MTFCA Forum

Knowing that if you stack-up enough time, money and skill, anything is possible; What is the viability of thread repair on an original exhaust manifold?

The only reason that I am asking is that this is a Made In Canada manifold and if it weren't for that, it would have ended up in the scrap barrel, straight-away. Aside from the "minor" loss of the threads (and a slight bow) it is a good looking manifold.

I know that a manifold can be straightened, but good quality reproductions are available, I don't think so for ones marked MADE IN CANADA. So, is it worth offering this project up to anyone (I'm looking towards my neighbors to the South in Canada with a side glance over to Australia) or should it just make it's way to the scrap bin? Also, How would you attempt to repair the threads?

It would be easier to buy a new repop manifold & have the "made in canada" engraved into the new manifold.
More than one way to skin this cat.

I don't know how common "Made In Canada" exhaust manifold are? Repairing one with bad threads (and then if you needed to straighten it?) is not an easy or inexpensive task.
One could custom make an undersize thread cutter and exhaust pipe nuts? But even that wouldn't be cheap.
Cutting the "Made In Canada" into a modern reproduction manifold would be simple enough if a CNC machine could be programmed to do it? However the model reproduction manifolds aren't quite that same in details as the original manifolds. Also, making the machined in lettering look like natural casting would be difficult.

Neat curiosity piece regardless.

Would it be possible to section and weld the stamping onto a clean manifold, hate to cut an original manifold but it may be viable if it’s all you’re after.

A few years ago, a friend did a very nice weld job of a complete around break between Cylinders 2 and 3.

Then, ground off the high spots and it really looked great.

His engine over heated on the first drive and the crack came right back, all the way around just like it was before.

There must be a secret for that success!

I don't have a spare manifold on hand to look at. Is there enough space to turn the OD down and re-thread it, or press a bushing on and thread that to original size? If so, then it would only cost you your time if you have the tooling to make it happen.

The problem with engraving "Made in Canada" on a repop manifold is the castings are not the same. The repops do not look like originals around the rear port.

Allan from down under.

Thinking it over? I suspect the best (?) cheapest repair would be to machine a steel sleeve with the manifold's replacement external threads on it, and then grind carefully around the manifold and size it to heat expand and cool shrink the sleeve onto the manifold. The big fault with that idea is that the extreme heat cycles of the manifold would work it very hard to break it loose or simply break the sleeve or the manifold itself. Maybe the external sleeve could be nickel welded into place?
Some original manifolds would be too thin to retain enough strength for such a sleeve repair. The main advantage to the idea is that a sleeve could be machined easily inside straight and outside threaded on a common lathe. Although not as easy to do, the straight more or less smooth around the outside cutting/grinding/shaping would be much easier to do than cutting new threads on built up material. Thread cutters to clean up damaged threads are one thing. A cutter to cut new threads on built up and potentially dissimilar metals would be another.

Just some things to think about?

If you had the skills to weld cast iron, you could build up the threaded area, grind or machine it down to round and grinding / turning the weld back to original OD dimensions and cutting new threads. All it takes i equipment, skill, and money. Realigning the manifold isn't THAT hard given a rosebud and a gentle touch, maybe the jig built up on a vise or ??, but um, the real question is this - Are you doing a 100 point restoration on the car, or are you going to drive it?

If you're going to tackle this, find a less rare scrap manifold or 3 to PRACTICE on, get your jigs etc set up, get the welding and grinding and straightening down, then once youre confident in your ability, go for it.

And think on this - there was way more than one MiC model T out there, so this isn't likely the last remaining MiC exhaust manifold. True, you can't just go to a vendor and buy one, but they're not truly unobtanium.

They are not really that rare in Australia. One like that would be junked in preference to a better one.

Allan from down under.

Hundreds of years ago, in the 1970s, I had an unusual exhaust manifold with horrible threads, I pulled out another manifold that had the #1 port broken off but it had like-new threads. Figuring I had little to lose, I cut the good threaded end off the broken manifold and the bad threaded end off the good manifold and arc welded the good threads on the good manifold. The result was fine; no cracks, no leaks, no warping and I drove the car daily for years.

I obtained an ANCO manifold with poor/ degraded threads, so I took a warped standard manifold with good threads and cut them off. I then removed about 1/2 of the inner diameter of the replacement part on a lathe. I then carefully ground the bad threads from the ANCO manifold, checking the fit frequently. Once I was satisfied with the fit, I silver soldered the replacement on. It has offered no problems after 2 1/2 years of frequent use

Cast iron can be very difficult to work with, and old exhaust manifolds are particularly difficult. If you could find a shop equipped to do spray-welding, the thread area could be built up, then re-threaded. The process would anneal the entire casting, and probably prevent cracking. The gasket surface would probably have to be remachined. You'd probably be better off to try to find a good original manifold and apply the lettering to it with a suitable tool, then distress it to give a cast-in look.

Scott, that is what i would have suggested, but i never thought silver solder would stand the temperatures. A good few years ago I bought two lifetime supplies of silver bronze welding rods at a liquidation sale of a welding supplies company. This particular material has a low silver content tha is added to help flow the bronze into neatly fitting components like the butts on older bicycle frames etc. That would work well.

Allan from down under.

OK this is a can of worms opened up. Welding cast iron is on the list of things that no one can agree on like what oil to run, water pumps &
repairing wood wheels. I'm with Allan on the silver solder & assume Scott was referring 15% Silvaloy but if not please educate me on what you
used. Using Silvaloy I have had PP results with cast iron because they shrink at very different rates when cooling. I have never tried a repair
that involved sweating cast iron with it ??? It works very well with copper & steel tubing??? Scotts secret may save hundreds of T parts, Inquiring
minds want to know.
Craig.

The 9-N 2-N 8-N Ford tractors used a grooved clamp to hold the exhaust pipe to the manifold. If one of those will fit the pipe, filing a groove in the manifold outlet might allow using it on the T.

I’ll look when I back at my shop, I bought it at a local welding store. I don’t think the roll is in its original packaging.
Hard to say if I got lucky with it, but it has been trouble free for me.
I did consider brazing it, but for whatever reason I opted for the silver solder.
I have also for one reason or another had the pack nut off a couple of times and it is still holding strong

Scott

I’ve done what Wayne suggested with great success over the years by turning the thread off in the mill using a boring head and shrink fitting a threaded sleeve over the OD using a .003” shrink fitting. You need to make a heat sink ring to put the sleeve into first to heat as the thin rink will cool too quickly. Works perfectly

Thank you to everyone that has posted.


When I first came across this manifold in a lot of parts, the only thing that kept me from putting it in the scrap bin straight-away was the MADE IN CANADA on it. After hearing from some members more in the know on Canadian parts, while yes it is somewhat "uncommon" here in the States, not so much in Canada and Australia, better ones can be found.

If doing a fine point restoration (or just being a purist) and this is the only one available, it can be fixed. After looking through this Forum and the old Forum, there was just not a lot of threads/posts on repairing the manifold threads, this new thread has come up with some, and I am sure that they will be read in the future. Thank you again to all that posted but it is time for this manifold to move on to it's new life.