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Discussion Starter #1
What is involved in replacing the rear main seal on a 68 302? I'm not doubting I can do it and I have a manual and such, but I wanted to get some idea of it from people that have maybe done it. It's a two-piece seal isn't it?

Korey
 

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Yes, it's a 2 piece rope seal and a royal PIA to get in correctly with the engine in the car. Personally I'd rather pay someone to do that kind of work who has the right tools and a lift, but 20 years ago I was a bit more energetic and would've done it myself. It's not rocket science, it just takes patience.
 

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Discussion Starter #3
Can I use a 2-piece neoprene seal? I think I'm doing it myself as I have all the time in the world to work on it.
 

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Discussion Starter #4
anybody else?
 

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yes you can use the two piece seal but you have to make sure you remove the pin that holds the rope seal in place before you install the newer two piece seal.

You will have to pull the trans and flywheel. Drop the oil pan. Remove rear main cap and lossen the other main caps. may as well check the bearing while your in there, rod bearings to and a new oil pump wouldn't hurt.
 

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The original is a two piece, rope seal as mentioned. It is not a very difficult task with the motor out of the car; I just replaced mine this past winter when I had the motor out. I have heard of many people replacing the rear main with the motor in the car but it does not sound like a fun process to me.

How bad is it leaking? If it is only a minor leak I would suggest trying an additive like "Bars" Rear Main Seal leak stop. The stuff works on minor leaks and is far cheaper than paying someone else to change it for you.

I'm not overly mechanically inclined but I'm not affraid to try something and I did not have a problem replacing the rear main myself. Try the additive first if it is a minor leak. If you plan on pulling the motor anytime in the future to do some work on it that would be a great time to change the seal. I'd say that you are looking at over $1000 to pay someone at a garage to change the seal for you.
 

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Discussion Starter #7
That's what I figured. The engine was supposedly rebuilt around 35k miles ago, so I didn't see any need to pull it out. I have a sneaky pete main seal system sitting in the garage... I wonder if that would help. It's not a bad leak, but I like to have stuff buttoned up. I may just put it up on ramps, drop the tranny and such and check it out.
 

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It's also not too hard with the engine in the chassis. And you don't have to remove the engine or transmission. Just the oil pan.
 

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Discussion Starter #9
Yep, I just read that actually. :)
 

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wally05 said:
That's what I figured. The engine was supposedly rebuilt around 35k miles ago, so I didn't see any need to pull it out. I have a sneaky pete main seal system sitting in the garage... I wonder if that would help. It's not a bad leak, but I like to have stuff buttoned up. I may just put it up on ramps, drop the tranny and such and check it out.
I've never seen anybody use a 'sneaky pete' and not give up on it. The neoprene seal is the way to go. When we've done SBCs, we just drained the oil, pulled the pan, loosened the rear main, and swapped it out and re-assembled.
 

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Don't forget to drive the neoprene upper a little futher into the block so one side is sticking out a little. I've had good luck doing it that way. Plus use some Gold hi temp silicone on each end of the seal as well as on the front corners. I've never loosened the rear main..I just lube the seal and machined opening with WD-40 and drive the seal slowly and carefully with a small drift punch against the wire support in the seal itself. Next time, I'll try it Kyle's way, though, sounds like it would take less time.
 

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Discussion Starter #12
Thanks for the tips, guys. I appreciate it. :) Any other tips?

Korey
 

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wally05 said:
Thanks for the tips, guys. I appreciate it. :) Any other tips?

Korey
Yes, the neoprene seal has a front and rear to it. The front is the side of the seal that has a thin lip to it. The lip faces the front of the engine. I've seen some installations where the installer flushed the seal with the height of the main cap, just the way a bearing is installed. The correct installation has the seal "offset" relative to the face of the cap. One side should have about 3/8ths of an inch of seal extending above it. install the seal in the block with 3/8ths extending out, on the other side. When the cap is mounted to the saddle in the block, th petruding ends fit into the recesses. What this does is to bury within the block and cap, the joint between the upper and lower halves,thus minimizing the chance of a leak. Like another post states, use some type of sealer (black RTV?) on the face of the cap, at the corners where the seal sits and extending forward a bit. A Haynes Manual will have a diagram and photo to show where to apply the stuff.
 
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