I got my manifold back from the machine shop. He surfaced it nicely and sand blasted the rust off it so I can paint it. But there's a problem. THere's a crack on the port side of the manifold. It's not too bad, about an inch and a half long, and it's pretty much hairline now. What should I do with it? I had to take the manifold off because of an exhaust leak where the gasket disintegrated. With it being so small, will it stay without growing? Or should I try to weld it? Mostly I think I shouldn't mess with it. What about putting some jb on it just to keep it from growing? I'm not going to be racing the car or anything, just cruising with it. And Eventually I'm going to pull the engine and have it rebuilt, maybe put headers on it then.
Tom, Is it for a 350 or 455? I may have one that I could sell you at a reasonable price and am pretty local.
Welding or brazing cast iron cracks will not stop them from returning. Every time you start that engine the exhaust manifold grows and then shrinks when you shut if off. This flexes the repair, eventually cracking through and it will also continue to get longer as it flexes.You need to cut clear through the crack and probably drill the end of it and then weld it 100% so I will not reappear. If you are going to braze it, drill the end of the crack and you might stop it from getting longer. I see this as a temporary fix. BTW, I have some know of the subject as I was a certified welder and I at one point passed the American Welding Society Inspectors test. But this is just my humble opinion and two cents worth.
Heat it up slowly to a dull red and then weld it with a cast iron rod or a stainless steel rod and then let it cool slowly....
It's for a 350, driver's side. I'm taking a welding class right now and we can bring in stuff to work on as long as it's small. I just don't know that I'm good enough to drill it and weld it and do everything Kurt suggests. I'm not in a hurry, the car's not running now anyways.
If your taking a welding class now maybe ask the instructor what he suggests and take Kurt's and Docs advise heck your instructor may weld it up for you as a class show and tell. I'd recommend drilling the ends of the crack reguardless, maybe 1/8-1/4" from the end of the crack you see kinda guess in the path it's going. If your welding place has an oven your set. If you can't get it welded cheap Find a new manifold.
Keep the entire manifold hot while repairing it or it may warp and need resurfacing again. I had one repaired and it never cracked again.
Replace it. As you have already seen used ones aren't hard to find or expensive for the 350. Though I have seen them welded successfully by professionals, its not worth the effort unless its a rare piece. If you did weld it you would have to get it resurfaced and squared up again.
