|
Post by newforest on Dec 22, 2021 20:04:40 GMT
Hi
Has anyone successfully welded an exhaust manifold? A new one seems to be £390!
I tried to attach a photo but gave up!
It's cracked by the single hole closest to the front of the engine. Do you think it's been over-tightened?
Many thanks
|
|
|
Post by djm16 on Dec 22, 2021 23:00:14 GMT
It is possible to weld cast iron using special welding rods so that the weld material shrinks as it cools at the same rate as the cast iron. However, an exhaust manifold has been through thousands of heat cycles, is porous, is thoroughly impregnated with contaminants and is starting to degrade into a more fragile crystalline structure. Plenty about it on the net, here for example: www.muggyweld.com/video/weld-exhaust-manifold/And yes, overtightening an already distorted manifold can cause it to crack. I occasionally have mine resurfaced to avoid this problem.
|
|
|
Post by enigmas on Dec 22, 2021 23:57:11 GMT
Yes, any "authentic" engineering/engine reconditioning shop can do this. If you can use an oxy/acetylene set you can also braze repair the manifold using "bronze" welding rods.
Method. Grind the area clean first, then create a wide V groove into the broken or cracked piece/section. If you can preheat the complete manifold initially. Stick it in the oven. You want it hot but obviously not so hot that you can't handle it with a set of protective gloves or similar method for removal.
Using a large welding tip heat the repair area until the bronze starts to flow into the join. This will take considerable heat from the torch and into the repair area. Puddle the bronze into the cavity so that it is slightly above the surface. Once done, allow it to cool slowly. Do not rapid cool the repair. When cool, grind and linish the area.
The bronze will not melt out of the repair. Header flanges and race car manifolds were made like this prior to the use of MIG and TIG welders.
PS. Your repair area seems to be quite small from the comment you've provided. If it affects the flange mating surface have it machined true after the repair to the cracked area is completed.
|
|
|
Post by Phil Nottingham on Dec 23, 2021 5:53:01 GMT
The manifold often cracks or distorts through overtightening the clamps which prevents the necessary expansion when hot. The special clamps are often fitted back to front with the nut land facing the block instead of its curved face. Welding can be done and is worth trying
|
|
|
Post by Jens Munk on Dec 23, 2021 10:24:13 GMT
You may be lucky and get a good one on eBay. At least I was recently lucky to acquire a set when I discovered a crack.
|
|