29-08-2020, 08:03 PM (This post was last modified: 29-08-2020, 08:04 PM by Tony Griffiths.)
Just had a couple of cylinder head core plugs start to leak badly which, considering they looked to be original, is hardly surprising. Here's what one looked like - wafer-thin and almost rusted through - against a new example. Of course, the replacements I had were too large, but earlier I'd been looking at a cylinder head where somebody had made their own, as brass plugs, rather crudely bashed-in. So, nothing to lose, I fired up the lathe and made a couple myself. Quite tricky to get the diameter right, but with a bit of fiddling - by putting the discs in the freezer for a couple of hours and running the engine to heat the head - the Goldilocks moment was achieved and both were driven in good and tight.
The tricky part is turning thin discs in the lathe from sheet (other than parting off from solid). What was your technique? Can be dished by hammering into a hollow or hole in a block of wood .
(29-08-2020, 08:51 PM)Bob Culver Wrote: The tricky part is turning thin discs in the lathe from sheet (other than parting off from solid). What was your technique? Can be dished by hammering into a hollow or hole in a block of wood .
I tried that some time ago, turning blanks from a steel bar, but it was very difficult to get them right - and dishing them into a turned hollow was not successful. The brass ones I made had vertical sides with flat tops and bottoms - but made to be a very tight fit, assembled with a smear of Araldite and driven into place with a hammer and punch. Having made one a firm sliding fit as a trial, the next was made 0.005" oversize, frozen for a couple of hours and fitted to a hot cylinder head. The brass core plugs in the spare head that I examined had material peened over the edge of the hole - and so appear to have been made with either a narrow top-hat section or just surplus material sticking up above the level of the head.
Easier method - Cut off a square of flat metal, correct thickness. Trim off corners to 45degrees. Araldite onto end of a bar which has been faced off in the lathe and just smaller than required diameter. Turn to size plus a few thou" . Remove disc from bar - heat ?? Find/ make a washer 1/8" thick with a hole just a bit smaller than the disk. Open your vice jaws so you can get Washer, Disc,Ball pin hammer in-between the jaws and tighten to dome the disc. You should now have your Welch Plug.
30-08-2020, 11:31 AM (This post was last modified: 30-08-2020, 11:48 AM by Tony Griffiths.)
(30-08-2020, 09:12 AM)Steve Jones Wrote: Even easier method. Simply buy replacements from one of our suppliers.
Steve
The obvious thing to do - and a wonderful solution - - if they were not too large for my cylinder head. That's why ones had to be made.....
(30-08-2020, 08:05 AM)bob46320 Wrote: Easier method - Cut off a square of flat metal, correct thickness. Trim off corners to 45degrees. Araldite onto end of a bar which has been faced off in the lathe and just smaller than required diameter. Turn to size plus a few thou" . Remove disc from bar - heat ?? Find/ make a washer 1/8" thick with a hole just a bit smaller than the disk. Open your vice jaws so you can get Washer, Disc,Ball pin hammer in-between the jaws and tighten to dome the disc. You should now have your Welch Plug.
As ever, great ideas from the forum. Many thanks, Bob.
(30-08-2020, 10:55 AM)Duncan Grimmond Wrote: Are you implying that Austin owners should put their hands into their pockets? Shame on you!
While not in the DW class of being able to forge a new con-rod from a 56lb weight scrounged from a coal merchant's lorry, it is rather fun - and satisfying if it works - to have a go oneself at these little tasks.
My special has an old sixpenny piece in one of the cylinder head core plugs, its been there since I bought the car 12 years ago, the machine shop who skimmed the head even took pictures for their rouges gallery.
(30-08-2020, 06:32 PM)john deacon Wrote: My special has an old sixpenny piece in one of the cylinder head core plugs, its been there since I bought the car 12 years ago, the machine shop who skimmed the head even took pictures for their rouges gallery.
I knew that there was a coin that could be made to do the job - I just could not remember what it was.
