Lotus Elan

Rope Seal friction

PostPost by: Quart Meg Miles » Sat Apr 01, 2017 4:51 pm

At last got everything inside the block and torqued up. The crank a little stiff on the rope seal but not too bad (edit: in fact 3-5 ft-lb after removing sump again), so I fitted the front cover and finally the sump, having fitted its rope seal a week or more ago. The block seal was flush with the block and the sump's seal 0.020" (0.5 mm) proud at each end, both fitted into Wellseal in their grooves and smeared with Graphogen on the crank face. I trapped the cork sump gasket between the rope ends otherwise I would have to cut the cork around their shape. With the sump fitted and only torqued to around 5 ft-lb the engine is stiff and takes 10 ft-lb torque to turn and a little more to start rotating. I don't remember it being that stiff before and would normally have just smeared them with oil. Now I remember, as the thread "LOTus of US head bolts" recounts, I had soaked the rope seals in warm oil (it cooled, of course) over a period of 24 hours prior to pushing them into their grooves.

So is this normal and should I just continue assembly? If not, why is it so stiff: has the rope swollen with the oil or hardened after being left for a week? Should I remove the sump, cut the cork pieces from between the seal halves and refit the sump? Or what? I'm so close to a working car again I'm seriously frustrated that a routine bit of assembly seems to have gone wrong.

Any advice gratefully accepted, thanks.
Last edited by Quart Meg Miles on Sat Apr 01, 2017 7:17 pm, edited 1 time in total.
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PostPost by: el-saturn » Sat Apr 01, 2017 5:39 pm

i'd say: take the sump off again and cut a mm off and use a tiny bit of rtv in the corners: PLUS graphogen isn't as good as reg. oil! there's a bunch of better experts here AND i switched to 6 bolt crank 5 years ago. with the type of friction you're talking about it may get very hot! sandy
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PostPost by: Quart Meg Miles » Sat Apr 01, 2017 8:47 pm

You could be right about oil, Sandy. I'm convinced I read "smear the seals with Graphogen" but can't find it again; it says oil in Wilkins and that's where I thought I'd seen it. He seats the seals on RTV whereas I used Wellseal.

I couldn't find RTV locally so am using Loctite MR 5922 which is black and I hope is the same.
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PostPost by: englishmaninwales » Sun Apr 02, 2017 9:34 am

I found this problem when I last fitted a 4 bolt crank seal. Despite following all the rules, it was very tight indeed but freed up quickly after the engine was run. But as it still leaked oil, although alot less than before, I converted to a 6 bolt crank. On inspection rope seal looked like it had got quite hot.
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PostPost by: Quart Meg Miles » Mon Apr 03, 2017 6:13 pm

I decided to fit new seals, having found two spares, but noticed the older one was much smaller than the newer one which was like the ones which are giving the problem. I appealed to St Wilkins, who declared he hadn't overhauled a 4-bolt recently, and he managed to find an old set "in his grandfather's chest". The photo below shows the difference and I am already soaking my old one and one of Wilkin's ready to install tomorrow.

rope-seals-153_4863.jpg and
Modern, my old, Wilkin's two olds

This might be well the reason for my excessive friction and I will post with the result!
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PostPost by: Craven » Mon Apr 03, 2017 6:54 pm

Hi,
If you look carefully at the accepting grove you will see it?s a wedge shape, using a depth gauge check the depth against the seal profile. If the seal is not forced to take up this profile it will at first be to tight then quickly loosen and leak.
FWIW
Ron.
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PostPost by: Quart Meg Miles » Thu Apr 06, 2017 10:02 pm

Success! With two of the original seal types fitted the engine feels normal and measures around 5 ft-lb to turn and the piston drag is very apparent.

Following Ron's posting I popped old and new style seals into the housing groove and photographed them.

rope-seal-old-153_4866.jpg and
Old style
rope-seal-new-153_4864.jpg and
New style
They both fit snugly and easily and the extra protrusion of the new one is clear. BTW, to push them well into the groove use an old main bearing shell, it's the perfect size and comfortable!

If I still have enthusiasm after getting the car running I'll try shaping the new type in some sort of mould.
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PostPost by: rgh0 » Fri Apr 07, 2017 11:08 am

Keith of Sidedraft_central and vintagetechnologygarage yahoo groups swears by a rope seal gasket from a company called Bestgasket for his rope seal Elan and twin cam engined racecar. He uses their graphite rope seal part number 6382S which is the seal for a Pontiac V8 428 - 455 1968-76.

I have not built a rope seal engine for many many years but if i did one now i would use this sort of graphite rope seal. I have used similar graphite rope seals in a lot of process plant equipment and it sure seals better and last longer than the original style seal material

Keiths quest for a carb, rope seal twin cam that runs like its fuel injected and does not leak oil is a magnificent obsession.

cheers
Rohan
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PostPost by: Quart Meg Miles » Fri Apr 07, 2017 9:07 pm

rgh0 wrote:Keith of Sidedraft_central and vintagetechnologygarage yahoo groups swears by a rope seal gasket from a company called Bestgasket for his rope seal Elan and twin cam engined racecar. He uses their graphite rope seal part number 6382S which is the seal for a Pontiac V8 428 - 455 1968-76.

cheers
Rohan

Maybe next time, Rohan, the block's already in the chassis.
Meg

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