[DML] Refined Procedure: Removal of Broken Exhaust Manifold Stud
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[DML] Refined Procedure: Removal of Broken Exhaust Manifold Stud



After reading the other replies, I realized I should provide additional
info on my experience with removing the exhaust manifold studs from the
block.  I've tried a lot of different techniques over the years
starting with a 62 F-85 aluminum block while a teenager.  I would
summarize what I've learned as follows.

1.  The best ways to break loose the bond between two metals are heat,
impact and penetrant.  (I'm still amazed at how a couple of firm hits
to the side of the steering knuckle will loosen a tie rod end!) 
Hitting the end of the stud (assuming there's something to hit) is the
start of an insurance investment against the stud breaking in the
block.

I feel the next step to breaking the bond should be applying heat.  A
propane torch may not provide enough heat but a mape gas torch will. I
suggest using a torch that has a flex hose between the mape gas tank
and the tip to fit better into the tight space and keep the tank
upright.  A mape torch is also an inexpensive purchase compared to an
oxygen acetylene torch.

After heating the stud, I let it cool then apply penetrant a few times
over 2 or 3 days.

I've NEVER broken a stud off in an aluminum block using these three
steps before attempting to remove the stud.

2.  If the stud is broken inside the block, I've had the best success
with the following:  a) as someone else suggested, carefully center and
tap the stud with a punch to provide as accurate-as-possible center for
drilling but also to help break the bond as mentioned previously. b)
heat the stud, preferably to point of just beginning to turn red then
remove the heat and let cool. c) after cooling, repeat hitting the
broken stud with the punch.  Then, apply the penetrant for a couple of
days as mentioned above.  

d) At this point, I also use the reverse drill bits making sure I stay
in the middle of the stud.  I also ream the hole as I drill so the bit
does not bind so tight it cannot be removed if it breaks.  The previous
heating of the stud seems to soften the metal and make it easier to
drill.  I start with a smaller bit (about 1/8" and get progressively
larger.  I've found that about half the time, by the time I've almost
finished drilling with the second bit, the stud drills itself out of
the hole!  I suspect the impact of the reverse drilling also helps free
the stud.

As Dave T. mentioned, it's a real pain to remove an Easy-Out that
breaks in the process.  I've heard that some machinists use a torque
wrench to keep this from happening, but I've found the best way to
prevent this is to repeat the heating and penetrant.  I like
"Knocker-Loose" but this is in no way a scientific conclusion.

Dave T. is also correct in his concerns about damaging the Al block
with a cutting torch.  Had I not seen it done before attempting myself,
and if it had not worked for me on several occasions, I would not
believe it myself.  Despite my success at removing the studs with this
method, I'm not suggesting this method be attempted by someone not
skilled with a torch, nor should this method be used prior to
exhausting the other alternatives mentioned above.  I've always used a
small torch/tip, had done several on cast blocks before attempting the
Al, and all but two with aluminum blocks were done on a bench, not on
the car.  In other words, consider this a method of last resort done by
someone skilled with a torch, with the right equipment, and with the
recognition that block damage is possible, particularly if done
incorrectly.

Hope this helps,

Woody



       
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