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1966-67 HCS rear main engine seal

66hcs-conv

Well-known member
Joined
Apr 1, 2007
Messages
360
Hi gang,

The rear main seal on our '66, 289 is leaking. I was thinking of having the whole engine rebuilt, but now I'm thinking of just doing the rear seal.

So my question is: is that seal the one piece type that requires the transmission to be removed, OR is it the rope type that is in two pieces?

Thanks, I appreciate your help.

Dave
 

robert campbell

Well-known member
Joined
Apr 10, 2007
Messages
4,321
Dave,
If it is the 66 engine then it is a two piece seal. You can do it in the car by dropping the pan and removing the rear main cap. They used to have a toll called a "sneaky pete" that helped pull the half of the seal under the crankshaft, but I have found using a small punch you can carefully tap on one side to drive it "around" the crank. Many times if you loosen the rest of the main caps it allows the crank to drop just a bit to assist. Some engines had a little "dimple" sticking up in the bottom of the seal groove above the crank to hold the seal from spinning. I do not think you have that.

Are you positive that the rear of the pan gasket is not leaking? I can look just like a rear main leak. Felpro sells a one piece pan gasket that is very trick and easy to install in the car. And it is reusable and you do not need to use sealer on it. You may want to try that first. I always use a block of wood and a hammer to remove the dimpling effect of over tightened pan bolts. Put an about 1 inch wide block under each hole and tap them flat from the engine side of the pan. This helps make a better seal when you reinstall.

Rob
 
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66hcs-conv

66hcs-conv

Well-known member
Joined
Apr 1, 2007
Messages
360
Rob,

Couple of month's ago I removed the oil pan cleaned it real good and put it upside down on a big piece of 1/2 inch steel - kinda like a surface plate.

I leveled all the holes and the pan itself. I did use the felpro gasket. I'm reasonably sure it is the rear main itself.

Still kicking around the idea of removing the engine, since it leaks and does burn a little oil. The engine has 140 K miles on it and I don't think it has ever been work on. I've had the valve covers off and it is not pretty in there!

to do, to do

Thanks for your advice, Dave
 

robert campbell

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Joined
Apr 10, 2007
Messages
4,321
Dave,
The main cause of death of a 289 is sucking a chunk of "stuff" up into the oil pump and seizing the pump and twisting the oil pump shaft off. One of the sources of small chunks is petrified exhaust valve seals. And the source of exhaust smoke. I have helped people extend their engines life by putting a set of new seals on the valves in the car. If you had the pan off you may have found a few pieces.

You can remove a valve cover and inspect the exhaust valve seals. Even if they have not fell apart yet they are petrified and no longer seal. Pull the plugs and use a plastic straw to move the piston up to the top. A brass hammer can help shock the stem seals if they are stuck. I replace the intake valve seals also. May as well while you are there.

If the engine still runs good when you start this will eliminate the smoke for quite a few "sunny driver" car years.

I assume that the timing chain has been replaced at some time? The old aluminum top gear with the hard plastic coating have usually died before 140k miles. They are another source of chunks in the pan. They are usually much larger and a light brown in color. The exhaust valve seal chunks need to small enough to go down the oil drain back holes on each end of the head.

Rob
 

Mosesatm

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Joined
Jan 18, 2005
Messages
9,009
The chunks of petrified seal can also plug the oil return holes causing the oil to stay in the top part of the engine. That creates a huge problem.
 
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66hcs-conv

66hcs-conv

Well-known member
Joined
Apr 1, 2007
Messages
360
WOW, thanks for the information.

I didn't see any chunks of anything when I had the pan off, and I would be willing to bet the timing chain is the original. I have all the receipts from day one of work that has been done, & no engine work that I can see has ever been done. yikes !

Looking more & more that I should pull the engine & have it gone thru.

Thanks again for your help.

Dave
 

robert campbell

Well-known member
Joined
Apr 10, 2007
Messages
4,321
a quick timing chain test it to put a 15/16 socket and ratchet on the vibration damper nut with the distributor cap off. Roll the engine by hand in one direction and watch the rotor move. Then roll it back the other direction. Some slop is expected, but if roll about 10 minutes on the clock so to speak and the rotor does not move, you better address the timing chain and sprockets.

I would be very surprised if it has not been replaced. The upper sprockets were known for early failure and replace years ago. Not a bad job to pull the water pump and timing cover off..... Yup, you get to loosen the pan bolts once again to get a bit of clearance to pull to timing cover off the pan gasket....

Good time to clean up the front of the engine!!!

Rob
 
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