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Re: 315 Poly exhaust manifold: POR15, weld or replace?

From: Hank Dozier
Remote Name:
Date: February 20, 2003


It probably not the welding, its the technique that killed your first manifold. It is a characteristic of iron for a crack to propgate along "slip planes", which are formed by inconsistencies in the poured material. You can most likely make that new one work by welding it in the following manner. First, locate the ends of the crack and drill a small hole at each crack end to stress relieve tha crack. It will not continue past this point if you have the end. The hole can be samall (0.10", maybe less). Now V-groove the crack and cahamfer the hole. Heat the manifold in an oven to 400-500 degrees, and weld it HOT with a high-nickel content rod. Gas weld is best, but electric (flux wire-weld)will do if the current settings are right. Find a good welder for this operation. Straight out of welding, back into the oven for a couple of hours to normalize, and then shut off and let air-cool. This should give a strong weld that does not crack adjacent to the weld.


Last changed: July 19, 2018