Although 'toothing' may be a contributor to the flaking, it's minor compared to the heat soaking.  Grinding and sanding in my case were simply done for appearance purposes.  Early on, this engine did considerable idling in heavy traffic and the underhood temperatures were to the extreme.  The headers on my race cars hold up quite well in a racing environment where air flow is always across the headers but whenever dyno testing, the dead air around the headers promotes higher temperatures that ultimately dulls the finish.

Lorena, Texas (South of Waco)

Right now I am awaiting another ECJ-9431 (LH bird manifold) to check out, as the one that was running on the engine showed a crack when tested with penetrant. It is a real crack not a false indication (#$^@*)! It isn't un-repairable - but I'm not too keen on coating a less than perfect specimen. The RH side checks OK. 

Is there a weld procedure published anywhere that is specific to the Ford cast manifolds? In particular - the preheat and suggested filler material. I have a manifold (RH) that has obviously been repaired - and with some finish grinding and close inspection it looks like it will work as a spare. Either "someone" knew the drill and how to do this - or there are some tech spec's I haven't found. When we fix alloy steel castings at our place, we usually take the part up to 450° F soaking, wrap and shield everything but the repair site - then armor up the welder himself with a reflective guard. But we usually know exactly what the casting is made of and other important details. 

  

 
 Steve Metzger       Tucson, Arizona

      A preheat with a torch and a high nickle rod works on the intakes. I'm guessing (?) that those exhaust manifolds are gray iron too. They didn't start to specialize materials until a number of years later. Now they're all hydroformed weldaments anyhow.

Frank/Rebop

Bristol, In ( by Elkhart)