The Horror of a Busted Stud

There is nothing worse than a busted stud. Just ask any heifer.

When the going gets tough, the tough use propane. Really. There is little substitution (when you're not concerned about scorched paint or smoke rolling off of components, oils vaporizing, etc.) for the judicious application of heat when you want to get a fastener's attention.

In this case there are a dozen or so fasteners that need their attitude corrected. They're the Phillips head screws that attach the mantling at the rear of the engine. Because you must pull the engine straight back to disengage it from the transmission, these characters have to come out. They don't want to come out, and all the PB Blaster in the world hasn't convinced them. It's time to bring in my little friend, the propane torch.

I lit up the propane bottle I use for pipe sweating in plumbing applications, dial down the flame to about an inch, and then, having made sure that all pieces of flammable foam, rubber, or other materials are not near where the flame wants to work, I started by playing the flame in a constantly moving circle for a count of 30 around the bolt head. Not on the bolt head, mind you; around. The idea is to cause the metal around the bolt to expand more than the bolt does, making the captive nut that the bolt is screwed into larger as the metal expands. Then I shut off the torch and quickly grabbed my P2 Phillips screwdriver. (Phillips comes in different sizes, and each size is good for a specific torque. If you mismatch the size of the driver to the size of the head, expect to strip the head, or not be able to generate much torque.)

One hand pulling down hard to keep the driver from 'camming out' of the bolt head. The other twisting counter-clockwise as hard as I could manage.

TINK!

The bolt is loose and backs out smoothly. I won't bore you with repeated details: I performed this eleven more times, and all of the rear mantling was out. No cammed-out stripped bolt heads, no bolt heads twisted off. Yea, me.

Flushed with my new success, I decided to attack the exhaust manifold studs. These are legendary for snapping off, stripping off, or the bolts seizing solid. Probably because the engine was designed in the mid  1960s as a 1700cc, 80 DIN HP (8.2:1 CR) for the  VW 411/412 mid-size sedan series (weighing 2468 lbs.) before being adapted into the Porsche 914 and the VW Bus in 1972. By the time my 3042 lb. 1977 Bus toddled into view, the same engine had bore and stroke increased to produce 2000cc displacement, but owing to a lower compression ratio (7.3:1), and increasingly strangling emissions regulations, power output has actually fallen to 68 DIN HP. Torque produced between the original design and the final incarnation was the same, just moved lower in the power curve to help the heavier bus lumber its way up to speed.

I go into all of these eye-chart specifications because it shows how crazy things were at the time in automotive engineering. One of the byproducts of this increase in displacement, combined with lowering of compression ratio, was that exhaust temperatures skyrocketed. For the emissions, this is great. You're going to more completely burn up your fuel and spit fewer horrors out the tailpipe if you've put them through an aggressively hot engine and then designed the exhaust system to keep the temperature up in a long path to the tailpipe.

Unfortunately, one of the other things you burn up in this increased inferno are your exhaust valve seats. The original spec of this engine wasn't built for this kind of abuse, and Volkswagen's policy of using interchangeable parts to solve problems without designing 'whole system' really chewed up engines. This includes little things, too....like exhaust manifold studs. Made of mild steel and screwed directly into tapped aluminum heads, these studs were not engineered for higher heats generated by these engines. At the very least, copper nuts should have been substituted for the equally workaday mild steel nuts that were used. No such luck. So I decided to bite the bullet and as long as I had torch in hand and success under my belt with the mantling bolts, give the hot-foot to the exhaust manifold nuts a try and see if I could get them out without snapping one off.

It was nervous work, but my score was five nuts removed with studs in place, and three nuts frozen on the studs, but the studs backed cleanly out of the aluminum heads, so new studs should be easy to turn back into those threads when coated with some very high temperature Loctite. I discovered some surprises: steel nuts had apparently been replaced at different times, since about half were 12mm and the other half were the stock 13mm. (This is no surprise: the 12mm is much easier to work with, owing to somewhat improved clearance.)

But one nut was clearly larger than 12mm, but when I put on the 13mm, it just thumped around when turning. This is where I felt that 'uh-oh' sensation grow cold in me. A nut that has been so thoroughly abused and corroded that the corners have eroded right off bolt. How are you going to grab this with a socket now?

So I got out the torch again, and this time applied it to the 12mm socket on the end of a foot long extension. I heated the socket until it was smoking hot (there goes the temper on THAT socket!) Then put it over the nut and gave it a couple of mighty whacks with a framing hammer. I felt it hit home and stop moving over the nut on the third whack. When I let go, the extension hung out the bottom of the engine like a surgical instrument left in place. I took a twenty minute break and when I came back, the socket had cooled around this nut, the heat having expanded and stretched it to become "12mm plus some" and then been beaten into place around this rounded off nut. I popped the ratchet on and heaved and it didn't pop, snap or crack. The nut was so thoroughly corroded on to the stud that the whole stud just rotated cleanly out of the head. The socket is permanently attached to it. I don't care. If I have to spend $20 for a new socket set to replace one lousy socket, it is still cheaper than coping with just one busted stud.