VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Rear Main Seal on 1941 Chevy Too Tight

I'm in the middle of overhauling my 216 engine in my 1941 Chevy. I just installed the rear main oil seal which is the newer type that Chevy's of the 40s and the Filling Station both sale. It's by GraphTite I believe. It sure is a sticky seal. I installed it exactly the way the instructions suggested. Now, I am having to use a pipe wrench to turn the crank because it's so tight. Anyone else had this trouble? I know it's not the main bearings being too tight. It's definately the seal. My thought is that it'll probably wear into place after I get the motor running. However, it's so tight, I'm unsure if I can even get the motor to turn with the starter.

Any thoughts from anyone?

That is why the main bearings are adjusted prior to installing the seal. The seal will loosen up after a brief running.

I replaced my rear seal twice the winter before last because it was leaking. I didn't solve the problem and had a tired old engine so am having a 41 engine professionally rebuilt. I do not see how the rear seal could possibly cause so much binding that you need a pipe wrench to turn the crank. I would look at the tightness of the connecting rod bearings and the crank bearings. All these parts should be set according to your manual. You may want to do an Advanced Search of our chat site and see what problems others have experienced with rear seals, etc. I have visited the machine shop doing my work on several occasions to monitor the work and I am very glad I am not doing any of the work myself. What looks like a simple job is very complicated if you do not have the know how and the right tools. Just what are you doing to the engine as part of the overhaul? I am using Kanter's Deluxe kit and using insert type rod bearings rather than the babbit bearings. Please keep us informed of your progress.

You are right to assume an engine as tight as you describe will never start. Some of the best pieces of advice I got from my machine shop were that the first 15 minutes of running time on an engine is the most critical in its life, use zinc additive break-in oil, and that cams need zinc in the oil to lubricate them well which is not in popular motor oils anymore. Good luck, Mike

Also oil the seal before assembly.

It's not the connecting rods because they are not installed. I did away with the babbit bearings also and went to rod insert bearings. It's not the main bearings either because I loosened all of them. It's the seal for sure. The old seal was a cloth rope type that would move around easier and was easy to install but yet easy to leak. The new seal is very spongy and is made by GraphTite which Chevs of the 40s sells along with the Filling Station. I'm hoping that over a few days as the seal is compressed that it'll loosen up. I did everything per the instructions including lubricating it with oil. It's just a sticky seal. I am 150% confidient this one won't leak if I can get the crank to turn.

Brandon,

I just completed an overhaul on my 1940 Chev 1/2 ton 216 motor about a month ago. My crankshaft mains and rod journals were in good shape, and were worn about .002" under factory spec, so I installed .002" under-size main bearing inserts. The first thing I did on reassembly, with the cylinder block inverted on my engine stand was to lubricate (with white assembly grease) the main bearing upper halves and the main journals and set the crank into the upper bearings. Next, starting with the #4 bearing, I lubricated the lower bearing half and, using the method described in the Chevrolet shop manual, adjusted the bearing clearance, adding or removing shims, as needed, till a slight resistance to rotation of the crankshaft was felt. This is a bit time-consuming by time you do all four bearings, but is very important to get it right. Just as a check, I checked each bearing with Plasti-gage and found them all to be pretty close to .0015", which is just about right. So the old method of adjusting the main bearings by feeling the resistance to turning of the crankshaft is pretty accurate.

When I finished setting all the mains, with the bearing caps torqued down to 80 ft-lb, I was able to rotate the crank (with a slight amount of resistance) by hand. Next, I removed the bearing caps with shims and the crankshaft, being very careful to keep the shims and caps laid out on a cardboard so that the same shims would get put back with the same bearing caps.

I then installed the rear main seal, per the instructions that came with the seal. I used the seal that comes in the Best Gasket engine overhaul set supplied by The Filling Station. On re-installing the crankshaft, I re-lubricated all the main bearings and journals and the upper and lower seal faces. When I torqued down the rear main cap, I could barely turn the crankshaft using an 18" prybar on the dowel pins in the drive flange of the crankshaft. The additional friction had to be coming from the seal because I know I had the bearing clearance set just right. This worried me no end, as I had some doubts as to whether the starter motor would be able to turn the engine over--and I didn't even have the pistons and rods installed yet. Even if the motor would turn over, it seemed like with that much friction on the seal, it would almost certainly overheat and self-destruct shortly after startup.

Nevertheless, I forged ahead with the assembly. By time I completed the engine assembly, including setting the valve clearance and the timing, I had barred the engine through many revolutions, and noted that after breaking the crank loose, it would turn a little easier, but was still frighteningly tight.


As soon as I landed the engine assembly into the frame and bolted down the motor mounts, I checked to see if the starter motor would turn the engine over, and, though it was straining notably, it did turn over OK, so I proceeded with the installation.

