The Stovebolt Site Forums The Shop Area Engine Shop manifold gaskets

I replaced the manifold gaskets on my '46 235 a few weeks ago. I've driven the truck maybe 150 miles and it's leaking again. I have tightened the mounting bolts several times and it sounds better for a day or two, then they're loose again. The manual just says to make them tight, there is no torque specification. How do I keep the bolts from loosening?

Have you had this manifold off? Did you check its edge for flatness? I would bet that yours is warped a bit and probably will never seal unless you have that edge planed. Jerry

I also have a 51 Chevy 1/2 ton, 235. Have replaced the exhaust manifold gaskets and have tightened and retightened.
How would one go about having the manifold edge planed? I am with the idea that a machine shop can check for the flatness and can plane the edges. Am I correct?

most good machine shops can plane the surfaces.
You should check first to make sure the two manifolds are bolted together with the faces in line. I see a lot that are not.

Well, I finally tore into the project today. I only had to drill out and retap 3 bolt holes. The manifold checked out nice and flat when I checked it with a straightedge. Since the gasket set included the one that goes between the manifolds for the heat riser, I took them apart and reassembled them to the engine before tightening anything. Everything went together well and it runs quieter than ever. I'll let you know in a few weeks how well it holds up.

Just my 2 cents on this: Undoing the bolts at the heat riser allows each manifold too set better against the head. When the heat riser is tightened up all of the misalignment is taken up at the junction of the heat riser and not at the head. It worked wonders on my 235. I had to remove and replace the exhaust manifold due to some broken bolts. With the manifold apart I could check each piece for true and flat at the head flanges. Intake was good and exhaust was good. When they were bolted together they were not. Kid of a twisted and misaligned if you will. So I put them on while the heat riser bolts were loose. Worked very well. Snugged up the heat riser bolts and nothing moved. Started and was quiet. No more leaks. Drilling and re-tapping holes? Good argument for anti-seize for sure.