Re: Stuck bolts in aluminum.....

[Simon Favre <simon@xxxxxxxxxx>]

I believe the process is called Electron Discharge Machining (EDM). I have
yet to hear from anybody who has successfully used this on Alfa head studs.
Intake and exhaust studs, yes, but not head studs. The problem is that the
head studs are down in the bottom of a well and they galvanize themselves
into place so well that even if you could get one out, the new one may not
hold. For 2L blocks, it's usually cheaper and safer to just get another
one. As the supply of early 1300 and 1600 blocks dries up, this may become
a viable solution. I can see, though, that if you have to have ARP make up
some head studs with special oversize threads at the bottom to make them
hold, you're talking second mortgage.

As I understand it, EDM depends on the fact that Aluminum conducts heat
much better than steel. The steel gets heated so rapidly, it vaporizes, but
the Aluminum never gets hot enough to melt. The water spray obviously helps
drain the heat out of the Al. With Alfa head studs, the galvanic action in
the hole may seriously detract from the heat conductivity of the Aluminum
right at the point of contact. This may make EDM unworkable.  Add to that
the fact that the galvanic corrosion in the hole may reduce the current
carrying capacity of the steel/Aluminum interface and you have another
potential problem with EDM. The electricity has to come out the other side
of the joint.

Digest poll: Has ANYBODY done this to replace a broken Alfa head stud? Did 
it last? How much did it cost? Where did you get the new stud?

Jim Barrett wrote:

>(Alert! First posting after lurking, then firewall exchanged)
>I had the same problem with with steel studs embedded in aluminum motorcycle
>cases; a motorcycle shop referred me to a local (So. California) shop
>(Jerry's Drill and Tap Removal 714/ 836-6824) that used a combination of
>serious DC voltage and water spray to dissolve the steel bolts. The process
>is kinda wild to watch, and it leaves the aluminum undamaged!

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