Somehow, I missed the ignition timing and had it way too advanced, so when I turned the engine over on the first attempt to start it, it went about one turn and came to an abrupt halt. A second attempt yielded the same result. On the third attempt, the engine fired and nearly started. On the fourth attempt, the engine started, but I couldn't keep it running. Suspecting the timing was too advanced, I retarded it a bit and tried again. This time I was able to keep it running, but it was not running as smoothly as it should. While it was running, it slowed down and stopped suddenly. By the way it stopped, I thought surely the motor had seized, but another attempt with the starter got the engine running. This time I was able to get to the distributor and retard the timing until the engine was running as smooth as a Swiss watch. I had had it so far advanced, it was amazing that it even fired on the first attempt.

The seal did not self-destruct, and, in fact, remained drip-tight for about the first 800 miles. Now, after 1,000 miles, after coming in from the road, it will drip maybe one or two drops over a 24 hour period, which I think is pretty good for this type seal. It's interesting that my 37 pickup, which doesn't have a rear seal, doesn't leak at all. However, the rear bearing is still nice and tight, and as it wears, I expect I'll start seeing some leakage.

The bottom line is, the new rear seal on my 40 was so tight I was worried about it the whole time till I got the engine running and found out it was OK. I hope you have as good a success with yours as I did with mine.

Mark

The graphite type rope seals do need to be tight initially. They free up too quickly and I have never seen 1 "burnt", Graphite is a lubricant in itself.
Tony

I've still got problems! After torquing the main bearing caps down, I can't even turn the crank with a pipe wrench. I've checked the bearings and they are not the problem. The remain main rope seal is too tight. Does anyone have any ideas?

Check in your workshop manual and see if there is a tool for setting up the sizing of the rear main rope seal.I've got a 1940 Olds w/shop manual,and it shows a tool that has 2 diameters machined on it,as well as a rod that you hold.The larger diameter is the parent bore of the block and rear main cap when bolted down.The smaller diameter is the sizing diameter for the rope seal.Before you bolt the cap to the block,you remove the rear main bearings,place the rope seal into its grooves,the replace the main bearing cap,and torque it down.As you do this,the diameter that the rope seal sits on compresses the rope seal to its initial start up firm,not too tight running fit.
Afterwards,unbolt the rear main cap,replace the bearings,oil them up as well as the rope seal,and it should turn over much easier.If you want,I can email you a shot of the Olds tool in question which may give you an idea of how to get one made.

Cheers.

CJP,

There's nothing in my 41 Chevy shop manual that talks about a special tool. However, I understand what you are talking about and it makes since.

I'm planning to call the gasket company tomorrow to see if they have suggestions. It came from Best Gaskets.

Do you need to trim the ends of the seal?

Once the rope seal is fitted with the tool,the ends should be trimmed just flush the both the block and the bearing cap.When you go to install the cap,just put a thin smear of a non hardening sealant,eg:Permatex Aviation Sealant No.3 or something similar,on the ends of the rope seal in the block & cap and torque the cap bolts to the correct setting.
In the '40 Olds workshop manual,it says to leave the ends of the rope seal just proud of the block & cap by about 0.030",then torque the cap down.If I could figure out how to post a picture I'd put it up,but if someone wants a picture,just email me,and I'll send it on.

The seal is always a little longer than needed and must be trimmed. It would be pretty tricky to put sealant between the cap and the block with multiple shims in between.

When you get the problem figured out, I hope you'll share it with the rest of us.
Thanks,
Charlie

It's not rocket science really to put sealant on the cut ends of the rope seal,just smear a small amount on before putting the shims in place.The early Falcons I owned years ago had exactly the same type of rope type rear main bearing seal,and that's what I did,and never had a leaky rear main bearing.And,they were pressure fed too,running around the 40-50 psi mark.

I really enjoy reading this forum and appreciate the feedback and appreciate learning what others are working on. My question in my post was, has anyone had any problems with a rear main oil rope seal being too tight? I got one or two replies that offered good advice. However, how did my post get to "how to seal it?" Or how to set my bearings?

As I said in my post, the bearings are fine,the rods aren't even installed. The rope seal is too tight.

I spoke to Best Gaskets today and they were more that ready to help me. They are sending me two new seals that are two different sizes to see if that could help me. They further want me to keep in touch with them to make sure my problem gets taken care of.

Thanks to those of you that offered excellent advice. To the rest of you, I suppose I appreciate the extra info I didn't ask about:)

The seal I used was from Best Gaskets. For those of you that are unfamiliar, it comes with the rope seals, a razor knife to cut the seal, a wooden piece to press in the seal and to aid in cutting, and a gauge to aid in cutting the seal to the proper height. The instructions are very detailed and easy to follow. The seal is not hard to install. The Filling Station and Chevy's of the 40's both carry this seal.