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Douglas Kephart

Oh-oh, who is this Doug Kephart and why is he causing so much trouble!

I confess it was I that took an arc welding machine and attacked a poor defenseless Brum. Yes I did it, and yes it did work very well. I did try penetrating oil and warming the head up with a propane torch and letting it cool, to no avail. But that was it as far as preparatory work goes. I had heard of others using the hacksaw method, but even with grinding the set off the teeth I was worried about damage should the blade wander off course. The head gasket looked mighty thin, and it sounded like a very laborious task. I was afraid I would loose patience, rush it, and ruin the job. Hence my thoughts along the lines of the old electric rivet furnaces.

The reason Mike that you may not have been able to find the original reference in the Yowl is that was a quite a while ago, Vol.17: No.5, August 1991 (good grief time flies!) Second, it was buried in the middle of a three part and never finished saga on restoring my Brum. It was not an article specifically on the topic of removing stuck head studs.

Mike PM-ed me querying about the original article, and I gave him a summary of the technique and results, but I have to confess I did not check back on the forum till now (another PM) to see what came of it. Only to find I seem to have gone ‘missing’! The three Brum restoration articles and violence with an arc welder are copied in the Technicalities 9.2.18, general restoration topics.

Now to address some of the points raised, particularly the concern about melting the surrounding aluminum. There are a couple of reasons that explain why this does not happen. The stud (if stuck) is surrounded by aluminum oxide, which is a fair electrical and thermal insulator. When confronted with that route or a nice direct path down the stud and into the cast iron block, the current takes- well- the path of least resistance. But probably the main reason the alloy does not get hot, is that there just is not enough time. As I recall it took twenty seconds at most to turn the stud incandescent. No doubt some of the alloy immediately around the stud gets hot, but it does not get near melting temperature. The rest of the aluminum surrounding it is a fairly effective heat sink and the heat transfer from the stud through the aluminum oxide is poor.

I was using a 250amp arc welder. An industrial model, but since I was only using it for twenty seconds at a time, duty cycle rating did not factor in to it. I did not experiment as to how little current it took; I had 250amps on the dial, so of course I set it to maximum! The result was zero to glowing red in twenty seconds. Based on that I do not believe you need 300amps, but that would heat the stud up much quicker. I could not say what the minimum amperage required would be. If you only had say a small 125amp hobby welding machine, then it might take too long to bring the stud up to heat. The aluminum will then have a chance to heat up and expand with the stud. That still might break the corrosive bond and so enable the stud to be removed. In either case axial elongation as the stud heats up will help break the grip of the corrosion. But I think most of the gain was through rapid expansion of the stud and compaction the aluminum oxide. Then as the stud cooled, it pulled away from the surface of the hole. When I finished with a stuck stud, it actually had a slight amount of clearance in the hole; the stud backed out freely. There was a hard ‘skin’ of discolored oxide in the hole, backed up by a softer, powdery oxide. Nor were the threads stuck in the block.

Worst case is if the resistance heating was too slow, you could have time to transfer enough heat from the stud to the aluminum to melt it. But I think this would be rather difficult to achieve because of the thermal conductivity of the surrounding aluminum pulling the heat away. You would have to heat the aluminum through to the water passage right up to the melting point to get it to sag, else it has no where to go, even if the material right next to the stud did start to get a little ‘soft’. One could fill the water passages with water if it is a concern, but it may be easier to find a larger welding machine and get the job done quickly, or use the saw method. It would be a different story if the current were flowing through the aluminum. Remove the cylinder head nuts so that you do not accidentally create a circuit through the head.

One point made in the original article, but not here on this forum, is to make sure that the cylinder block is well grounded. Trying to pass 250amps through too small a contact area will cause arcing. This happened to me, and it burnt a small chunk out of the cylinder skirt. Making sure the skirts were sitting flat on the steel work table (which was grounded to the welding machine) seemed to be sufficient to stop the arcing. I did not have to go to the trouble to find a place to clip the ground cable to on the block, or make a special grounding lug to bolt on.

This method has come up before on the forum in 2004 in John E. Smith’s post of 15Jun04; re- his stuck head on his 1949 Flying Squirrel, where I have a follow-up reply. I think it was in the preceding post referenced, wherein incredulity to resistance heating was aired. I am pretty sure I responded to that and outlined the method used. I could not find that specific post, but note the date mentioned of 16Apr04 seems to just predate the oldest post on this forum, so it must be on the old forum prior to implementing registration. There use to be a link to the old forum, as a sort of archives, but I do not see that now.

I hope this clarifies the method that I used. It is not a method for everyone due to equipment or nerve, but it did actually work. Once…


P.S. “metalastic bush”