2 part Rear Main keeps blowing

[Faster Eddie]

So, we rebuilt my original 72 302 block using the same crankshaft. Other than that, everything is new. Fired it up and had oil leak coming out of the bell housing.

Have replaced the rear main (2 piece) a couple times now. Seems to be the lower half that gives out. Have used the black $8.00 seal.

Next steps: stick a feeler gauge in the crank to see if I have too much play. Buy the $26 high performance (brown) 2 piece seal and shove that in with some anaerobic sealant.

Thought about speedy sleeve but sounds like you can't use them with a 2 part seal.

There's an engine close by with a 1980 lower end rebuilt 2000 miles ago.

Question: can or should I take all my nice new stuff out of my 302 and drop it all into this new (old) 1980 block?

Should I use the crank, flywheel and balancer from the 1980 or use my current crank, f-wheel and balancer?

Wide open to help. Thanks guys!!

 

[BRONCROB]

Do you have your pcv system connected.You may be building pressure without it??

 

[Faster Eddie]

Yup PCV all dialed in.

 

[70_Steve]

If it's the original 302 that had a rope seal, there is a pin in the bearing cap that kept the rope seal from spinning. You need to remove that pin or the 2 piece seal won't sit down in the bearing cap.

 

[Faster Eddie]

My current block was a reman crate engine back in 95. Had the cheap 2 part seal in it when we redid it. So no rope seal. It's crazy cause mic'ed everything and thought it looked fine. Really appreciate the help guys

 

[Broncobowsher]

Reseal the intake. Back of the valley gives out and drools down, looks like a rear main.

 

[half cab]

My current block was a reman crate engine back in 95. Had the cheap 2 part seal in it when we redid it. So no rope seal. It's crazy cause mic'ed everything and thought it looked fine. Really appreciate the help guys

original 72 302 block

???^^^^..I confused

 

[Faster Eddie]

The block is a 1972 that came in a crate motor purchased in 1995

 

[Faster Eddie]

Any hope that the the brown (High Performance) gasket will do better than the black rubber on?

 

[blubuckaroo]

Have you got this book? http://www.amazon.com/Rebuild-Small-Block-Ford-Engines-Monroe/dp/B00DEKLU0M
The anaerobic sealant isn't used the shove in with the seal. In fact no sealant should be used between the seal and block/main cap. If you do, you probably won't get the seal out next time. Anaerobic sealant is the correct sealant between the rear main cap and the block. It is applied to the space on both sides of the main cap between the seal and the edge of the cap. If there is no sealant applied there, the oil will wick right out from between the block and rear main cap. Anaerobic is the right sealant for that. Don't use RTV. Before applying the sealant though, clean the surfaces "oil free with lacquer thinner, acetone, or Chemtool

 

[DJs74]

Any hope that the the brown (High Performance) gasket will do better than the black rubber on?

The difference between the "black" & "brown" seals will be the material not necessarily the seal design. The black is Nitrile (Buna N) and the brown is Viton (Flurocarbon). Viton is a superior seal material but is generally used due to extreme temperature applications and is a great material for wear. If your current seal is leaking due to extreme heat, then the brown seal might be worth trying but the normal black Nitrile seal should work fine if all the geometry (seal gland, etc) is OK

When you are installing the 2 piece seal, where are you locating the seal seam (the split) with relation to the block? For example, if you are standing in the rear of the engine sighting straight down the crankshaft, the horizontal block plane (crankshaft horizontal centerline) will be located @ 9 & 3 o'clock - if you also locate the seam of the seal at 9 & 3 o'clock, then you are kind of creating a straight shot leak path and not creating a path of resistance for the oil. I always install the seal so that it is about 1/8" recessed down into the block on one side which will cause it to be about 1/8" protruding on the opposite side and apply RTV to both ends of the 2 piece seal to create a continuous 1 piece seal. The idea is that you don't want the seam of the seal exactly in line with the crank / block / main cap centerline horizontal surface.

DJs74

 

[Faster Eddie]

Don't have the book. Been working with a buddy who has years of experience. This is all great info. Thanks so much!

 

[fablife]

after changing a rear main seal 3 times on a customers rig, and still getting a leak, finally decided to pull the motor, he didn't put in a plug in the back of the motor when he installed it... leak fixed.. I hope yours is easier, good luck, JD

 

[half cab]

First time I didn't file the block enough n barely shaved the top seal! filed the block more staggered the seal good to go,but the pan seal went in wonky on both ends so pulled pan back out and RTVed each end of the one piece pan gasket n now it's good to go.

 

[Faster Eddie]

Thank you webmaster for taking that post down from Grumpy Stilstkin! I'm not stupid or dumb, I'm busy with a big job, 2 young kids, a wife and an old Bronco. I come on here because it's full of people who are passionate about Broncos and are (usually) willing to share their knowledge and foster the enthusiasm we all have for this hobby. I'm sure everyone on here has had to do over something in their rig, even if they DO have "the book" and can read.

Sorry for being a noob, but don't waste your time criticizing me, waste your time getting a life.

 

[Faster Eddie]

And thanks to everyone for the help!

 

[70_Steve]

I'm sure everyone on here has had to do over something in their rig, even if they DO have "the book" and can read.

I have come to accept that I can't do anything on my Bronco unless I do it three times...

 

[Faster Eddie]

Roger that!

 

[half cab]

I have come to accept that I can't do anything on my Bronco unless I do it three times...

Normal thing here plus Murphy's Law!!

 

[Faster Eddie]

How much play should the crank have back there. If I stick a feeler gauge while trying to move it up n down, what do you say 2/1000?