1969 Skylark 350 rear main oil leak, replacement methods?

I drove my 1969 Skylark for the first time since the day I bought it back in 1980. The last 2 years of my spare time has really paid off in finishing my lifelong ground up project. Unfortunately, her maiden voyage has shown the rear main seal oil to leak. After researching the repair process to correct this condition, the owners manual states that in order to change out the upper half of the faulty seal, that THE CRANK SHAFT HAS TO BE REMOVED.
Does anybody have a cheat around this???
I have been studying the rods and mains with the oil pan removed;
1) Has anyone ever loosened all the cap bolts and let the rear of the crank hang on the front timing chain? I never have and before I do, I was wondering if there is a noticeable rear droop? Or maybe the crank doesn't hang or move at all? Will this process hurt the bearings or damage anything ?I am only looking to increase the existing rear gap at the top half of the crank seal groove, so a new rope seal can be threaded into this top groove. Right now there is no viable process if the groove is not made larger, which would happen if the crank could be slight dropped down, but only in the rear. Hopefully this slight crankshaft rear droop will not adversely affect the timing chain, or the adjustment of it once crank main caps are torqued back into place, after the new rope seal is replaced into the top groove??? Am I missing or overlooking something?
Just spit balling here, but I would really prefer to not have to pull my engine and all the work that goes along with that (hood, headers, belts, radiator, .................)
Since I have heard from many that this is a Buick engine design characteristic, there has got to be some ole time Buick Techs that have a way around this. Has anyone heard of fixing this with Fiberglass resin? If so, I am assuming that the rope seal is soaked in a resin mix first, ok, but the problem of a new uncompressed sized seal getting installed into a compressed semi circle groove still exists. Thus the desire to increase the diameter of this groove, by dropping the crank.
Anybody?

 

Maybe it would be a lot easier to install a Rubber seal instead of a Rope seal.
Maybe you can oil-up the rubber seal and slid it into the upper half of the main.

The Rope seal is difficult to install and has to be cut to size which can be a pain too.
I've been told Buick has a tool to install a Rope seals. If an installation tool is required, you might have to pull the engine.
Hope this helps you.

350 Buick Rear Main Seal Kit Rubber Crank 1968 1969 1970 1971 1972 1973 1974 75

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In the "olde days" there was a method of "pulling" the upper half of the rope seal wit a "T" handle with the bottom cap removed. It was a "hit or miss", if you were lucky, you could get some time before it started leaking again, or it simply failed to fix the problem. If you want to go that route, do some digging and see if it is still an option.

If you decide to use the "rubber" seal (and pull the crank), you will need to polish the crank in the area marked, (image below) or have it done, otherwise the "rubber" seal will be "destroyed" from the oil transfer grooves for the rope seal chewing up the rubber and you will be back to this place again. You cannot simply stuff a rubber seal in what you have and expect it will work. It will not.

If the car has high mileage, you might as well figure on doing a proper rebuild.

You can roll the dice and hole for a low cost fix, but almost always, you will realize down the road, that you threw away a lot of money, incrementally and never received more than frustration for it, than had you simply done it properly the first time.


That said from the point of view of "it's easy for someone else to spend your time and your money" and the other side of that coin being, "there are innumerable people that will tell you how to do it cheap and promise you the world, yet they cannot be found when it fails'.

The middle of the coin is, deciding what you want and how much you are willing to pay, to achieve it.

 

Question - The marks I see on the crank (you marked), I assumed that are from the rope seal?

This is the reason that area of the crank has to be polished.

I assume these marks from the rope seal will chew-up the rubber seal.

Nice to know, thanks for the education, much appreciated.

FYI: I only assumed one could slid a oil coated rubber seal into the upper-half of the main, looked to me as feasible, guess not. Again thanks for your advise.
One can always hope for a simple solution when faced with lots of labor involved. Vet (Navy)

 

Those "marks" were the knurling done at the factory on the crankshaft to "bring in" oil to provide a constant lubrication of the rope seal and create a bearing surface. The goal and purpose was to permit a slight and replenished oil film to allow the rope seal to be a "seal", and the oil film protected the rope seal from wearing from friction. (the marks are not a result of the rope seal)

It was, and is, a very successful method used in a great number of rotating oil seal machines.

