I am going to be replacing the rear main seal this weekend. I have checked the repair manual and don't see any spec for the torque of the rear main bearing cap. Is there a spec on this? The engine is a 1948 216". Any help on this would be appreciated. If I don't hear anything then I will check to see what they are before I loosen them. Thanks for your help!

My shop manual says 100-110 pounds.

When reinstalling the main bearing cap do byou just torque it down and go with that or do you use plastigauge to measure for clearance? If so what is the clearance supposed to be?

You don't have to check the clearance before you tighten the bolts...BUT...it is a good idea to get the clearance as "tight" as possible to cut down on the rear main leakage.
The desired clearance is around .001".
When using the plastigage with the engine in the car (up-right) it is necessary to support the weight of the crankshaft so the load of the crankshaft is not laying on the bearing (and Plastigage).

Thanks Gene! I just got the pan off and there is a silver gray paste like stuff built up around the drain plug. I am assuming this is normal bearing wear etc ( I hope). I have pictures but not sure how to post them. Any help with the posting of pictures or the silver gray paste would be appreciated! Thanks Again!!

The white/gray paste was lead from leaded gas. Was common to see years ago.
If there is a question you can send pictures to me.....chevgene@msn.com

Thanks again I will email you some pictures it will come from Jeff@selectwindowfilms.com

That dark gray/black is sludge came from the normal sludge mixing with the black carbon in the oil.
Good you CAUGHT THE DIRTY SCREEN BEFORE IT PLUGGED-UP COMPLETELY.
If that was my engne I would change oil again in a few hundred miles and use 10W-30 oil.
Remember when you install the pan the side corks go up first (I use grease to hold them in place) and the end corks go last. To curve the end corks (if they are straight) tape them to a soda can for a day.

Yes I am happy to have caught the screen as well. Thanks for the tips on the oil pan gaskets. I saw your previous post on this subject. I just removed the rear main cap to replace the lower rope seal and found that the lower rope was partially tucked into the upper channel and stuck there when I removed the cap. After getting the cap down and out of the way I pulled the rope seal down and probably 1/4" or so was tucked into the upper channel. I can not see the top part of the rope seal on this side. The drivers side the top rope seal is partially hanging out about 1/8" probably. I am wondering if the rope spun in the channel for some reason. There was also a thin foil like shim under the passenger side of the main cap? Is that normal? I'm not sure what it is. I checked torque of the main cap bolts before removing them by setting my torque wrench to 100 lbs. they were a little loose probably around 90 lbs I would guess. Not sure if this was the problem. Now I am also wondering if I should try to snake the top half of the rope seal out. I wasn't planning on it but not sure now. One last note, the rope for the bottom half of the seal seems like it is way short of filling the channel. It is about 1" short of reaching the top edge of the cap. Any guidance on this would be great!

What kind of a rear main seal are you using as they are usually too long and have to be cut off?
I would consider compacting the top half of the rope seal by using a tool to stuff it tighter and then take a piece of seal to stuff in behind it to close the gap.
Shim under the cap....The shims were used between the cap and block for adjustment purposes. When new there were four shims on each side. Two were copper (.002" thick) two were silver (.001" thick)....to reduce the clearance shims were removed.
Before I would do any thing with the seal I would check the bearing clearance with Plastigage.

Will check the bearing with plastigage before proceeding with the replacement of the rope rear main seal. The old rope seal is the one that is too short. By the looks of it I had about 2" gap between the ends of the old rope seal. Not sure why or how that happened. That is why I think I am going to try and sneak the rope seal out and snake the new one in. The new rope seals are plenty long and will need to be trimmed. I thought about packing new mateial against the old seal but thought if it doesn't work I have to take it all apart again. I have heard people have pretty good luck threading a new top seal in over the crank with the Chinese finger clamp snake tool. If anyone has any reason they would not try this and would rather pack the old short top main rope please speak now before I have the old one out and am committed to replacing it one way or another.

The problem with pulling through a new rope seal is that the seal is stretched too thin when it is installed. There again would make it too long and pack the excess into the grove to make it expand.

