The last few new TR3B MK ll heads (TR4A) that I obtained directly from the CA
factory depot had the top of the plug peened around the plug OD; clearly a
factory modification.
A trackside fix is to drill and tap the plug, say for half inch NC and put a
set screw through a flat washer large enough to cover the plug into the new
threads. The pulling force on the plug also helps to seal the threads; we put
sealer on all items.
I only had problems once with a head that had been heated to weld.
Hardy
P.S. if anyone knows of Triumph things to do in London, Ellie and I will have
two short visits
there soon. Please reply Off List, thank you.
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