Lotus Elan

Rope seal leaks - PSA (with pictures)

PostPost by: benymazz » Fri May 13, 2022 7:26 pm

TL;DR: If you have had your block line bored and fitted steel mains, check your rear seal carrier to make sure it doesn't hit a bearing cap before it hits the block. And make sure that your seal carrier doesn't have a massive banana in the middle of it.

While I had the transmission out of my Elan last week to rebuild it, since I had the engine out as well I decided to try to fix some of the oil leaks. My engine is a 4-bolt rope seal engine, so I know to expect some leaks from the rear main, but I felt that what I had from that area was excessive, especially because the last time I replaced the rear main (just two years and ~8,000 miles ago) I used a braided graphite type which is supposed to be a superior material.

I do not know how well the seal was still functioning, but a major problem revealed itself once I removed the seal carrier. The sealant pattern (easily spotted when using a certain Aussie's favorite sealant :wink: ) on the carrier revealed that part was making very poor, if any, contact with the block and/or paper gasket.

IMG_9414.jpg and


Further examination verified this issue and showed a visible gap between the carrier and block (no gasket in place in photo)

IMG_9416.jpg and


With the facts laid out, now it's time for conjectures: While it's definitely possible that my carrier was dropped/beaten/pried/abused in the past, when I dug an extra out of the pile/hoard and fitted it up, I noticed that there was some light interference between the inner edge of the carrier and the rearmost main bearing cap. When I built the engine two years ago I had the block modified to take steel mains and it appears that the edge of #5 just barely hangs over the edge of the block.

IMG_9415.jpg and


It may be possible that this small lip and the force of tightening the mounting bolts up distorted my carrier. I have my doubts, because I would expect a witness mark on the carrier. Regardless, the bearing cap was still preventing an ideal fitup between my spare carrier and the block, so I filed a small relief in this area.

IMG_9417.jpg and

IMG_9419.jpg and


After adding this relief, the carrier sits flat against the block, as it should.

I was up into the wee hours of the morning yesterday reinstalling the engine and transmission, the car is back on the road now, so I'll know soon enough if this took care of the worst of the leaking.
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PostPost by: gjz30075 » Sat May 14, 2022 8:24 am

Nice writeup, thanks. Also, line boring the block and caps moves the centerline of the crankshaft
upward which could also affect the sealing.
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PostPost by: RichardHawkins » Sat May 14, 2022 7:39 pm

Bennymazz,

In California Keith Franck runs a web site called vintage technology garage. Keith has a 4 bolt crankshaft and has been working on the leak problem, his experience may be useful.

Hope this helps,

Richard Hawkins
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PostPost by: Quart Meg Miles » Sun May 15, 2022 11:01 pm

I'm interested to know how your rope seals really function, Ben, as I thought that I had mine tamed too. Just a few weeks ago someone (forgotten his name, sorry) posted an aside that what he thought was a rope seal leak was actually coming secretly from the rubber tube between head and block just above the fuel pump. I've got my head off at the moment and that tube is rubbish at both ends and I believe I forgot to fit it and forced it in afterwards a few years ago, so I'm hopeful that my oil torrent will stop like his did when I refit the head this time.

BTW, I'm interested to know the source of your rope seals as the present ones over here are too big to fit, or were five years ago, and mine were from Wilkin's floor sweepings, literally!.
Meg

26/4088 1965 S1½ Old and scruffy but in perfect working order; the car too.
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PostPost by: Mazzini » Mon May 16, 2022 8:05 am

RichardHawkins wrote:Bennymazz,

In California Keith Franck runs a web site called vintage technology garage. Keith has a 4 bolt crankshaft and has been working on the leak problem, his experience may be useful.

Hope this helps,

Richard Hawkins


Keith is a retired scientist (NASA or JPL I think) whom seems to have devoted his life to building a leak free Mk 1 TC and making the carbs work like fuel injection.

Keith recommends the use of Graphtite seals. I followed his recommendations and can confirm that these seals do work, but and it's a big but, they have to be staked into the housing to stop them rotating along with the crank. Keith sent me a photo of the method he used (three fine spikes). If I can find the photo I'll post it.

Meg, if you do decide to go down this route PM me your address and I'll send you new seal kit (for a small donation to the Ukraine fund)
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PostPost by: Mazzini » Mon May 16, 2022 8:12 am

Its a Best Gasket -1968-1976 Pontiac 455 428 | Rope Rear Main Bearing Seal Set. Available on eBay from the US.
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PostPost by: benymazz » Mon May 16, 2022 9:41 pm

RichardHawkins wrote:Bennymazz,

In California Keith Franck runs a web site called vintage technology garage. Keith has a 4 bolt crankshaft and has been working on the leak problem, his experience may be useful.

Hope this helps,

Richard Hawkins


I am on the vintage technology garage group. I actually applied his modifications to my engine this time around. They consist of, as some others have stated already:

1. Using a braided teflon/graphite rope seal as opposed to the ones commonly available from the usual suspects. This is a seal marketed for sale for use on Pontiac 421-455 engines, made by a company called Best Gasket, and has the part number 6382S.

2. Installation of a Kapton "bib" or "shield" behind the 5th main bearing cap. This is intended to stop the lubricating oil to the 5th main bearing from "flooding" the seal so much. Keith had a batch of these laser cut a few years ago and was kind enough to send me one.

Kapton_spread_open.jpg and


3. A means of stopping the seal from spinning in the carrier. This is advised directly by the seal manufacturer, Best Gasket. At the time Keith documented his fix they were recommending drilling the carrier and adding 3 small spikes. When I ordered my first graphite seal from them in late 2019 they shipped the spikes along with the seal. This time however they appear to have changed their recommendation slightly, and now advise modifying the carrier to take a single 1/16" roll pin, which they still include with the seal, along with a couple things to help you trim the ends of the rope square and not spread the fibers (think of a rope fraying - same principle).

Rope_Seal_Anchors.jpg and


There is another piece of the puzzle as well which is that in order to compress the rope enough to get all the bolts in, you'll need to make a prybar that picks up two of the bolt holes so that you can insert one bolt and then lever the whole assembly into position and insert another bolt.

rope seal carrier prybar.jpg
rope seal carrier prybar.jpg (88.74 KiB) Viewed 26 times


All photos are Keith's, and reposted from his uploads in the Vintage Technology Garage group

-Ben
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PostPost by: gjz30075 » Mon May 16, 2022 11:19 pm

Great stuff, thanks.
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