# 1966 GTO Rear Main Seal question



## Huckleberry66 (Apr 5, 2012)

Hi,
I'm Nate - new to the forum, but have been browsing for a while and getting a lot of good knowledge. I just bought a 66 GTO with a recent (3 years) rotisserie restoration. When i bought it i paid a mechanic to put it through the paces, and it has a very minor oil leak. He thinks its the rear main seal, and judging from the research I've done, that calls for an engine pull, rather than trying to access it from the tranny. I am just looking for a ballpark opinion on what a mechanic would charge to pull the engine and replace the seal/inspect for leaks (how many man hours - realizing that the replacement seal is inexpensive) before i start shopping around some of the classic car restoration places in town. I'm willing to drop around 1,000/1250$ - am i even close? Not really considering using band-aids/snake oil methods, since i paid so much for the car i want it done right. Thanks for any input/clarifications you might add! Oh yeah, definitely would go with a newer technology seal over the rope seal.


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## BearGFR (Aug 25, 2008)

For some reason, getting a good seal on the rear main in these engines requires a combination of skill, experience, black voodoo, and dumb luck. First I'd ask, how badly/how much is it leaking, and are you SURE it's coming from the main (and not just trickling down to that point from some other source - like a valve cover or the oil filter housing).

Of course it's up to you to decide if you can live with it or not, but considering you could spend significant cash paying someone to do it (yes, to do it right the engine has to come out and the crank has to come out), and STILL have the problem (or worse) unless they've got specific skills doing this job successfully on Pontiacs (chevy experience doesn't apply), I'd think pretty hard before I went that route.

Bear


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## lars (Sep 28, 2004)

:agree
I've been building Pontiac engines for over 30 years, and I have pretty good luck with the seals, but it's a real cliffhanger every time I fire up a new engine on the stand. If you get it to seal tight, there's no assurance that it will stay drip-free past the first year. I've had a couple seals over this time period wad up and fail completely within the first 1000 miles, and I've had to re-do those completely - it's a roll of the dice combined with skill, experience, and blind luck, as Bear stated above. If you just have a little drip, I'd leave it - that's what drip pans are for... If it's leaking bad enough that you're loosing significant oil and getting the bottom of your car coated, you might think about doing the seal. Make sure the guy doing it has built Pontiacs before...

By the way, unlike others here, I've had terrible luck (100% failure rate) with the "new technology" seals, and I've had at least a 95% success rate with the old rope seals.

Lars


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## geeteeohguy (Feb 2, 2008)

I've done three of them in the past 3 years, with a 100% success rate....(so far!). I used the new technology Viton seal from BOP on each, and followed the instructions to a "T". From what I've read, the new BestGasket Graphtite square-sectioned rope seals are just about fool proof, though. They are more forgiving to slight imperfections on the rear crank journal and bearing cap area, and are the choice of many Pontiac engine builders. I have an original style asbestos rope seal in my '65 GTO, and that engine was overhauled by myself in 1981. It's still leak free. The asbrestos-FREE rope seal I installed in my '67 GTO in 1988 started to leak within the first year or less. I finally replaced it last year. It's an inexpensive part, but not a place to take chances due to the labor intensity of the job. Agreed, have a PONTIAC guy do the job.


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## Huckleberry66 (Apr 5, 2012)

Guys - Thanks for taking the time to respond to my initial post...I will definitely take your input to heart, and make sure i have a Pontiac guy look it over. Appreciate it!


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## GTO JUDGE (May 14, 2005)

I had thought I had a rear main leak when I purchased the car. I took the car to a guy locally for engine work and one of the items was to replace this seal. I had gotten the Vitron seal. The engine was not removed. The trans was removed for rebuild while it was out all the guy did was loosen the motor mounts and jack the engine up enough to give him room. 

Turned out the seal was not leaking it was a bad oil pan that was leaking and throwing oil out the front giving the appearance of a seal leak. The oil pan seal was shot and some bonehead I learned used JB Weld on multiple spots to seal holes. Needless to say I got the correct OEM pan from a guy on the PY site in NY. 

At any rate, someone had a graphite rope seal in that was holding fine I had it replaced anyway with the Vitron. After the seal was installed he allowed the car to sit a day or so for everything to set properly. No issues no leaks 3 years later.


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