Engine Rear main bearing condition?

joekurt · Apr 2, 2023

Hello all. Several questions here. Decided to replace my rear main bearing seal ('76 302 out of a Mustang II). Luckily the engine is still on the engine stand and our new Tremec TKX is not yet attached. So, we rolled it over, pulled the oil pan, and removed the bearing cap. The seal came out relatively easily. Normally the rear bearing cap on these engines has a small pin that keeps the the seal from spinning. Ours is missing.
So missing pin questions - How important is that pin? Can I install a new seal without the pin? If not, is it possible to get a pin and reinstall it? See picture.

Then we noticed the dark coloring on the bearing and what looks like a chip in one corner.
So bearing condition questions - Should we be concerned with the dark coloration? and Is that chip by design to keep the bearing from spinning?

All thoughts, opinions, and suggestions greatly appreciated!
Thanks.

LILCBRA · Apr 2, 2023

I don't have a good answer about the pin. I don't recall there being a pin in the 302 that I rebuilt and used in my car, but it's from a 68 Cougar. It could be slightly different, but I'd guess that it's not and the pin wouldn't be necessary. What I think the hole that's visible in the cap is is for drainage, not a pin - but I could be mistaken.

And as for a missing chunk or dark coloring on the bearing, I don't notice much of anything concerning in the pics you've shared. If memory serves, the bearings that I installed have a slight indentation in that relative location which I assume is part of the manufacturing process. That would be where if guess the bearing was pressed to give it it's locating "key" for the bearing cap and maintain its location. The dark part of it, as far as I can tell, looks to be from normal wear. So as long as the crank journal still looks good, I'd guess that you could get away with just reinstalling the seal and putting it back together.

joekurt · Apr 3, 2023

Thanks LILCBRA! Pretty sure a pin goes in there. I've looked at some YouTube videos on replacing rear main seals and one had a pin, one had a pin that was so high it deformed the seal and the guy ground it down. The third one had no pin. I think Ford's concept there was to keep the seal from spinning. I agree with you. I'm not going to worry about the pin. I was actually more concerned with the discoloration on the bearing, only because I have almost no experience looking at bearings. I rebuilt that engine in 1999, put in fresh bearings, then put about 3,000 miles on it before I garaged it. So those bearings have 3k miles and 30+ years of sitting. Thanks for the input!

LILCBRA · Apr 3, 2023

You're welcome!

2Blue2 · Apr 4, 2023

Pin was to hold old style rope seal in place.
pin makes new style seal unhappy

now which way does that pesky lip go

Engine Rear main bearing condition?

joekurt

Member

LILCBRA

I wish I didn't have all of these balls in the air

joekurt

Member

LILCBRA

I wish I didn't have all of these balls in the air

2Blue2

will be trying this sex one when I can find it

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Engine Rear main bearing condition?

joekurt

Member

LILCBRA

I wish I didn't have all of these balls in the air

joekurt

Member

LILCBRA

I wish I didn't have all of these balls in the air

2Blue2

will be trying this sex one when I can find it

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