68 rear main seal?
 

I have a leak, not huge but it’s there coming from backside of the motor. The engine is 400 ho (if that matters) and never been opened that I can tell.
I’m replacing valve cover gaskets and hoping that is the leak. IF not, then I assume rear main or pan. Can this be done without the engine being lifted? What is the going rate to do rear main seal and pan gasket?

I would hate to try to do it while the engine was in the car. If you do a rope seal, it needs to be packed in. There is a tool that grabs a rope seal with the crank still in the engine that can be used. I was able to successfully change a rope seal with the crank still in the engine but the engine was also on an engine stand. It really wasn't all that hard but I would imagine it would have been a nightmare with the engine still in the car. A lot of care also needs to be taken to seal the oil pan up. The seal that goes over the rear main is sometimes difficult to get to seal off. The seal likes to push its way out of the cap grove, especially if you try to use the rubber seals that fel pro offers. A cork gasket that goes over the rear main cap is less likely to push out of the grove if the 4 piece pan gasket is used. A one piece pan gasket is money well spent in my opinion. I would definitely recommend pulling the engine to make sure it is done once and done right. As far as time, it would take a lot less time to pull the engine to replace the rear main seal and oil pan gasket as opposed to changing both while the engine was still in the car.

Well I’m hoping it’s just valv e covers but I’m not that lucky. If it’s not too bad I may leave it alone for a bit but I really hate leaks. What material do you recommend for the rear seal?

I prefer a Best brand rope seal. The fel pro rope seals aren’t worth installing. I don’t know about the new viton seals. I have never used one so I can’t comment on them.

I put a one piece Viton seal in mine and it has been perfect so far, no leaks.

If you try to do a rope rear main in the car, chances are nearly 100% that it will leak.

Packing the rear main has never worked for me because if it's old and leaking, the rope has deteriorated and packing new ends in it won't hold the oil back.

Pulling a new rope in with Chinese fingers damages the rope even when funnels are used, been there and done it.

I've never put a one piece Viton or Neoprene in a Pontiac, I've done others, but the crank does need to come out of the block, requiring pulling the engine. Two piece Viton/Neoprene needs to be silicone/glued in the block and left to set up for 24 hours with the main cap installed, before installing the crank.

Using the Best graphite rope seal would be best to pull the crank and fit the upper half into the block for a leak free install.

Just to sum it up, the engine should come out for best results no matter what seal you choose. Whoever you select to do the work should be intimately familiar with Pontiac rear main seals (most general service garages probably never even attempted to install a new main seal in a Pontiac).

Even someone familiar with them can have a leaker, a 24 hour test with the engine filled with oil and tipping the engine so the engine oil is against the seal minimizes the possibility of installing the engine and having it leak. Think of it a pre test before installing the engine back into the chassis.

Labor is going to be expensive, I would guess 12-15 hours depending upon labor rate $1000 and up.

My qualifications to post on the subject, 40+ years as a mechanic and have worked at Pontiac, Buick, and Olds dealerships, all of which used rope rear main seals. Owned my own garage which specialized in Pontiacs, but have worked on damn near anything automotive.

FWIW, if you came into my garage, I would insist upon pulling the engine, because I have tried and won some, and lost some trying to do them in the car. Buicks, Olds, and even chevy are much narrower blocks and the pan comes off and is able to be removed in the chassis. Pontiac is really tough to get off in chassis, I have done it twice, and for all the aggravation pulling the engine is easiest and you'll have a much better job resealing a Pontiac.

Good luck...……..:)

Tony, I've used the BOP 2 piece Viton rear mains on several engines. No leaks from any of them...not a drop, and many years and thousands of miles have passed. We put a Viton BOP one-piece in Will's '69 (they weren't yet available when I did my engines) and it is working fine as well. To do it right, you need to pull the engine. It is not a time saver to try to do the job 'in car' with a Pontiac. BTDT, and it doesn't pay. It takes longer, and you end up with a marginal job and crap in your eyes and all over. My advice, knowing your car, would be to pull the engine, replace the rear main seal, replace all the gaskets (except the head gaskets), replace the core plugs, replace the timing gear set, and while the engine is out, you can spruce up the engine bay. When it all goes back together, you will have a low mile, spotless, reliable HO powered GTO. Your car definitely rates this!

Yeah this sounds like it’s the way to go now. I guess a chance to paint the engine too.

Out of curiosity what makes the Pontiac harder? I had this done in the 69 Camaro small block I had, inside the car.

Even getting the oil pan off and out is a PITA on a Pontiac when engine is on the mounts. Easier to pull the engine even if that's all you wanted to do.

I touched on that reason in my post, the pan is wider, the main caps hang down further on a Pontiac, the crankshaft is also much more mass and hangs down further into the pan. The crank also has large counterweights.

All the mass that makes the Pontiac bottom end stronger than other brands make obstacles that complicate pulling the pan in chassis.

Oil Pan does not get out on a 68 GTO. I tried within this decade and no way.
Thought i did it in my 20s...

Pan drops for a 69 Bird when you get into it,

Mark, you have to take the front main cap off, and have the crank so the rods are at 6:00 to get it off, and you still have to wrestle with it. No way at 66 YO, I'd even attempt it.

What was done on my camaro was remove trans, unbolt motor mounts, lift motor up about 6 inches to clear the pan over frame/cross member. Push out the rear seal and push in another with cap off.
At this point I’m thinking I’ll just change valve cover gaskets for now and see how bad it is after.
If it’s coming all the way out I’d rather wait and paint it too. There’s not much paint left on it after 50 years. Runs great though!

It might sound ridiculous ... but when I was 19 I'd actually pull the engine out of my GTO to clean and touch up the paint about every year :)

I used to do the same! Not so much anymore ;)

Agree with the others, you've gotta pull it to do the rear main.

Yep, you gotta be careful with that ... the last time I pulled it out about 35 years ago .... it stayed out, and it's still out ... but soon to go back in !

I believe that. Did have the bravery at the time for a let down.

Rear seal
 

I have a 70 judge (ra3) also with rear seal leak. I had concluded (and this thread confirms) that given access and complicated rope seal would need to pull motor. Car is restored and engine is numbers matching so obviously want someone to do this properly and with appropriate level of care. Can anyone recommend an appropriate Pontiac engine guy in central/northern NJ?

Check with Pickett automotive.Pontiac racer.Tom