At 05:26 PM 10/5/99 +1000, Neil Cotty wrote:
>....
>The thermostat housing studs on my A's Cylinder head are stuck fast. I've
let them soak in releasing agent for 2 days and they still won't budge.
Where do I go from here? It's not looking good.
They rust in place because two of the tree holes go through into the water
jacket so water can work up into the threads with pressure in the cooling
system. For the future it's a good idea to use thread sealer or anti-seize
compound on the threads in the head. Meanwhile, ....
If the penetrating oil doesn't do the job it's time for heat (before you
break the stud). Put two hex nuts on the top of the stud and jam them
together so you can apply torque with a wrench. Heat the stud at the
bottom, as near to the head surface as you can, until it begins to glow a
dull red (not hotter), and then try unscrewing it with a wrench.
If that doesn't work, you are ultimately doomed to breaking the stud and
having to drill it out and clean up the threads with a tap. If you screw
that up you can still install a helicoil to restore the threads.
Alternately there are shops with an ELOX machine (Electronic Discharge)
that can burn out the core of the stud and leave only the thread which can
then be picked out of the hole. This process of course requires you to
remove the head from the engine and take it to the shop.
>What is a stud extractor, will it work?
Two definitions here, one that just grabs the stud to make it easier to
wrench, and one that is intended to remove a flush broken stud. The
wrenching types (several styles) probably won't get you any farther than
double nutting, but may be easier to use. For the broken stud the idea is
to drill a pilot hole about half the major diameter of the stud and use a
EasyOut to unscrew the remaining portion of the stud. EasyOut looks
something like a slightly tapered reverse twist drill bit, but generally
square or six sided with sharp corners. These sometimes work for a stud
that was broken during installation where it's just screwed in snug but not
rusted in place. For a rusted stud you're more likely to break the tool
off in the hole than to get the thread loose, and as the tool is hardened
it can't be drilled out, so then you're stuck with the ELOX option.
>I don't own a welding torch (yet) but could a butane type blowtorch heat
the things and give me a hand that way?
Butane or propane would probably work, but you need to get the stud glowing
dull red, and the cylinder head itself is a great heat sink, so an
acetalene torch is much quicker.
>How about drilling the buggers out?
Yup, can do, but it's rather a PITA, so only a last resort when all else
fails and you finally break the stud. Start by grinding the exposed end of
the stud flat, then use a center punch to mark the center of the stud as
best you can. Start with a small drill bit to make a pilot hole, drilling
all the way through the length of the stud. Then use progressively larger
drills to enlarge the hole. When you get close to the thread go in small
steps, like only 1/64" larger drill with each pass. When you can first see
a little of the thread exposed on one side of the drill hole you stop
drilling and clean out the rest with a tap. And if youend up too far off
center and screw up the thread in the head, then you're back to the
helicoil for a repair. Such fun, these old cars.
Good luck,
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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