20-07-2021, 09:44 AM
(This post was last modified: 22-07-2021, 01:45 PM by Tony Griffiths.)
(20-07-2021, 08:13 AM)JonE Wrote: others have suggested a 1/2 BSP tap, so perhaps that is sensible thankyou - even with a brass plumbers plug.
I just wondered what the water pressure retention was in comparison with silicone/epoxy/jbweld strength? Others had mentioned putting core plugs in with a touch of epoxy anyway.
The cooling system on a Seven is not pressurised, it's a simple thermo-syphon system. If the core plug hole is thoroughly cleaned out - especially down into the corner of the circle - then both hole and core plug cleaned with alcohol and assembled with JB-Weld or similar it should be OK. Best to let the glue go off overnight before starting the engine.
An alternative, if you have a lathe, is to turn up your own from bronze or brass. They should be a tight fit and sealed with JB-Weld or, as original on early heads (until 1930?), hammered in and peened over. The snag with any "permanent" fitting like this is that, if the water is allowed to freeze, it cannot, like the pressed-steel type, push then about and so prevent the head from being cracked.