Re: Oil pan plug - striped threads.
Reply #60 –
The drain plug hole in my M11 was had almost no threads. I tapped the drain hole to 1 1/8 by 12tpi and obtained perfect threads, so installed a 1 1/8 Fumoto valve with a nipple. Now the aluminum threads are good for life because there is no need to ever remove the Fumoto valve. The differential sits lower than the bottom of the nipple so the only way to break the valve is to back over something.
The one concern I had about the drastic tpi change (from 18 to 12) was the strength of the threads. I researched engineering papers on thread strength and found that in aluminum, 12 tpi is stronger than 18 tpi.
I have available for sale: M26 x 1.5 tap (1.0236" by 17tpi) and M26 x 1.5 Fumoto drain valve (T207N) which would work for a M11 pan with most of the threads. I also have for sale taps for 1 1/8 x 12.