Rubber Rear Main Seal

[OlsonsGaskets]

Originally Posted by 63gmc4x4

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

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

Had a little time today to look into this Ebay posting. Looks like I was a little too hasty in my previous post. I sincerely doubt this will work (see picture for comparison).

Under "Item Specifics" of the Ebay listing it gives a manufacturer part number of RS29025 which is ROL brand. The interchange that they list is BS30136 (Felpro) and JV723P (Victor). I recognized these as the Ford V8 260, 289, 302 ci rear main seal. I have a BS30136 on the shelf so I thought I would compare.

Here's what I found. The Ford is much larger over all, however it has a thinner width .230" compared to the GMC seal which has a .290" width.

FYI. The old Victor part number for the rubber seal is JV616. I looked back in my Victor catalogs and this Part number doesn't appear until 1973. It appears prior to 1973 only the rope (Victor p/n JV716) was available, but the rubber should work retroactively for earlier engines.

[BobBray]

What you say makes sense, when I rebuilt my 351 20 years ago I bought a FelPro full gasket set, and it included a 2 piece rubber lip seal and the wedge type soak in oil side seals. I do have a later issue FelPro BS40048 and it's a rope seal with pipe cleaners and a small tube of silicone.

As far as the round rubber plugs are concerned, all they really do is provide a smooth surface for the oil pan gasket where it goes over the holes for the rear main bearing cap bolts. The concave side goes towards the bolt heads, my guess is they made them like that because the bolt heads are not exact so the plugs would conform a bit to be the right height. I think you would be fine making the plugs flat, it they are a bit too low add a bit of silicone, if too high just shave them off with a razor blade.

Thanks for making the effort to furnish gaskets and seals for these old engines!

[63gmc4x4]

[QUOTE=OlsonsGaskets;78214]Had a little time today to look into this Ebay posting. Looks like I was a little too hasty in my previous post. I sincerely doubt this will work (see picture for comparison).

I actually bought that from eBay that posted to try it out , i pulled out my original one in my 401 this morning it was a rubber one and it's stamped GMC on it. I should have taken a picture to compare the two before I installed it and match it up to this one from eBay and it's exactly the same. I installed it this morning. Fit perfectly!

[63gmc4x4]

Originally Posted by OlsonsGaskets

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

It is the correct seal, looks new old stock, I remove my GMC sale and held it up next to it. Exactly the same size so I installed it installed it this morning fit perfectly! It came in a bag and it said 17091 on the bag and I also confirmed with the seller before I purchased it. He confirmed it is the correct Seal and had about 10 of them left

[Prowbar]

[QUOTE=63gmc4x4;78220]

Originally Posted by OlsonsGaskets

Had a little time today to look into this Ebay posting. Looks like I was a little too hasty in my previous post. I sincerely doubt this will work (see picture for comparison).

I actually bought that from eBay that posted to try it out , i pulled out my original one in my 401 this morning it was a rubber one and it's stamped GMC on it. I should have taken a picture to compare the two before I installed it and match it up to this one from eBay and it's exactly the same. I installed it this morning. Fit perfectly!

Good to hear that it fits! Was the sealing surface left stock on your 401? (i.e. with the serrations?)

@Olsonsgaskets I believe the plugs is concave to clear the 12 point bolt head. Suppose you could make them a little shorter to cut down production costs.

If you need any measurements of the NOS rubber seal (17091) that I posted pictures of, contact me.

[63gmc4x4]

[QUOTE=Prowbar;78222]

Originally Posted by 63gmc4x4

Good to hear that it fits! Was the sealing surface left stock on your 401? (i.e. with the serrations?)

@Olsonsgaskets I believe the plugs is concave to clear the 12 point bolt head. Suppose you could make them a little shorter to cut down production costs.

If you need any measurements of the NOS rubber seal (17091) that I posted pictures of, contact me.

Yes very light, but looks like the old seal was sealing just fine!