I’m about fed up with the set of 3.8 HD8s that I bought for my project 63 coupe quite awhile back. I’ve never seen so many stuck parts. After soaking the front carb in my parts washer for months, I finally got the damper piston out of the body, although ruined, only to find the air bleed screw impossibly stuck (eventually broken by me and with the tip unable to be extracted even by an experienced machinist. I replaced the body with one from a sedan set, and sent the dampers and pistons to Joe Curto, who fixed me up on those.
After finishing the front carb, I went on to the others, only to find the shoe rods for the choke mechanisms firmly stuck in the bodies. - never seen that one before. Does anyone have a trick for getting those loose? I’ve soaked and tapped to no avail. A bit of judicious heat on the rod? I found a new rod on ebay - only $100! Carbs from hell.
Boy what a nightmare. I hope all this was disclosed and you got them for a fair price. What fluid are you soaking it in? I doubt the standard degreaser in a parts washer will do it. It’s probably corroded aluminum. Maybe try one of these methods like a boiling vinegar solution. Don’t just let it stew in vinegar as it can harm it. Rather dunk it for a few minutes then rinse in boiling pure water and try and work it, and repeat till free.
Burlen seems to be out of the shoe rod but maybe they or Joe have a used one. I think if you can get them free they can be reused though. It’s just a brass rod.
Good thought. I did try boiling with the stuck piston to no avail - I probably didn’t use much vinegar. The trick is to get whatever you are using down the shaft. It wouldn’t be that hard to make the part if I had to, but one wouldn’t want to ruin the body. What I paid a number of years ago would be considered a give-away now, so I can’t complain in that regard, but it’s a lesson learned.
Thanks
I guess you could safely bore a small hole into the side of the shaft hole to let vinegar solution in. It would look a little odd but won’t affect the functionality. Last ditch effort maybe.
Fellow lister Alan Dell and I spent a pleasant afternoon a couple of summers back getting two of his choke shoe/rod assemblies unfrozen. Yes, we used a propane torch judiciously, after verifying no fuel leaking from the carb. You need to heat the casting, not the rod. Also PB Blaster during the cool down. Heat/penentrant a couple times, but wipe off the previous application of penetrant before applying heat again. Twisted the shoe back and forth a tiny bit at a time until we got some movement - once it budges it’ll come out. We did this in situ with very few personal injuries and cuss words so it should be a snap on the bench.
Unfortunately, when Al corrodes it produces Aluminum Oxide… the same stuff used to make grinding wheels, sharpening stones, sandpaper etc. Al2O3 is insoluble in water, but is soluble in Ether (starting fluid).
Equally unfortunately, when an SU has reached the point of decay that yours seem to, many of the threads will have become crumbly enough that they need helicoils or welding and redrilling/tapping to restore functionality.
If it’s the steel parts you’re trying to save, cut/drill the Al and chisel it to open the hole (or boil in a caustic solution).
If it’s the Al you’re trying to save, drill the steel bits as far as possible (to reduce mass), then boil the carbs in Alum, which will dissolve the steel without attacking the Al. This will often leave a dark smut on the surface of the Al which can be very difficult to remove.
Some excellent ideas here. I think I will likely end of using all of them. For the old carb body, which I had thought to be junk, I’m going to try the alum bath. I have used alum before in dyeing veneer strips that I use for rosettes and purfling in guitar building, but that is Al acetate. What I think you are referring to must be Potassium aluminum sulphate, which I have not used. I found this on the web:
“Alum in the form of potassium aluminium sulphate in a concentrated bath of hot water is regularly used by jewelers and machinists to dissolve hardened steel drill bits that have broken off in items made of aluminum, copper, brass, gold (any karat) and silver (both sterling and fine). This is because alum does not react chemically to any significant degree with any of these metals, but will corrode steel. When heat is applied to an alum mixture holding a piece of work that has a drill bit stuck in it, if the lost bit is small enough, it can sometimes be dissolved / removed within hours.”
This did not occur to me or my machinist. I found some on Amazon prime for 12 bucks. I’ll report back about whether it rescues the old body. BTW, the threads are fine, just stuck.
Since the rod is brass, I’ll be trying Nick’s suggestion for getting it unstuck, possibly with an extra hole as suggested by Erica. Thank you all very much.
Yes, the Alum used for making pickles is what I use.
It isn’t terribly fast for large bits - I can dissolve a screw out of a watchplate in about 20min, but to get a #10 screw out of a blind hole will take something closer to a day.
Drilling down the center of the screw will make things go faster (a lot faster).
So, tried 5-6 cycles with heat and the pb Blaster, so far not budging, but will let soak a couple days while I’m out of town and try again. How much heat can you put on these castings without catastrophe?
Years ago I took my wire wheels to be trued. The shop had a 55 gallon drum of warm oil that they put the wheels in to soak for a week or so. They claimed it penetrated the threads and allowed the spoked to be adjusted without breakage.
Maybe immersing the carb bodies in a coffee can of oil or diesel for a while would help; it couldn’t hurt.
It’s kind of hard to regulate heat input to a die casting without a thermo crayon but most castings melt at c.550C. Propane/air gets close to 2000C, so no more than five seconds or so at a time, I’d guess. If it’s going to free up it will respond to several heat/cool down cycles and dousing with penetrant. Do it outside if you can. Generates a lot of smoke.
The bodies don’t really have all that many close tolerance fits, but you can distort a bell (bad enough that the piston will rub) just by holding it still against a buffing wheel for long enough.
So, I did get the shoe rod out of the middle carb. Since it didn’t initially respond to the heat treatment process, I came up with something else that shook it loose (see photo). It still took some back and forth, and the threaded end needed a bit of filing from slight expansion at its tip from tapping in spite of a short screw threaded there. I’m currently cooking the other body with the broken screw pieces in the crock pot, and will report later on that.
Unfortunately, the alum trick didn’t work. I’m not sure why, but I suspect that the HD8 carburetor body is not noble enough on the periodic scale to resist degradation in the electrolyte solution. I could see bubbling from the broken steel fasteners, but they did not dissolve over 48 hours, and the casting is now degraded and porous on the surface, especially inside the throat. Since it was junk as it was, no loss, and now I know. I’m sure there are other automobile parts that are amenable to this approach.
Ron, if you can succeed at dismantling the thing you can address pitting issues with Devcon 10610 aluminum epoxy. Not cheap but effective. We used it in industry to refurbish and repair aluminum motor and pump casings. I used it to fill in pitted throats in my HD8s several years ago and after 8000 miles metering 2000 litres of gasoline they’re intact. You can buy the shoe assembly new from the regulars for under $100 or so. If the rod in yours is stuck firm you could always cut it off flush with the casting and drill it out in a drill press.
Glass beads in the cabinet at 30 psi or so will clean up that casting.
