I was reinstalling the thermal reactor on my 79, in bolting it in, I noticed the threads are different sizes. Ones shorter than the other and takes different size bolts.
The shorter threaded post has no bolt and nothing I’ve tried fits.
You guys run into this?

 

Are you talking about the 4 studs connecting it to the engine block, or the 3 studs connecting it to the rest of the piping after it?

 

Mine has just 2 studs on the ‘output’ side. One is shorter and requires a slightly smaller bolt than the longer one.

 

SA Thermal reactor on left w/ 3 studs. FB exhaust manifold on right with 2 bolt holes. I don't remember if my manifold had matching bolts/studs or if they were different like yours.

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My bad.. not the reactor but the section the air line attaches to just past the reactor. That part has the 2 different studs on the output. The input bolts to the reactor.

 

I just installed my engine and TR in the 1979 this week. I have four studs and the nuts are 10x1.5 (course thread) if I remember.

 

The threaded post closest to camera is shorter and different size.. bolt on the other one is too big for it.
weird.

Just for the helluvit I tried the steering wheel bolt .. darned if it didn’t fit!
I’ll match that up at HD or elsewhere.

 

Let me piggy back on this and ask - what is the thread pitch for the SA thermal reactor to downpipe studs?
Thanks.

 

That looks like your heat exchanger to me, not the thermal reactor. Both studs should be the same not different. Is it stripped? Measuring the diameter with a mic or pair of calipers will give you the diameter and a thread pitch gauge will give you the pitch (threads per inch).

 

It's definitely not the TR; I was guessing it was the tail end of the CAT. What's a heat exchanger? The picture kinda looks (to me) like the closer stud is an actual stud (with damaged or dirty threads) and the farther one looks like a bolt/rod JBwelded in place.

 

Please replace thermal reactor for exhaust manifold or whatever this goofy looking part is called

 

Yeah it's not a TR or an exhaust manifold. It's something mounted behind that, like a CAT, except it looks too thick-walled (to me) to be a cat.

OP, do you have any better pics of that thing and it's location relative to the plumbing ahead of it?

 

Stock SA systems don't have cats. They have a heat exchanger btw the head pipe and main pipe running back to the muffler. I checked a spare heat exchanger and both studs are 12mm X 1.25 pitch.

 

No doubt someone monkeyed with the studs, one maybe broke and was “replaced”.. it seems solid so I’ll find bolts that fit and go with it.
Thanks guys!