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Had no response in the Q&A section so I'll try here !
Any tips on installing the rear main seal on a 340 ? I'm getting tired of oil leaks. 3rd time fixing this. I can't tell if it's the rear main or the oil pan gasket that's leaking. It drips off the bell housing. Oil sending unit is dry. Can't see the cam plug. The rubber seal on the rear had a tear about a 1/2" at the top right side when I pulled the pan out. The clutch hasn't started slipping yet. would too much oil preasure cause an oil leak ? 90 psi @ start up and about 50 when hot at idle. I know too much preasure will expand the oil filter or blow it apart.

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Thats a fairly high oil pressure(more than I would
run).... check the crank in the seal area REAL good
I also put a dab of silicone at the edge of the seals
before I place the cap on

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Had no response in the Q&A section so I'll try here !
Any tips on installing the rear main seal on a 340 ? I'm getting tired of oil leaks. 3rd time fixing this. I can't tell if it's the rear main or the oil pan gasket that's leaking. It drips off the bell housing. Oil sending unit is dry. Can't see the cam plug. The rubber seal on the rear had a tear about a 1/2" at the top right side when I pulled the pan out. The clutch hasn't started slipping yet. would too much oil preasure cause an oil leak ? 90 psi @ start up and about 50 when hot at idle. I know too much preasure will expand the oil filter or blow it apart.

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Thats a fairly high oil pressure(more than I would
run).... check the crank in the seal area REAL good
I also put a dab of silicone at the edge of the seals
before I place the cap on

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I took the oil pump out and removed some of the washers I added to bump up the preasure. I primed it in the vice and now the oil guage reads 75 psi cold with 10 w 30. I usually install main seal with a dab of oil on it and slightly stagger it with 1/2" of the seal sticking out of the block then 1/2" of the seal sticking up on the opposite side of the cap. Then dab the ends with silicone along with the corners of the pan. Maybe the oil on the seal is part of the problem ? And I may have torn the rubber oil pan seal on last install. That was my main concern to use oil or silicone when installing main seal ? Thanks Mr P

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Do you stagger the seals so the each end is inside either the cap or block.........move the parting line a few degrees up or down ?
I have always done this with every other motor I have built and had good luck so far.
This is my first small block MoPar , but I planned on doing this too.

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Yes
Thanks

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I had the same problem...is there any chance you have a crankcase pressure problem?

Do you run pan-a-vacs in the headers?

My problem , we figure, was the original engine builder put low tension oil rings in ...and that was part of the crankcase pressurization problem.

I'll find out soon, but I had oil puking out of both ends of my oil pan.

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I don't think it's a crankcase preasure problem. I use a pcv valve on one side and a 3 line breather on the other. Not sure what a pan-a-vacs is ? But nothing is in the headers.

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Had the same problem sometime ago. Staggered the seals and never had a problem again. Chuck

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Also,,I silicone behind/back of the seal and put a little on the ends where they meet together in the housings. The oil you are seeing may be going BEHIND the seal and the seal to crank area not be the actual source of the leak.

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Had the same problem sometime ago. Staggered the seals and never had a problem again. Chuck

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Also,,I silicone behind/back of the seal and put a little on the ends where they meet together in the housings. The oil you are seeing may be going BEHIND the seal and the seal to crank area not be the actual source of the leak.

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Had the same problem sometime ago. Staggered the seals and never had a problem again. Chuck

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Also,,I silicone behind/back of the seal and put a little on the ends where they meet together in the housings. The oil you are seeing may be going BEHIND the seal and the seal to crank area not be the actual source of the leak.

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I think my problem was the rubber oil pan seal. Here is a pucture of how I installed the main seal.

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I'm not a fan of rotating the seal... as you see
in the pic you cut the wings off... thats just another
point for a leak... I put a smear of silicone across
the joint and the wings... I've never had a true
main seal leak but have had a pan gasket leak...
alot of us think its a main seal when really it isnt... JMO

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I think this was my problem. The last kit I pirchased had the tabs seperate from the main seal. Can't remember what company. I didn't cut them off though. I have the new main seal which are the brown seals in this pic. They are Fel-pro #40181. They came with no tabs on them and no tabs in the box.

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In your case you will have to fill the grooves for
the wings with silicone or Right Stuff but leave a
small mound for a contact point.... the reason I
dont like to rotate the seal is the factory spent
MANY man hours to find a way to cut down the warranty
cost issues with the old style(no wings) and they
came up with the wings.... you never seen a factory
seal rotated..... again... JMO.... I had to replace
the pan on my Jeep(rusted out) and I had to cut the
wings off due to the seal was made backwards and on
a 4.0 engine the wings are different sizes... with
silicone at the joints its bone dry and thats been
over a year and half now

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Will the fel-pro black silicone that's in the pic work ok to seal it ?

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It should but make sure the surfaces are DRY from
any oil(oil the crank so it doesnt stick to it and
tear up the joints)