I have a few tired old pot metal distributors, some are badly cracked and some have some promising life left in them. Has anyone found any process to prolong the life of such old potmetal? My older and often wiser brother has suggested maybe soaking the housings in diesel fuel for a while. Any ideas or success stories out there in T Land?
Use them as patterns to have new parts made out of aluminum if that's worth it to you. This has always been a problem with 4 cylinder Chevrolets, which is why the reproduction distributors are cast from aluminum.
Unfortunately zinc castings disintigrate over time. There is little you can do about it.
Ditto what Royce said. The "pot metal" or die cast can be various mixtures but mostly containing Aluminum, Zinc and Copper. The combination if very atomically active and old parts get brittle and self destruct.
Lead was used as a lubricant in the die cast injection mold industry years ago. Depending on how much powdered lead was used in the mold(not every shot into the mold needed repeated lubricating)would determine a century or so later how stable the pot metal mixture would stay.
Royce is right.
Antique phonograph collectors, Lionel train collectors,coin-in-slot device collectors also share your pain and frustration.
It wasn't till late in the '20's that they realized that virtually any lead was fatal to long life of "pot metal" parts. Royce's answer about sums it up.
Same problem with many of my antique radios Ed. All I've been able to do was surround the pot metal with layers of JBWeld. It won't solve the problem - it just delays the inevitable demise of the part. The warped parts I layered nearly 15 years ago are still in the same condition they were then, and work perfectly good now. Maybe they'll outlast me. If your problem is with the housing then yer gonna need lots of JBWeld, but it's really not expensive compared to having to replace the dizzy.
As I understand it pot metal absorbs moister and actually expands over time. Bob Scherzer who posts here from time to time has a foundry and has reproduced some pot metal pieces in aluminum. Seems the old parts that have swelled make good patterns as the pattern has to be slightly larger than the final cast part since castings shrink as they cool and the pot metal swelling and casting shrinkage are about the same. Aluminum is a much better material than pot metal, if you are looking for a long term solution for pot metal it is to replace it with aluminum.
My dad used to cuss pot metal just like I cuss plastic today. After several years, they both get brittle and crack and fall apart.
Seems like everyone's thoughts echo what I have heard to date before. In going on a little tangent, if one was fortunate to have a distributor or another part such as an ignition switch housing that was in excellent shape, is there a way to prolong it? If the penetration of moisture accelerates the swelling of the part, then what is the best way to seal the part to head off the future potential problem?
If you were to keep pot metal parts in a vacuum there will be no oxygen to promote oxidation of the material.
Obviously that is not very convenient. The next best thing would be to powder coat or paint the part to seal it.