MTFCA Forum

Can someone help with the size and location to redrill the 4 th main oil hole, measurement from shoulder would be good. Trying to finish an engine my Dad built for me before he passed away. I can’t see any trace of the hole in the shell he had re babbited. Thanks

The hole is in the middle of the collar, about 3/8" with an oil cut forward & aft to lube a larger surface of the shaft. (but short about 1/2" from the output shaft end)

I also caution you that your indicator in not in the correct place for centering.
Only the narrow machined area next to the flange face is correct for perfect centering.

Thanks for your prompt reply, yes I did indicate the flat land next to the mounting flange. I had read that in another post. Appreciate the help.

Seen a lot of 4th mains but never an oil cut. I don't think it's necessary but it's not a bad idea. Don't believe they came that way from the factory tho.

Jig boring the 4th main http://www.mtfca.com/discus/messages/25 ... 1356153477 from Lang's part specs

TRDxB2 wrote: ↑

Wed Jan 07, 2026 11:57 pm

Jig boring the 4th main http://www.mtfca.com/discus/messages/25 ... 1356153477
holll.png

from Lang's part specs
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I disagree with the clearance specs as provided. Way too loose.
4-6 will pass a lot of oil into the U-joint especially if you are using a transmission screen.
.0015-.002 is what I fit to in this part with babbit, same as for rods & mains.