New exhaust manifold for 180-190-190XT gas engine?

A friend of mine was looking for a new 190 gas manifold a few years ago. He bought the tractor cheap with a bad manifold. He is a decent welder and finally repaired his becasue he couldn't find a replacement.

Well, you might be right in theory, but you cannot time the ignition at anything faster than 25 degrees BTDC or the detonation will destroy the pistons. I know this factually from replacing broken pistons. I'm sure a good operator that lets the engine slow idle for a couple of minutes before shutdown would help reduce the castings cracking, but it's a known problem from back in 1964 up to the end. They made one manifold casting change (in the 70's) to try and help and I'm sure it did, but these days there's nothing new or good used available it seems. I'm beginning to wonder if i can even get the gasket that goes against the cylinder head. I'd rather start with new steel and fabricate something that I know will outlast a 50 year old casting that has been cracked and welded up as a repair.

Edited by DrAllis - 9 hours 13 minutes ago at 8:17am

Just farm tractors. I've built puller manifolds out of the same materials without any failures, but admittedly the 1700 degree temps only last for 10 seconds and then cool down driving back to the pits. Anyway, this will be fine as any of these gas tractors aren't plowing and discing anymore. it's just nice not to hear constant cackling coming from the exhaust manifold. Sounds like Jed Clampetts truck......