So I should just take a wood dowel and poke part of the new seal up against the short old seal? Then install the lower rope as normal? I assume this would work but it seems like it would likely leak where I pack the new seal in or around the existing top seal since it has been leaking really bad about 2 quarts every 150 miles. My thought was that having a new seal in would be better. I was told that if I turn the engine by hand with the spark plugs out I could roll the old one out while pulling with a cork screw in the end of the old seal and then pull and turn the motor by hand to feed the new seal in so I am not pulling so hard as to stretch the seal. I have never done it that way so I don't really know how well it works. But I would like to have a full seal in place rather than a packed part of the seal and a new piece on the bottom. Have you done the seal pull around the top of the crank as well as the packing procedure? I might have to sleep on this one. I was going to try and get it in tonight but may wait till morning and think it over.

What do you think of using the old lower rope seal to pack against the old top seal? The one that came out of the cap is already oil soaked and the shape of the groove so I should be able to pack it pretty tight against the old upper seal. If I take the new felpro rope it is not stiff enough to really pack smoothly into the groove of the upper seal. Not sure if this would work or if it is recommended. Let me know your thoughts. I am going to try either way in the morning. Thanks!

The last Oldsmobile 307 engines still used the rope type seal. Cutting off part of the old lower seal and packing it against the top seal was their recommendation in the shop manual.

Thanks Gene I am going to give that a try. How tightly do you pack the old seal against the top seal? I would imagine pretty tightly. Do I use a wood dowel or what to do the packing?

As tight as you can pack it within reason. Wood is good as it will not scratch the seal surface. Also make sure the surface on the crank that the seal rides on is smooth and shiney. Often it tends to rust.

I went through all this with the rear seal a year or so ago. I could`nt see how the upper rope could easily be removed unless the crank was dropped some . Mine was in there tight . I used the lower seal and packed the upper . When the seal material is cut it falls apart. Good luck at this stage . I cut 1/4 inch pieces and used the best to pack up in the upper seal. I used a square 1/2 in. piece of oak that I ground down into the shape of the groove and put a slight bend in it since the seal groove is rounded .Then I packed it as tightly as I could with a small hammer laying on my back under the car. When it would take no more( probably 1/4 in. on each side) I cleaned the mating surfaces well leaving the slightest bit over , maybe 1/32 in.? and with the cap and new lower seal rolled in properly I put a TINY dab( I mean tiny) of black silicone sealer and torqued it down ....don`t want any space in the mating surface , will cause leaks. Just nice and tight fit. That`s how I did it with help from the forum ....thanks guys!........after a year or so now ....I still have a leak or more of a normal drip(normal to many of us and not so to the lucky few it seems that have a drip free engine) , but nothing to get excited about. Good luck!

Well I went to pack the upper seal with the old lower seal to fill the void. As soon as I pushed on it the old upper seal easily slid right out. Given this I decided to try the Sneaky Pete tool and I have to say it worked like a champ. I soaked the new top seal in oil then pinched it in the Chinese finger grip tool on the end of the wire after threading it over the crank. Lined everything up and had my son turn the engine by hand while I kept light pulling pressure on the new seal. The seal slid right into place in less than 30 seconds. This was the slickest tool I have used in a very long time. Given that it went so easy and quickly it will either be great or a great disappointment lol! I hope it works and seals up my leak so I can drive it without leaving a puddle everywhere I go.

Looks as if some one already pulled a seal through, stretched it out, and never packed it in.

Lol
You might be right Gene. I don't know if that is the case or if sitting for 15 years without starting caused it to dry out and shrink. Either way it was not fitting well at all. The new one is in and I have driven it for about 20 miles and looks like maybe I finally have it sealed up again. I greatly appreciate everyone's help and input! This is a great site with great people possessing some incredible knowledge. I am certainly happy to have this wonderful group to help out with my adventures in my old Chevrolets. Thanks again everyone and I will up date in few days or weeks to let you know if this has solved my rear main problem.

Yes, please keep us posted.

Just an after comment owing to the fact that this thread started out about the torque of the crankshaft main bolts.

Isn't it a fact that most any mechanic, tightening many bolts of different threads over many years, has developed a working feel for what is "tight." You merely pull down on it until your elbow sense says that is about it. It won't go any tighter.

That being so, then I suspect the reason for the specs as to torque is to protect the bolt. That is, so you won't exceed its strength and get into its elasticity. Streatching any bolt will have an adverse effect on its strength. Exceeding its elasticity will break the bolt or at least deform it.

So if you don't have a torque wrench just get the bolt tight. It will be tight enough. Of course you have to take in the type of bolt, the information on its head. its application, size and threads.

A calibrated torque wrench is nice to have but is not always essential to a good shade-tree overhaul.

What do the rest of you think?

