Rope or Rubber rear main seal?

-
Nick M.

Nick M.

Well-Known Member
Joined
Aug 28, 2008
Messages
92
Reaction score
0
Location
San Diego CA
76' 360 stock crank and rods, fresh from the machine shop. I removed the original rope seal when i tore this thing down, just wondering what you guys prefer, I had planned on a new rubber seal (fel pro) but i thought i should get some opinions. The crank is grooved at the sealing surface for the rope seal, are non rope seal cranks grooved also? forgive my ignorance, this is my first mopar build.
 
You mean it has the light "screw threads" on the surface that contacts the seal, right? I'm pretty sure all factory Mopar cranks have that, it really doesn't matter. I don't know if you can even get new rope rear main seals now; the rubber ones work fine though.
 
Yes i am refering to the small angled "screw thread" grooves factory cut into the crank. I have used rope seals in the past on some GM stuff with good results but i would expect a modern rubber seal to work better as long as it wont be a problem with the crank grooves.
 
Block is a 76 360 as is the crank.

100_1117.jpg


I use rubber main seals not rope! Ford FE motors used rope seals and when it comes time to change them it is easier to pull the motor out than it is to change the seal in car/truck. You can never get all that crap out of there.
 
I used to be a chebby mech. When they went to rubber, the trick was to stagger the seals , 1/8" out of the top main; not mate them to the block. It has always worked on my mopars, too.
 
On fresh builds where the crank is out of the block there is nothing like a rope seal. It will never leak or seap. But once it's together I've never been good at replacing rope...lol.
 
been using neoprene rear main seals for 30 yrs...

never had one leak yet...
 
moper said:
On fresh builds where the crank is out of the block there is nothing like a rope seal. It will never leak or seap. But once it's together I've never been good at replacing rope...lol.
Click to expand...
Lol, I still have the tools to sneak them out. Not used since 1972.
 
Thanks for the replies, i guess i will just use the rubber seal that came in my gasket set. :-D
 
Like green1 said don't put the seal flush with the block and also the main cap. Rotate it just enough like he said to have the 1/8 inch sticking out of the block and also out of the cap and that way when you put the cap on, the seam where the two pieces meet will be "inside" the cap and block where it can't weep out at the point where the cap and block mate. I had that happen to me even with putting a little sealant where the two pieces mated together. I learned after having to pull it back apart. It wasn't a big leak but oil leaks drive me nuts and I wasn't going to just live with it. So far it's been leak free now for a long time. Now that I've said that, you watch, something else will start leaking! ERRRRRRR!
 
I have had great luck with Felpro rubber rear main seals. I did one on my old 340 didn't leak a drop for years and the new stroker has one too and it is 100% leak free. I did not stagger the seal either. You also need to put a thin film of sealer between the rear main cap and the block or it will leak.
 
You can't stagger the upper and lower half of the rear main seal! The lower seal half has two "side seals" built in to seal the cap to the block.
 
You must log in or register to reply here.
-

Back
Top