were individual as well. So why do gasket makers use a 3 piece design for both intake and exhaust? I am now more preplexed on what to do now!

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They were thin metal rings that appear on ebay every now & then it took 4 of them plus there were 4 rings that fit into the manifold grafite compound would hold the rings in place while installing the manifold. That is probably the main reason that the manifolds cracked using gaskets,mechanics would do a valve job and not replace the rings there was a little offset between the 2 manifolds. Another thing that is not done to prevent cracking is to separate the heat riser box from the manifold install intake & exhaust = fallow the torque proceedure = then install the heat riser.

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I got tired of the leak on my '56, so under the advisement of a friend I took them out all together with nothing in-between. If there is any gap, it will soon fill with carbon, ie, they will become self sealing in very short order! Make sure your two surfaces are smooth, tighten them to spec, shut the hood, then don't think about it any more:D

It shouldn't matter on the configuration either, yes, mine is a V8, but my friends cars are 1930 Pierce Arrow, and 1939 Chrysler Imperial.

Anyway, just my two cents,

Jaybird

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I had similar frustrations on a '50 Super. I blew out three gaskets trying to figure this out. Problem was finally solved by having the exhaust manifold resurfaced on a mill. Turns out over the years of heating and cooling, the manifold warped. After a proper resurfacing, no further leaks.

The only trick was to find a machine shop with a mill table long enough to cut the manuifold from end to end in a single pass.

It is frustrating, I know, but this solved my problem permanently.

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  • 1 year later...
I also do the same and I use a mix of graphite and oil on

the copper clad gaskets. make a slurry with graphite and a little oil and coat both side of the gasket befoe installing.

This allows the manifolds to slide on the head easier.

I just ordered gaskets, but can't find copper clad or anything more advanced than standard gaskets. Anyone have a source?

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I believe the previous owner of my car had this same issue, only the manifolds wouldnt just leak at the gasket they would crack. I found an old exhaust in the trunk that was 3 pieces and on the 51 its really a one piece. The current manifold on it has a crack and a repair, still leaks... I found one on the net and will take it to a machine shop to be planed flat and will try the no gasket as stated in a few above posts.

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The reason Buick did not use exhaust manifold gaskets was for better heat transfer from the head to the manifold. Nailhead V8s did not use manifold gaskets either.

This kept the heads cooler.

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I had also replaced the exhaust manifold on my '40 with a new set from Bob's. A few years later and I got a leak near the back of the motor. While it lasted a few years, considering that the car is not a daily driver, I felt it should have lasted longer. I replaced the gasket with new copper gaskets and it is fine. I recently talked to and old mechanic who told me this is a common problem that is caused by the engine timing being off and therefore that rear cylinder runs hotter than the others, thus causing the leak. I have not checked the timing yet, but I thought I'd pass this along to help others, and to see what everyone else thought of this theory.

Phil

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51 manual says, new pilot ring recess and gasket between body and manifold, leave attaching nuts snug but not tight,

coat surfaces with graphite,

then install intake on exhaust vlv body leaving bolts snug but not tight.

install assembly with new intake gaskets using pilot rings to center.

exhaust gaskets are not used, coat surface with graphite and oil,

tighten manifold to head studs 25-30 ft lbs

tighten exhaust manifold to vlv body 25-30 ft lbs

tighten intake manifold to vlv body 15-20 ft lbs.

-1951 buick maintenance manual

If anyone wants I can upload image of page later after work.

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