30 November 2006, 20:47
Yes, Jan Willem, welding the cracks is, and would be, a viable option.
I did not have the cracks welded on those manifolds because I wanted to see if the porting of the outlet and the reflattening of the four flanges' surfaces would slow down the cracking, or stop it altogether. So far, I have seen no evidence of the cracks that were on the manifolds that I did getting larger, or leaking any exhaust gases out. The cracks are still there, and they have not gotten any worse.
...of course, it could be surmised that I did not have the cracks welded because I am some sort of cheapskate, and did not want to spend the money for the welding. [haha] That was a minor issue; but to see if the manifolds could be saved and reused just by the other procedures was the main reason I did it that way. I did not know if it would work out at the time. I wanted to find out.
Welding cast iron is as much art as it is science; and finding a professional welder who can do the work successfully is a very good find. Definitely. Not too many welders will take the time to do the preheating correctly, do the welding, and then do the cooldown slowly enough to allow the iron to cool off without re-cracking, or inducing new cracks.
If the cracks can be repaired, then along with removing the causes of the stress that leads to the cracking, such a repaired manifold should give many years of service.
So, the way to go about it with a cracked 90+ manifold would be to have the cracks welded; and then port the outlet and reflatten the four flanges. Such an approach should correct the problem; and result in your having a very good manifold that performs well: better flow and more power.
TF
I did not have the cracks welded on those manifolds because I wanted to see if the porting of the outlet and the reflattening of the four flanges' surfaces would slow down the cracking, or stop it altogether. So far, I have seen no evidence of the cracks that were on the manifolds that I did getting larger, or leaking any exhaust gases out. The cracks are still there, and they have not gotten any worse.
...of course, it could be surmised that I did not have the cracks welded because I am some sort of cheapskate, and did not want to spend the money for the welding. [haha] That was a minor issue; but to see if the manifolds could be saved and reused just by the other procedures was the main reason I did it that way. I did not know if it would work out at the time. I wanted to find out.
Welding cast iron is as much art as it is science; and finding a professional welder who can do the work successfully is a very good find. Definitely. Not too many welders will take the time to do the preheating correctly, do the welding, and then do the cooldown slowly enough to allow the iron to cool off without re-cracking, or inducing new cracks.
If the cracks can be repaired, then along with removing the causes of the stress that leads to the cracking, such a repaired manifold should give many years of service.
So, the way to go about it with a cracked 90+ manifold would be to have the cracks welded; and then port the outlet and reflatten the four flanges. Such an approach should correct the problem; and result in your having a very good manifold that performs well: better flow and more power.
TF