I seem to write this up about once a year; maybe one of these times I'll
remember to save it. I looked, but can't find it on the SOL tech tips web
page...I've used the methods described below on exhaust manifolds, cylinder
heads (in place!) and myriad other things with great success (but not
necessarily great speed).
Greg's method will work if there is metal from the stud sticking out.
Unfortunately, that's not usually the case. Then, you have to drill it out. For
this, you need
patience
reversing drill
left-handed drill bits
sharp punch and hammer
patience
torch
penetrating oil (I think Kroil is best)
patience
torch
ez-outs
hammer
patience
tap for the thread
patience
A scribe and a small round file may help. You might want some extra patience,
too. If you get frustrated in the middle, take a break and come back to it the
next day.
I start with heat. Heat the stud and manifold as hot as you can; getting the
stud to glow is a good start. If you only have a propane torch, get a MAPP
bottle (sometimes sold under different names) which gives an appreciably hotter
flame. Let it cool a bit, then spray the penetrating oil. Repeat this a couple
of times. You're trying to do two things: break the rust bond and anneal the
stud.
Use the punch to punch a hole as close to the center of the stud as you can. If
the stud broke off unevenly (and they always seem to) this is especially hard
and especially important. Make the punch mark quite deep, so the drill bit
won't be tempted to wander.
Use the smallest left handed drill bit you have, and drill completely through
the stud. Drilling left handed is important because that's the direction you
want the stud to turn - sometimes the heat and vibration from this step will be
enough to break the bond and the stud remains will come out with the bit. Don't
count on it, though.
Work your way up through the available drill bits. When you get close to having
removed all of the center of the stud (but before you damage the threads in the
manifold), it's time to try an ez out. But first, go through a couple more heat
and oil cycles.
I have never decided whether I like the straight flute or twist flute kind
better, but I've lately been leaning towards the straight flute. Put the sucker
in place, use a hammer to drive it fully home. Apply torque. If you're lucky,
the stud will actually come out. Don't be surprised if it doesn't. Try not to
break the ezout; that'll just make the job more annoying.
(There is a new generation of tools that combine left handed drill bit and
ezout and even claim to center themselves. They're very expensive, so I haven't
tried them yet. They just might make this job a little easier.)
I will usually try a small impact wrench at this point: find an 8-point socket
that fits over the square end of the ezout and blast away. This sometimes
works. Don't be surprised if it doesn't. And, again, try not to break the
ezout.
If you're now to the point where the next larger drill bit will start removing
threads, you have to proceed carefully. You can get away with removing a small
amount of the crest of the thread - this will make the stud fit a bit poorer,
but probably won't matter much. If you go this route, you will probably be able
to break a portion of each individual stud thread out of the manifold threads
(this is where the scribe comes in handy). At this point, you can try using the
hammer and punch to rotate the fractional piece of the stud in the threads.
You can also take the file to the hole and enlarge it, and then try the two
above methods.
Finally, you can use the file (or a small grinding point on a Dremel) to remove
the first couple of threads of the stud (using the scribe to pick the pieces
out of the troughs of the manifold thread). Now use the tap to essentially tap
a new hole - you want to go about 1/8 turn at a time, cleaning the tap every
time. You'll probably lose the first couple of threads in the manifold, but
that shouldn't matter much.
When you get it all done: make sure you use anti-seize on the new studs before
you install them, so you (or the person you sell the car to!) won't have to go
through this the next time. Use brass or stainless steel nuts and lock washers,
so they don't corrode in place (TRF sells the brass nuts, as do most auto parts
stores; go to a marine supply for the stainless kit). ARP is starting to
manufacture stainless studs for British applications, but I don't think they
have any for Triumph yet.
|