I have a spare bottom end, bought for parts needed for my WM21 rebuild. The castings are well-weathered (years of sea air) and the timing cover screws are worn and stuck fast. I've tried heat, sharp tap with a hammer and an impact screwdriver. One out. Any hints before I resort to a man with a big bench drill? The weathered finish on the timing cover would make someone happy, if it could be saved.
How much heat have you tried? I was at a friends workshop recently and he was using a propane powered space heater to heat up a whole Inter Norton engine to remove stuck screws. The engine was almost too hot to touch, I didn't stay for the screw extraction but he said they all came out. If you have gas welding gear try heating the screw heads to red heat with a small nozzle, no.3 or 5 lightweight torch size. This needs great care not to melt the alloy, be very careful indeed. Also not easy, electric weld a short rod to the screw head and grip with Mole wrench to turn. Spark erosion may work if you can find anyone with the gear who is willing to tackle this sort of job. Or just sacrifice the cover if nothing else works.
If you have a TIG-weld you can heat the screw to just about melting point by simply putting the arc to the head of the screw. Will most likely do the trick, works every time for me at least.
As ever, thank you all for sharing your experience and tips. I'll certainly try welding some wire to the screws, rather than opting to drill. And a lot more heat. I'll let y'all know how it goes. Unless I melt the thing into a big blob, obviously.😃
