The Stovebolt Site Forums The Shop Area Engine Shop Replacing rear main seal w/o removing engine

I’m needing to replace the rear main seal and oil pump on my ‘54 235.

Are there any special or specific tools needed to replace the seal without dropping the crankshaft? I’ll be using original style rope seal.

Does anybody know of a shop in SE Tennessee that could do it for me as I don’t have a lift and laying under the truck in gravel does not sound like fun.

Sneaky Pete, if you are lucky.

Can you explain “Sneaky Pete”?

It's a seal installation tool sneaky pete

Thanks Wayne!

Best Seal has a replacement seal and tool to pull the seal through but, you do have to drop the crank a quarter inch .
We attempted to do this on my 302 and it leaked 20 times worse than before.

You can’t machine block for the rear main for a lip seal so….

The motor was disassembled, new Best Seal obtained, both block and cap shimmed .0010 and double pinned to keep the seal from spinning. The seal was PACKED in and the end of the crank knurled inward and polished. After everything, there was a noticeable increase in resistance when spinning the crank.

Installed the motor in the truck, then broke my foot which is preventing me to bolt up the trans and run the motor to test.

But I am confident this will help with oil leaking. We will see!

A sheet of plywood makes the gravel ever so much more comfortable.

You will have to drop the crank some (1/4 inch?) to do this job. That involves loosening all the main caps and likely pulling the transmission to allow the crank to drop. Then you can use the Sneaky Pete. Best Gasket may make a two piece rubber lip seal to fit the earlier engines that came with rope-type seals. They are the sole source of those for the later engines. While you're under there with the rear main cap off plastigage the rear main bearing and peel shims as required to get the tight factory clearance on the bearing. That will reduce the amount of oil that can find its way to the seal. Also check the crank surface where the seal rides. If it's rough the seal won't last. Oh and while your'e under there plastigage all the bearings. You may not be able to find new ones but you can shim them if they're not down to the copper. Tapered shim stock must be available somewhere these days.

In the Model A & T days folks used to hang a can on a wire under the clutch housing to catch the oil. Maybe in the Depression they poured it back into the engine, who knows. Definately a hillbilly fix but people were hard up against it in those days. I've just accepted some oil leakage there, just so long as it doesn't wet the clutch.

Tom before you remove and attempt to replace the rear main seal, you can try this:
1. Remove the rear main bearing cap and you may also need to loosen the other caps a bit to let you pull the crank downward a bit
2. Get a windshield wiper blade...the type that uses the stainless steel strip for stiffening the rubber blade
3. Remove the stainless piece and remove the rope seal from the lower cap...very carefully as you may or may not want to re-use it
4. Use the lower cap for a length measurement and cut the stainless steel strip to fit in the bottom of the rope slot from end to end
5. Bevel one end of the stainless strip as you would a knife blade...bevel it about 1/8 to 1/4" or so
6. Insert the little stainless piece you made with the bevel facing the upper rope piece
7. Using a small hammer very carefully tap the stainless piece and force it through the slot (on the back side of the rope seal which you will not remove)
8. This will tighten the seal against the crank by the thickness of the stainless piece and will also cause the rope seal to pooch out on the ends a bit...maybe 1 to 1.5mm. Don't worry about this.
9. Now your upper seal piece will be okay. Tighten the caps if you loosened them.
10. As for the lower rope seal, you could re-use the seal that had been there or you could remove and re-pack it with a new one.

Good luck. I've seen this work several times and it will give you the chance to fix without removing the engine.

PS...the rubber 2 piece seal can be used on the 1956 and newer 235s but I haven't had any luck using those on the earlier ones. Maybe (large maybe) if you could install that seal and shim under it, but the engineer at Fel-Pro (who originally made that seal) told me the block on the early 235s was machined incorrectly and that seal shouldn't be relied on for those early engines. Although I don't know what the problem was.

Tom, in your shoes, I'd sure give Jon's method a try. Others have recommended same and I plan to give the stainless wiper insert a shot soon. That said, you may want to check main and perhaps rod bearing clearances. Main clearances can affect rear seal leakage.

My last efforts along with a ton of good advice from those who know is HERE.

Good Luck,

RonR

If on the off chance you do find you need to remove the engine, I would contact Jerry, (HotRod Lincoln). Jerry has a fixture to machine the block for a one piece rear seal. He is in Delrose TN as well.

Because of the volume of cast iron chips (dust, really) generated by the machining, it's best to do the lip seal conversion with the block stripped down to bare bones, then thoroughly pressure washed afterwards. It's a permanent fix, however!
Jerry

When I rebuilt a late '55 235 many years ago ('73 or so) I used the rope seal. It was difficult to get it mashed into place and have the crank still turn. I believe I squeezed it in a vice and used a hammer handle tapped by other hammers to get it small enough. Ultimately this worked. At the time I did not know about the neoprene seal and it wasn't in the gasket kit. This lasted leak free for many years. Thirty years later when I replaced it with a neoprene one it always leaked some. As it turned out, the leak wasn't the rear main at all but coming from the back of the side cover where I couldn't see it from the outside. I had taken the flywheel off to check that it wasn't coming from the cam plug and saw that it was coming from above the cam. All this after I had replaced the rope seal.

One other thing I will add about the neoprene (not really neoprene but a viton rubber mix I was told by Fel-Pro) is that you need the rear portion of the crank as slick and smooth as it possibly can be. The rope seal is known to harbor acids and moisture (particularly in humid areas like Dallas) and this will chew up that seal tout de suite.

A 3 7/8" "speedy Sleeve" is available that does two things- - - -it gives a super slick stainless steel surface for the seal to ride on, and it also increases the crankshaft hub diameter by a few thousandths to give a tighter fit to the seal- - - -rope or rubber. The lip seal I use can handle up to a .015" oversize shaft diameter because of the garter spring, so I'd highly recommend adding the sleeve to the crankshaft in addition to the lip seal.
Jerry