Exhaust Manifold trouble

I had to remove my manifold again because I couldn’t make any progress with the bolts.


The threads looked stripped, I should have known from the first time that the threads were somewhat compromised.

So I ordered new bolts and nuts , I found a shop that will remove the bolts , the owner (old timer) sounds like he knows and has knowledge about removal without cracking the manifold. Any suggestions are appreciated , thanks Benny

BF gas axe, vice grips, MUCH patience.

After the new studs are replaced check the flange to make sure they are flat.

Seeing that you are replacing the studs just weld nuts to the studs. The heat from welding might help in removal.

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And don’t use a impact gun

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Thanks for your suggestions. Does anyone know which tap size I need to get to clean up the threads?
For the new bolts.

Inspect the top of the stud carefully for any burr, or staking, and if found, relieve it with a dremel or drill bit

It will expand and crack the corner if not attended

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Good point Tony

3/8-24… and use antiseize.

Thanks Paul. I was thinking the studs could be about 1/4 inch longer. What do you think of
putting a BB or something in the hole before the stud.

I broke one cause of (what appears to be staking), of course its the last one after you have got the others out

In addition, it seems to me they can become brittle & porous with age, not a good combination

therefore putting a side load on the stud is to be avoided, just something to think about

I would weld a nut onto the studs, and probably could get away with butane torch to expand corners. (if I did not have oxy, which I dont at present).

I would heat cycle them over & over, until penetrant can be seen to bubble on the junction, that means it has penetrated

Then work them very gradually back & forth

Dont drop one on a hard surface

amongst my manifolds, there are many with a broken corner

Not sure why, but it is a warning to be careful

an arc welder can be used as an instant induction heater on the stud once the nut is welded on, with a bit of finesse :rofl:

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  1. if I am understanding you, you’re suggesting putting a BB underneath the stud in the bottom of the hole?

  2. If that is correct, I have absolutely no idea what benefit that would provide, and

  3. The holes are open so the BB would fall out!

 if this one breaks there aren't available

to be used as a stop for the stud a BB or bearing. the hole comes to a taper at the end.

If we are talking about the cast-iron manifolds, where the two down pipes attach, I never saw any of them that had blind holes in them.

In any case, a BB at the end is not a good idea, because it minimizes the number of threads that the stud can hold onto: you want it in there as far as you can.

One thing you can do, that I believe would aid in success, once the top of the stud/hole is cleaned up, no burrs

drill a narrow hole down into that part of the start, only about 2mm deep

This slightly relieves the expansionary pressure the top of the stud exerts as it winds its way down

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Hey Benny:

I posted about this on another thread a couple of years ago about broken exhaust manifold studs. I saw this done by repair shop many years ago where the broken stud was drilled down the center leaving the threads in place and then hitting the remaining piece with an oxy acetylene torch - after a few seconds of intense heat the stud blew straight out onto the shop floor as molten lava leaving the inner threads completely in tact. The master mechanic even gathered his crew around for a “watch & learn” moment. It was very cool to see the reaction of the group as they had never seen this trick before and neither had I - it was so simple and very impressive! Maybe your guy, being an old hand, will be taking a similar approach. Cheers.

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Yes maybe I’ll ask about his procedure. Meanwhile I just noticed that the new joining plate is over 3mm
thicker than original which gave me more bite on the threads. If I can fix the threads I’ll use the old plates.

Have you the correct manifold nuts yet ?

see recent thread/s

I believe the ones I have at hand are “sintered bronze”, they are like the originals, much “longer” than a regular nut

…and I will also use nordlock washers for the downpipe studs

Yes I just checked they are open and some bolts are deeper than others.