Standard Engine Exhaust Manifold Thread Restoration

Thanks for all the replies.
I figured out what was happening and have a solution. When I pulled the pipes off I noted the threads lost a lot of depth. The old pipes had stainless nuts and I thought that may have been part of the reason I lost so much thread depth so I was planning on using some brass nuts that I had. When I tried the brass nuts they had little to no grip in the manifolds, hence the request for suggestions on possible solutions. Jim's initial suggestion of having them machined and re-threaded to a larger diameter was the key. I couldn't understand why I had lost so much depth that the brass nuts sort of flopped around in the manifolds so I checked the brass nut diameter and stainless diameter and found that the stainless were significantly larger. After pulling the stainless nuts off the old pipes I found they still had significant thread engagement. Bottom line, the manifolds had evidently received the machine procedure and oversize nuts Jim was suggesting(40 years ago when the drivetrain was last rebuilt). It appears that the stainless nuts will provide sufficient compression for a good seal. I am using never seize on the threads this time so no additional thread depth is lost in the future.

John, my temporary fix is ugly but works for the car untill I get the refurbed manifolds.


2 exhaust pipe clamps, some thick rings, bolts and a welder is all you need.

Frank

Thanks again Jim.

Hi John,

The other fixes I've seen involve machining clamps to hold the packing nut in the exhaust manifold. This involves considerable machining and fitting. Some have worked very well and others not so well.

Timing wise you'll probably have the same amount of time in jury rigging something (less money) as you will pulling the manifold and sending it out.

Either way good luck.

Jim

Thanks for the quick reply Jim. It sounds like it is the best permanent fix possible and something I need to accomplish in the final analysis.
In the mean time I find myself behind in my self imposed schedule to get the car back on the road by Memorial day. It missed the local parade last year for the first time in 17 years and some of the locals were concerned about it's health and well being. I also normally take it to local shows and cruises to allow people a chance to appreciate some rolling sculpture and I need a Cord fix.
Since this is only one of the many issues that have arisen with my "simple" conversion from rear back to front wheel drive, I would entertain any potential fixes that might be quicker if less permanent, that would allow me to meet my schedule. As the optimist said "I can always do it right next winter when that's the only issue I'm facing".

John,

Your best bet is to send the manifolds to Brian Joseph. He has a special die to cut new threads (oversized) and he make new nuts to with with it. I just had a set done recently and they came back like new.

Jim

The threads in my 810 cast iron manifolds lost a lot of thread depth when I unscrewed the brass nuts holding the old exhaust pipes. I doubt that I can get enough compression force when I install the new pipes to get a good seal. Does anyone have a procedure to restore the threads? The manifolds are otherwise in good condition.