Charlie

That may be true for things that don't require an exact calibrated setting. I have a friend named Nick that worked in a restoration shop and he can do pretty much as you explained. Whenever working with him if the bolt doesn't require a torque setting we just put things "Nick-tight". However when it comes to bearings and head bolts etc. the torque wrench comes out and proper sequences are followed.

I agree for most things that is adequate. It may even work for things like main bearing caps, rod caps etc. but given their location, amount of work it takes to get to them again and what happens if what I though was tight enough wasn't, I would rather go by a torque spec and know I did my best. For everyone's info I torqued them to 105 lbs. double checked the bearing clearance without the one shim that I found under one side of the rear main cap and both times came out with .001" clearance. With any luck I will be done opening up the bottom end of the engine for quite some time.

I packed the upper rope tight in the block and ended up trimming very little off of it. When I reassembled the main cap I used aviation form a gasket instead of silicon on both ends. I always have better luck with that then silicon anywhere I use it. Besides silicon is a mess.

Ps: Genes trick of taping the oil pan end gaskets around a coke can for a day worked like a champ. When I undid them from the can they were perfectly shaped to fit the curve around the front and rear mains! Thanks Gene!!

I say, use a torque wrench....don't guess as to how tight you think a bolt is tightened. When we rebuilt an engine, it costs a significant amount of time and money. If you don't own a torque wrench borrow one from a fellow car guy.

dtm

Originally the size of a spanner related to the size of the nut or bolt. Obviously the spanner got longer as the nut or bolt increased in size. If you extended the length of the spanner you risked snapping or at least stretching. This system worked for many centuries and basically still does. The latter day use of the tension wrench is just refining matters, particularly when it comes to things like cylinder heads where it gives that added accuracy and security.

Note: This is longer than it should be. Is nonsense. You may want to skip it. You've been warned.

Okay. I've been shot down.

Just answer me this? When was the last time you tore down a 216 (for instance) and found a main bolt loose? You know when you went to loosen it you found you could turn it with your fingers? Or found some of them in the bottom of the pan.

I still say that "muscle memory" is good enough and "tight"means tight without approaching the elasticity of the bolt. If you haven't had the experience of tightening bolts over a long period of time, then, a torque wrench is essential.

No matter how much you screw down on the bolt in the main cap the clearance is not going to change.

The crank is balanced and is just sitting there. When the engine is running the weight is evenly distributed through 360 degrees. I think that is about right.

So next time you put the mains back in your car just tighten down on the bolts. If you break one just grab a spare and don't exceed what broke the first one. You
muscles will remember and start to shout, "ease up, idiot, That is tight enough!"

Amaturs use torque wrenches. They have nice clean garages, tool chests so high they need a step stool to reach the top drawers and trash cans located here and there.

Professionals use recently calibrated torque wrenches. They have all the above but don't use the torque wrench unless the boss is looking. It stays in its little tray until the next calibration. They have drink machines and pictures of some "heavenly
Helens" on the walls.

Old timers use "muscle memory." (Just as good on mains and much faster.) Their tools are scattered and it takes time to look for the proper wrench. If they have one they don't know where it is and its out of calibration anyway. They have dogs lying around and have to watch where you step. There are tobacco stains on the unfinished concrete floor and the missus smokes a pipe.

Charlie

Well I have put a couple hundred miles on the car since changing the rear main seal top and bottom halves using the Sneaky Pete tool. I am happy to report that it appears as though we have stopped the leak. When I first installed it and put everything back together and test ran the engine with the car up on stands, it did seep out a little. I was really disappointed thinking all this work was a waste. I figured I would drive it for a while and see just how bad a failure it was. It turns out that it has sealed up and after 200 miles the rear main cap is dry! I am happy to report back that as of now it seems to have been a success. Hopefully it lasts. Now to fix the leaky transmission and torque tube.

Thank You Everyone for all your help!!

RM,

If it hasn't begun to leak after 200 miles, it means you did something wrong. You may need to tear it down to find out just what it was before the pistons begin to swap holes.

The transmission and drive line are supposed to leak as well. They cannot be sealed. Not supposed to be. Without those leaks and seeps the DOT won't know where the bumps are in the road and the signs that say "bump ahead" will just sit in the warehouse and gather dust. Yes, all those dark spots on the road are caused by Chevrolets marking their spots like a new puppy on your neighbors flower beds. You get the picture.

Just thought you ought to know,
Charlie