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TR2/3/3A Iron or aluminum plug in top of head?

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T

TuffTR250

Jedi Warrior
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The original aluminum head plug in the TR4A engine in my TR3 failed and let water leak into the oil. What a mess! With the help of some Triumph club members we got the remnants of the old aluminum plug out (what was left of it) and cleaned the threads in the head. I have bought a new aluminum plug from Moss, however, since I have always heard that it is not good to use aluminum and iron together (dissimilar metals), I have fabricated an iron plug from a 1 inch diameter bolt with SAE 14 threads per inch, per what Moss Tech Support told me is the correct thread for that top plug.

I have two questions:
1) Is it best to use my fabricated iron plug, or the original type aluminum plug? See attached picture of fabricated one.
2) What sealer should I put on the threads of the plug? ( I was thinking of using Permatex Aviation sealant, but not sure that is the best)
Thanks for the help!
Bob
IMG_6609.jpg
 
The iron plug should be fine, I've had heads reworked where they tapped to a pipe thread and put in a cast iron pipe plug. Not sure what sealant is best, I think last time I just used a pipe sealant but it's been a while.
 
What some people have done is chase the hole with a 3/4"-14 (NPT) pipe tap and put in a 3/4" brass or iron pipe plug. Use whatever pipe sealant you like.
 
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