Exhaust Manifold

I just spent a couple evnings with a friend who welded my cracked manifolds to perfection. They are now much stronger than the originals, because he built up the areas a bit where they were quite thin, and prone to cracking, such as the valley in the top of the exhaust manifold in the two center ports. He then carefully re-shaped and sand-blasted the welds to make them dissapear, and blend in to the rest of the casting.



This is not a cheap project however, it takes a great deal of set-up, and some machining afterwards to true up all the faces and make sure there is no stress in the metal left anywhere.



The process requires an oven that enables you to get the whole unit red hot, and then open up the oven just enough to work on the unit while its still in there retaining as much heat as possible, by firstly grinding out all cracks to about 1/4 inch wide, and cut completely through, and then puddling in the special rod, using a special flux to make it bond, while melting it down with an acetylene torch. The process is not unlike leading was done in the old days on body work, and the results when done by a skilled professional are simply amazing!



Frequent heating to keep the unit very close to red hot is required as the welding proceeds, and when all is done, the whole unit is re-heated to red hot again, and then imbedded in powder to be left overnight to cool evenly, and very, very slowly.



If you paid the man fair and square for all the effort required to do this work, it'd cost more than a good used manifold, so that's the better option if you have a source for another.



Don't throw those cracked ones away though !! There's at least one Guy out there that can repair them to better than new condition. He can also do engine blocks, heads, etc., but again, the cost of labour these days prohibits doing this work unless you have an irreplaceable original you want restored to concours condition.



I'll be putting this manifold in my car tomorrow, and should have a couple pictures then. Its a thing of beauty !



silverone.

I had someone weld my cast iron ex. manifolds.[they can weld cast iron now with special rod] I spotted them in ,[machining of course is a better job] but this six takes a gasket ,a thick one at that, so i'm sure spotting with some prusson blue would suffice. Came out real nice. Make sure you vee out the cracks real well. The welder that did these said it was the poorest quality cast iron he'd ever seen.

Harry Hill wrote:

A friend of mine welded up my exhaust manifold this weekend using a torch and a powder that flowed into the flame from a bottle mounted on top of the torch. The stuff just flowed into the piece and made it whole again, amazing stuff, then he wrapped the manifold in insulation and let it cool over night, no cracks and no warpage, I broke the flange right at the butterfly and it is whole again.



Harry

This sounds similar to the process I watched a friend do on my own manifolds a week or so ago. However, he melted in a type of 3/8" square rod that looked like some sort of cast material itself, ( expensive stuff - 200 bucks for a pack of twenty about 14-15 inches long ), along with the flux that he kept dipping the rod into to keep the metals mixing and flowing. The flux looked like a reddish powder of some sort.



Maybe because he vee'd out the cracks before hand, right through to the other side, he needed the rod to replace the ground away metal, and to build up some weak and thin areas where he felt a little reinforcement might prevent future cracks.



He says you do not leave any of the old crack anywhere before welding, and he even drilled the ends of each crack as well, so that nowhere was there anything that could start the crack again, topside, or underneath. All new metal is thusly bonded to only only freshly ground edges.

If you dont' want to weld your manifold, I think i have a couple of them here. Let me know and i will see what i have.



Paul