The Stovebolt Site Forums The Shop Area Engine Shop Late 235 Rear main seal question

Hi all,

I have been working through my 235 challenges and decided to buy a used, running 235 of known provenance (meaning, the guy I bought it from bought it from a C40 to put in a truck and now sadly wants to LS swap). The block stampings say it is a 1959 block, from what I can gather. It is a later block for sure, so the stamping makes sense to me. The C40 was supposedly a '62. The part number shows as a C40, so I feel good about
this.

Block: 3764476
Pad behind distributor: F430JC
Behind the starter: D299 so April 29, 1959 I believe

Anyway, before installing the motor, I plan to do some gaskets and make it pretty. One gasket I will do is the rear main, as it has been leaking. I bought a Best Gasket kit when I first started down the road on my 54 motor, then pivoted. The gasket set is RS 543 G. It is for a 1953-1962 235. I assumed it would have all of the right parts, but it does not have the rubber rear main, only the graphite rope seal.

I called Best Gasket and they said the rope is fine, but before using it, I would like to see what this group of experts suggests. So, for a 1959 block, should I just bite the bullet and spend another $50 plus for the rubber seal or will the graphite be OK and work just as well.

Thanks for all of the continuing support on this journey!!

Jeff

IMO, either the rope seal or the rubber seal would work, but in either case, more important is the condition of the sealing surface on the crankshaft. If it's got rust pits on it, it will eat up either seal in short order.

Proper packing and RTV placement per Best Seal instructions are necessary. Shimming and pinning may be required for proper sealing on the crank. I agree on polishing the crank. Always a good idea.

The best fix is also the most difficult- - - -machine the back of the block and the main bearing cap for a full circle lip seal like the one used on the late model Chevy small block V8. National, SKF, and several other brands of seal have a part number that fits. The dimensions are 3.875 shaft diameter, 4.750 outside diameter, and 0.375 seal width. There's also a "speedy sleeve" available that puts a smooth stainless steel surface on the crankshaft hub. The downside is that the engine must be torn down to a bare block before doing any machining.
Jerry

My experience with this seal was to use theBest Gasket rope seal. It is a woven product. The secret for my success on my 216s was to shim all the main bearings for minimum clearance as per specs. For me, the seals did not work until I did this. Both 216s did not leak after that and I still drive one of them to this day.

Hi got the rubber seal. The motor is on a stand. Pulled the rear main and loosened the other mains. The crank bearing surface looks great. I was able to get the seal in.

Out of curiosity I pulled the upper bearing and lower rear main bearings. The crank main journal has some fine lines but looks very good from what I can tell (newbie here). The bearing show a bit more wear. I am guessing that they are .010 0versized. See the pics. I thought size would be stamped not printed but being a newb I learn ever time I step near this motor lol.

What do the other (inner) side of the bearing look like?

Hi the lowers all have some wear. Two have some copper showing. The other two you can see some grit scoring. The crank has some light scoring but the bearings being softer metal are more scored. The crank looks like it would polish. That all said, I am on my third try with this motor (two other duds)…it is supposed to be a runner (Saw it run in the truck from the guy I bought it from) but it needed resealed. I am trying to save money so I have the motor torn down minimally. Pistons are .040. Cam looks great.

Edit here are pics: #2 lower bearing then #4 lower bearing then the same crank journals 2 then 4. 2 is worse than I recalled.

Just my opinion, but if the bearings are already undersized, polishing the crank journals will give you excess oil clearance even if you put in new bearing shells of the same undersize. If the bearings are showing copper, they need to be replaced. And the crank should be reground to the next undersize. That's if you want to get any life out of the repairs.

Yup, this. While the crank doesn’t look real bad, it will take quite some polishing/grinding to get it smooth, and will definitely affect bearing clearance.

One other observation- - - -the thrust face of that crankshaft is showing some noticeable wear. Before you decide to do a regrind, check the end play. While it's possible to weld a thrust flange and regrind it, starting with another, better condition crankshaft might be a better option.
Jerry

That #2 journal does show some roughness on the edge, but that's not the face that takes thrust. That would be the #3 bearing. Notice that the bearing shell in place is the open end style. It looks to me that that roughness happened when the crank was last ground.