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Straight 8 Exhaust Leak

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I have a 1950 Special, I've read dozens of exhaust manifold leak topics, and I thought I had everything under control this time. Initially I just changed the old exhaust manifold gasket with a new Felpro gasket.The exhaust leak close to the firewall was still there. Next I took the manifold and the manifold valve body to the machine shop. They were both surfaced and repaired. There were some small cracks around the studs of both. I put everything back together with a set of copper gaskets, everything seemed to seat nice and tight. Started the car and discovered that there was a gap on the bottom of the manifold at the head, and at the bottom of the exhaust manifold valve body. All the surfaces are perfectly flat on the bench, so I'm at a loss why everything does not line up. I don't want to have to buy a reproduction exhaust manifold, and manifold valve body. Without seeing, does anybody have any suggestions? Also, were the components interchangeable back to 1939? I turned a small exhaust leak into a big exhaust leak. :(

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The Hollander 1952 says the single carb. exhaust manifold #1314135 fits series 40 and 50 from '39--51 (maybe later - that is where my book ends).

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The old trick was two gaskets.  There must be  something holding the manifold up from sealing correctly. Try putting on the manifold on without any gasket.  You should be able to hold it tight to the head without rocking.   I would use two nuts to hold it in place, slightly in from each end.  If you shine a light from the bottom you should be able to see anything holding the manifold from seating correctly.  My guess is something is holding it from seating.  Remember when they ground the manifold it got thinner, might need some washers to stay on the threaded part of the old studs.

 

Good luck

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Remflex gaskets. I swear by them. They're not correct for a Buick straight-8 (the factory did not use gaskets) but I use them now because the parts are old and imperfect. The Remflex gaskets are 1/8" thick so you have plenty to work with if the surface is uneven. They torque down to 1/16" but they recommend 20-25 lb-ft torque, so they don't need to be super tight. They do make a set expressly for the straight-8 Buicks and they only cost about $45/set. I have used them on my wife's 1956 Chrysler manifolds and have a set waiting to go on my 1941 Limited when I get my header(s) back from the ceramic coating shop. They work as advertised (Google them). Much recommended.

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