But, if using a newer "rubber seal" (neoprene, silicone, rubber, etc.) those "knurled grooves" become detrimental to the seal, and will often "erode" the seals and result in greater leaks.

One cannot simply lay a crank in an engine and use the new "rubber" seals, without polishing the crank to remove these "cuts" (knurling).

There were many times folk tried to "pull" a rubber seal over the top of the crank, and put the bottom half in the cap and it almost always failed.

Doing the same thing with a rope seal, might work, but it was a crap shoot.

In the old days, it may be a thing one would do to keep the family grocery getter moving for another year, but for people nowadays, with the money and effort it takes to keep these cars running for our purposes (luxury, not necessity), it is not the best application.

You either spend the coin to do it right, or you find a hobby that matches your wallet.

Might seem like harsh words, but it is reality.

 

Factory created a knurl to retain oil for the rope seal, what a clever idea.
Nice to know!
Glad they didn't do that on the front crank seal because when my front seal leaked, I replaced the the timing change cover with a TA model that has a front installed neoprene seal.
No more leaks.

As for the rear main knurl, I bet the surface was smoothed.

I say this because knurling has the effect of pushing the metal upwards and would chew the hell out of the rope seal as the crank is rotating. There are better machining techniques
to accomplish grooves to hold oil to lubricate the rope seal.

I've been a machinist & Tool and Die maker for over 40+ years. Vet​

 

Yes. The knurling served two purposes.

1. To allow fresh oil in to cool and flush the seal/crank.
2. To "push" the oil flow back into the crankcase, and prevent migration out (leak).

Rope seals are over 100 years old in use and still used today.

And, many seals, like front seals in timing covers and transmission output shaft seals actually use the same method, but the seal itself has the "knurling" (angle grooves) in the seal itself to accomplish the same result as a crank with grooves (knurling) cut into its surface.

 

I've been a machinist & Tool and Die maker

Check out this product.
This might work for you, but, see if you can find anybody that has used it, because I haven't. Vet

 

That was the method in the GM service manuals. We did that all the time and as far as I know, I never had one leak. I did this on my Cutlass over 15 years ago and it's still dry.

 

100 year old rope seals were made with asbestos (as were our 50 year old Buicks’ seals). New ones are not, so even the best, most careful install is compromised from the get go.
Patrick

 

Why is the crank painted red?

 

Hi Mark, I have a friend of mine that paints the entire inside of this block. Uses a high gloss high heat paint, says it helps the oil to drain faster to the oil pan/oil pickup.
His reason is, the paint covers up the casting surface, so oil flows faster.

Not sure I by that theory. Vet

 

Glyptol I believe it’s called, never seen it on a crank

 

You're right on, Eastwood sales it. I thought he was pulling my leg. Learn something every day.

 

Thanks everybody for your input and ideas. The idea regarding using the rubber seal kit as a replacement was at first my thought, but the method of getting them installed did not sit right with me. If there is enough loose play to slip in, how much oil SEALING will they actually be doing?

 

What I’ve done “In chassis” as far as rear main NEOPRENE seal,
Loosen DO NOT REMOVE main cap bolts, obviously remove #5 bolts and cap.
The crank will lower/drop a few thousandths which typically will be enough to remove the rope seal and install the neoprene seal.
As far as the knurling on the crank, don’t worry about it, my crank still has it with the neoprene seal, I ALWAYS forget to have it polished smooth.
The purpose of it was to push the oil back into the crankcase if oil made it under the rope seal.

 

.....To pick up where I left off, (I was not finished with my post, fat fingers hit wrong key)...
the "repacking of the upper rope seal" sounds like its the best proven method so far. Thank you very much Smartin, for the notes and the great video, and 1973gs for your experience at doing/have done this procedure. Definitely no substitute for experience. All others, thank you for your input as well. As always, I appreciate an owners/builders point of view most of all. If anyone has any more tips on this procedure, I'm all ears. THANKS EVERYBODY

 

Forgot to mention the transmission will still be supporting the rear of the crank.