Rubber Rear Main Seal

[Prowbar]

One thing I'm wondering about:
For the rope seal to be lubricated, the V6 crankshaft has angled serrations cut in the crankshaft. I added a picture that I had, it might be difficult to see because of the assembly lube.

Do these serrations interfere with the sealing capability of the lip seal?

Should one have to regrind the seal surface on the crank for the seal to work properly?

[James]

Originally Posted by Prowbar

Do these serrations interfere with the sealing capability of the lip seal?

Should one have to regrind the seal surface on the crank for the seal to work properly?

The way the serrations is made on the shaft, as the crankshaft rotate the serrations try to pull the excess oil back into the crankcase. And the rope seal works very well with this because it has a wide surface for the seal to work with.

The rubber seal (as I understand it) needs a smooth surface, just like the front seal has on the crankshaft hub. It only has a thin lip that make contact with the shaft.

I don't know if placing a rubber seal on a shaft with serrations would be any better or not. In my opinions I think the rope seal is better and the rubber seal. The rubber seal on the serrations could be more prone to leakage due to the serrations.

[63gmc4x4]

I found this listing on eBay, do they look correct?

https://www.ebay.com/itm/38723916898...mis&media=COPY

[Prowbar]

Originally Posted by 63gmc4x4

I found this listing on eBay, do they look correct?

https://www.ebay.com/itm/38723916898...mis&media=COPY

Yes, these are the right rear main seals. Take a look: https://www.finditparts.com/products...el-pro-bs40048
I have the Detroit 17091.

@63GMC4x4 did you regrind the sealing surface before installing the lip seal? Do you have any leakage?

[Funky61]

Do these Rubber seals also come with the water absorbing pipe-cleaner looking side seals, used with the rope seal kit?


I have never done this before and was curious on the procedure.

https://www.youtube.com/watch?v=Ieck...bGR3zH&index=4

Whole procedure on the Rope seal type of installation starting around 16:54.

[Prowbar]

Mine did not come with anything other than the 2 seal halves. No instructions in or on the box either. Looking at the Fel Pro pictures of the same seal, it seems like it came with the gasket/rope type side seals and the 2 rubber plugs.

The seal installation like he did in the video is sloppy, you're supposed to trim the seal with a clean cut. The pipe cleaners are soaked in water and RTV is squeezed in to form the seal. The water helps it to cure.
Equally important to put a little bit of RTV/sealer between the main bearing cap halves to prevent any leakage.
The 2 plugs are installed to cap off 2 holes in the bearing cap or block, can't remember what the purpose of the holes is.

[BobBray]

Guys, look at this. I wonder if a rear main seal off a Pontiac 301 would work:

http://www.wallaceracing.com/rear-ma...erchanges.html

[Prowbar]

Interesting, I looked at this also. Going by the interchangeability, the seal groove in the block and cap should have the same dimension as the Pontiac I'm assuming.

If the assumption is correct, the only variable is the GMC V6 journal diameter vs the Pontiac journal.

To get a dimension for the sealing journal on a Pontiac I found this:

https://www.tinindianperformance.com...ontiac-engine/

3 inch main journal: 3.188" inch sealing journal
3.25 inch main journal: 3.436" inch sealing journal

Can anyone measure the crank seal journal diameter of the GMC V6? Don't have one apart to check right now.

[BobBray]

I tried to look it up, but the service manual only gives the O.D. of the rear main bearing journal, which is 3.1239". It may be the same diameter where the seal rides.

Most Pontiac V-8's also used a rope rear main seal. I am rebuilding a Pontiac 326 for my cousin as we speak and can verify!. The 301 was a real oddball, most everything about it is different compared to older Pontiacs.

[OlsonsGaskets]

Originally Posted by Prowbar

Yes, these are the right rear main seals. Take a look: https://www.finditparts.com/products...el-pro-bs40048
I have the Detroit 17091.

@63GMC4x4 did you regrind the sealing surface before installing the lip seal? Do you have any leakage?

Looking at this Ebay listing I would say it is correct for the GMC V6. I can't be 100% sure without holding them in my hand. Also what is not clear to me is if these are new product or if they are old stock. I don't need to reinvent the wheel if this dealer has already got the solution. Will have to do some checking here.

Regarding Felpro BS40048: At some point 5 to 10 years ago they switched from rubber to rope and kept the part number the same. I got burned by that. Now BS40048 is discountinued altogether. So if you're trying to source an old Felpro set through Ebay it's a crap shoot as to whether you'll get a rope set or rubber set. A really old superceded Felpro part number for the original rope seal with cylinder block plugs and wedge shaped side caps was BS12946.

To my knowledge there is no one producing the round rubber cylinder block plugs that was originally provided in these rear main seal kits. I still provide these in my rope rear main seal kits because I've junked out a lot of old sets but my supply is running low. What I need to know is does the plug need to be designed exactly like the originals with the concave divot on one side or could I just produce a slightly thinner plug without the divot? Anyone out there with insight into this?
Thanks