TR3 Head Aluminum Threaded Plug

["Bill Brewer" <bbrewer@qnet.com>]

     On the upper surface of the TR3 head there is a threaded aluminum plug.
Originally, it was about 1/2 inch thick. Mine had corroded to about the
thickness of a quarter. I am putting a new one. How does one seal it up so
it won't leak? It is a straight thread and not a tapered pipe thread. Should
I use aviation Permatex?
     TIA

     Bill Brewer
     1960 TR3A
     Tehachapi, California