Rear main seal leak sbc

[Therriaultper]

Having a problem with a 327 small journal cranks that I can stop leaking oil out of the seal ! The crank is at 2.430 because it have bin polished at the surface. I am running a felpro blue seal and install two of them all ready . Is there a seal out there that is tighter or any ideas that could help me thanks

[rebelrouser]

Not sure if they make one for a small journal crank, but yes there is one for a 350 sized journal. It has shim stock that you use to make sure the seal fits tight, it is designed for cranks that have been turned to small in the seal area.

These guys make the best rear seals, both rope and rubber I have used https://bestgasket.com/rear-main-seals/ give them a call. I don't even try to get the rope seals in the gasket set to work anymore I just buy one from best.

[cgarb]

Back in the day before they made a line bore 400 rear main seal I heard about people putting shims behind the seal to take up the space. Maybe you could try that. A piece of zip tie might work pretty well in that spot and they are plentiful in most shops.

[pdq67]

Did you offset the seal ends like a 1/4"? I always do.

And I also put a small daub of good old Indianhead on each end. Not much, don't want to make a mess sorta deal.

pdq67

[jred]

I've had problems with both a big block with a 1 piece rear seal and a 327 s/j in a 65 corvette,, the b/b was line honed and I did it,, the customer assembled the engine and when he torqued down the crank would bind up but would turn over real good with the rear main cap off,, we finally pulled the crank and checked line bore sizing the bearing housings were right were we put them but the rear cap where the seal goes was oval
right on size at the parting lines but .006/ .007 tight in line with oil pump,, and it was pushing the seal tight against the crank... The 327 small block was actually in a running car and you could see were the crank had flatten out the seal it too had been line honed by myself and I usually only cut .003 to .005 off the caps except when the cap surface doesn't clean up,, both caps were set up on the vertical mill and I used a boring head and centered the caps and bored the holes round again no more leaks,, Back in the 70's when I first stated in a machine shop I was lucky to work in a speed shop,, we were running 406 s/b we had 1 line honed
by a different shop and they cut the rear cap like you have to do on a 400 we used a stock seal and ran a cut off zip tie behind the non line bore seal,,

[enigma57]

What oil are you running in this engine? Have a friend who was ready to pull engine for 3rd time with rear main seal leaking. Recommended he try a different oil and that solved the problem.

HB

[Therriaultper]

The oil I am using is drive br30 an a melling 55a pump . It don’t leak at around 1500 rpms an 60 psi ! But when you run it up to 3 or 4000 it starts to drip oil and I didnt off set the seal !

[enigma57]

That's a good break-in oil. Should be no problem there. I suppose its just a matter of checking the details...... Lip of rear main seal towards front of engine, etc.

Some offset the seal parting lines. Others do not. I have done it both ways and have not had a problem. I do like to put a small bit of RTV on the parting lines of the seal. And I wipe a small amount of Lubriplate #105 pre-assembly lube on the crank journal where the seal will sit to prevent a dry start. Just as insurance. And let the RTV set up for 24 hours or more before cranking engine. No problems so far.

Good luck,

Harry

[turbo camino]

I have always used RTV on the cap surface, but not on the seal ends themselves. Just a tiny amount like what's left over after you wipe it off with your finger.

[Geoff2]

If it only drips at higher rpms, you probably have excessive blow by. The gas is looking for an escape route....

[enigma57]

Might look at crankcase ventilation & windage tray as well.

HB

[jred]

after break in we used 10w30 as 30w straight is hard to find around here ,,I also have used the seal off set and in line with the parting line of the block doesn't seem to make any difference ,, but also put sealer on the back side and at the ends of the of the seal,, I saw some were that people were having oil leaks at rear main cap so I use a small dab on the flat side of the cap were it meets the block and at the champers were the cap meets the register ..