The Stovebolt Site Forums The Shop Area Engine Shop Rear main seal

Having issues installing rope seal in 1962 C20 235 engine. Engine
Locks up when rear main is tightened. Worried about starting after finished re_building.

Did you lubricate the seal surface? I do that when I install one.

Are you sure that it is the rear main seal? Try loosening the bearing caps one at a time to see if the crank will turn. If the binding is happening at one of the two mid caps, check to see if they are installed in the correct direction. The front mid cap has an F in the casting indicating the side that has to go toward the front and the rear mid cap has an R in the casting indicating the side that has to go toward the rear. The F and the R aren't always obvious, but they are there if you look closely. The caps will fit either way but have to be installed with the correct orientation.

Reversing one or both of the mid caps can create the same symptom even if you check everything with Plastigauge first. Everything looks great, so you put in the rear main seal and torque down the mains, then you scratch your head wondering why the crank won't turn and blame the rope seal.

How do I know about this? Even with knowing better and careful labeling, I somehow reversed the rear mid cap on a 235 rebuild about a year and a half ago. The good news is that the binding crank alerted me to the issue, so it was easily corrected without any problems.

Matt

Thanks for the suggestions. I have the other 3 mains torqued and the engine turns freely. I plastiguaged all mains without the rope seal, and had .002 clearance. I did tap the seal with a ball-peen hammer to shape the seal, and coated the seal with white grease and oil before installation. I am being told locally that I have no choice but to contunue with the rebuild, and have faith that I can get it started, maybe with a pull. I was hoping I could find a rubber seal or another option. Appreciate any other ideas.

A 62 motor should be machined for the neoprene seal. After you have confirmed that the bearings are not causing the binding problem, get a neoprene seal and install that. They are getting a little hard to come by these days but see if you can find one. The early 55 and prior motors were not machined for a neoprene seal and if you install one, they will physically fit but will sink deeper into the block and cap so will leak. So you cant use a neoprene on the earlier motors. The later motors, starting in 56 for the passenger cars, and I am assuming for the trucks also but you never know, were machined for the better neoprene seal. I actually don't know the answer to this question but I don't know weather you can install a rope seal into a rear main cap that is machined for the neoprene seal. My gut tells me yes but I really have never looked at that issue because I avoid those rope seals like the plague.

The other thing about the rope seals that are supplied today is that they are not like the seal of old. The original seals contained asbestos and the new seals contain fiberglass. The older seals worked better. So if you have to use a rope seal, or you insist on using a rope seal, see if you can find one that is 20 years or older.

Best or Felpro Neoprene is 4519S, CR, McCord, Victor, and others also made them.

If you have a neoprene seal that is leaking, try using the Barr's rear main seal leak stop. It is not like the pellets from years ago for the radiator leak stop. It is a clear liquid that goes in with the oil and swells the seal. I had the neoprene seal on my 261 leak almost from breakin. Used that stuff and it stopped the leaking.

I just finished a rear main on a 56 motor and used the Best neoprene seal. Very easy install in the chassis.No more leak gone.

Thanks for the suggestions and ideas. I will continue to try and find a neoprene seal. If anyone has a suggestion where I may look for one, I would appreciate it a bunch.

John Paul, I tried to send you a PM but can't because you don't have enough posts yet. I have an extra Best 4519S neoprene seal. Send me a PM if interested.

Matt

Here's the permanent solution- - - - - -a full circle lip seal- - - -but you need to get the back of the block and the rear main bearing cap machined to accept it.

http://mlineseals.com/oil-seal/38691/

Jerry

John Paul, I disagree with the local advice of moving forward on the build with a locked up crank. That's not what I would do.

If you have the crank snout tapped, use a socket and a breaker bar to turn the crank. If you can't get it to turn, something is wrong. If you didn't tap the snout, screw a couple bolts into the flywheel flange opposite each other. You'll use two of the six threaded holes on the flange. Leave enough of the bolts sticking out to catch a pry par. Use that to turn the crank. Once again, if the crank won't turn, something is wrong.

The problem could simply be that the rope gasket is binding too tight and the crank just needs a little help to start turning the first time.

If you can't get the crank to turn using one of these techniques, your starter motor will not have the torque to turn the engine over.

Matt

I thought 1963 6cyl engines had went to the neopreme rear seal .

Tim

The better play here, at least in my opinion, is to redo the process. Remove the main caps (mark them for placement and direction because if the middle two caps get turned around, plays all kinds of havoc with the bearings. I mark my middle caps with two and three divots respectively, on the forward part of the cap to signify no. 2 cap front, and no. 3 cap front).

Remove the crank and the rope seal. Inspect the upper bearing shells for any obvious signs of squashing, jamming, rubbing. Same for the bearings in the caps. If they look good, light oil on the upper bearings and reinstall the crank. Rotate the crank. It should rotate relatively easily but not you push on a counterweight and it spins like a Ferris wheel.. Wipe the journal and clean for a nice dry surface. Lay in a little plastiguage. Wipe and clean the lower bearing shells that are in the caps, then Very light lube on the lower bearing shells, the lighter the better, think sewing machine oil. Install the caps and torque to specification. Remove the caps and confirm that the clearances are what they should be, .001-.003 with .015 as really good, and a little variation as good. Outside of those values, some corrective action will need to be taken, shims for the early motors if too tight, otherwise remachining the crank for example.

If the clearances come up to spec then wipe off the plasticguage and the bearing shell, and lube the lower bearing shell with fresh oil, 30 wt. or so, install the caps, torque to spec and then gently rotate the crank. Should be able to rotate with a little more force. Should not be any binding or binding spots as you rotate. If rotating and no binding, then dissemble the caps, lift the crank out, wipe the bearings clean, lube with fresh lube or assembly lube (I use lubrimatic assembly lube but any good brand will do the job) install the neoprene seal, little offset on the seal, I usually will put a tiny little dab of of sealant on the ends of the seal (I am not particular here, I have used anaerobic, silicone with good results), little swipe of lube on the seal so that you are not doing a dry initial rotation that can tear up the seal, and install the crank. Clean the lower bearings again, assembly lube, install the lower mail seal in the lower rear cap, little swip of assembly lube on the seal and install the caps and torque down. You should still be able to rotate the crank, but with more force. If so, you are in pretty good shape.

Found a 2 piece neoprene seal from Best Gasket. Taking to machine shop to see if the crank machining is accurate enough to seal. Thanks for all the posts, they really help. Will post after machine shop visit.

Outstanding!