Rear Main Seal Question

[Joe Flanagan]

I'll be installing my crankshaft soon and was looking at the new rear main seal I have. It's the rubber type that comes in two pieces, one that goes into the block and the other that goes into the bearing cap. I notice that the ends are longer than they need to be. They stick out with some excess like the cork end gaskets on the oil pan (which I know you do not cut). Can anyone tell me if these are supposed to be trimmed or if you're just supposed to compress them as you tighten the bearing cap down?

Also, I seem to remember that some guys have used a sealant between the rear main bearing cap and the block. True?

By the way, I have the car all painted (though still partially in pieces) and the camshaft and valve assembly installed in the engine. It shouldn't be long before I'm firing it up again.

[Don Coatney]

Joe;

If I recall correctly you sent me these seals, I trimmed them, and they worked. Not that my car is leak proof as I have several leaks but I do not believe the leaks are revelent to me trimming these seals.

[greg g]

So did you use the mat knive, the x acto, the diagonal nippers, the air grinder? Or just scare em shorter through the use of tool shock and awe. See you had the tooth brush ready just in case.................

[Don Coatney]

So did you use the mat knive, the x acto, the diagonal nippers, the air grinder? Or just scare em shorter through the use of tool shock and awe. See you had the tooth brush ready just in case.................

All of the above:D:D

[bamfordsgarage]

Joe, how much too long do those seal ends appear to be?

My experience with main bearing seals (on Model Ts, mind you) is that they are left long and squished tight when the halves are bolted together. Same holds true for the felt seals between the Model T transmission cover and the rear of the block.

I suspect if the Mopar seals were meant to be shortened before installation, they would have been made shorter in the first place and saved the manufacturer some material cost.

Suggest you try to locate a printed reference one way or another before committing yourself to pre-trimming or not.

[james49ply]

Every rear main I have installed always was a tad langer than the edges, this is to force the inner part of seal against the block and cap to insure a tight seal between them. The seal should have a steel (metal) rod inside the moulded rubber to accomplish that.

[Dodgeb4ya]

Those rear main seals should not be trimmed at all-they crush down when the main cap is tightened.

[Joe Flanagan]

OK, thanks everyone. I suspected that they should not be trimmed but I thought I'd ask. If I had to guess I'd say they're about 3/16 to 1/4 inch too long. I suppose this will compress when I torque the bearing cap down. My manual makes no mention of it, in any case.

Anyone know anything about using a sealant between the rear main bearing cap and the block? Thought I'd seen some mention of that somewhere or read it.

[TodFitch]

OK, thanks everyone. I suspected that they should not be trimmed but I thought I'd ask. If I had to guess I'd say they're about 3/16 to 1/4 inch too long. I suppose this will compress when I torque the bearing cap down. My manual makes no mention of it, in any case.

Anyone know anything about using a sealant between the rear main bearing cap and the block? Thought I'd seen some mention of that somewhere or read it.

I'd be very leery of putting anything between the bearing cap and the block: Your bearing clearances there are in the fractions of a thousandth of an inch and there is no way I can imagine were you could control the thickness of a sealant to that tolerance.

[Joe Flanagan]

That's why I wondered about leaving the seal ends protruding, because of that thousandths-inch clearance issue.

[Don Coatney]

Be it right or wrong the pieces I cut off can be seen in the picture below near the exacto box. I used ProLock to glue the seals in place. As I said I do have leaks but I believe most are coming from my modified oil pan. I add about a half quart of oil every couple thousand miles and I believe this oil usage is from the leaks as I never see any smoke out the exhaust and very little blow by with the engine running and the oil fill cap removed.

[Joe Flanagan]

More than one way to skin a cat, I'm sure. Since my last post, I talked to the guys at Vintage Power Wagons who told me that the gaskets should be left untrimmed and then compressed down when you tighten the bolts on the bearing cap. Don't remember anymore how I did it on my first rebuild.

I was just quoted over $400 for rod and main bearings from VPW. I was shocked. I checked Bernbaum just to compare and he charges $160 for the same items. I have to wonder if the guy wasn't having a senior moment. The maddening thing is I have nearly an entire set of .30 oversize main bearings except for one half that is missing. I just need half of the front main bearing and I have the whole set. I don't know where I got them but they were in a box in my garage.

So how's that for a strange request: One half of the front main bearing at .30 oversize.

[DutchEdwin]

The maddening thing is I have nearly an entire set of .30 oversize main bearings except for one half that is missing. I just need half of the front main bearing and I have the whole set.

Joe,

you might try calling eggy.com. They sell a set as also the parts seperate.

I got my parts from them, all very good.

Good luck.

[Joe Flanagan]

Thanks Edwin. I will check with them.