Lotus Elan

Twincam Rebuild Saga

PostPost by: type26owner » Sat Nov 27, 2004 3:08 am

Rohan,
Since there is no inner race so the shaft is the surface the ball/rollers run on and it is hardened. Could grind it but have no chance of being able to machine it with a cutting tool.

The SKF website does not help here. It demands you know the exact vehicle the part goes on or you're sh*t out of luck finding the item I'm afraid. A part number would be greatly appreciated.
Thanks,
-Keith
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PostPost by: rgh0 » Sat Nov 27, 2004 3:55 am

Keith

I will see what I can dig up in terms of a part number for the SKF bearing it may take a few days as I just had some surgery on my ankle to repair an old sporting injury, so I will be laid up for a few days and banned from the garage.

Unless you have access to a ginding machine, boring out the pully adpator is the way to go

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PostPost by: type26owner » Sat Nov 27, 2004 9:57 pm

banned from the garage.

You have my sympathy for getting issued an order like that! I understand completely. Rest and get well soon so you can resume playing again with Lotus type adult toys.

I ground open the waterpump bearing I just replaced which is a Koyo bearing that DBE supplies. It's a double-ended ball bearing type with what looks like ordinary lithium based grease. There are six 3/16" diameter balls on either end. Really wished I had done this before reinstalling the engine because I would have washed out that grease and repacked it with synthetic stuff instead. Pretty sure the grease is not the problem with these bearings only lasting 50k miles since it still had the right consistancy to be a good lubricant. The broken plastic slinger had allowed the coolant seepage to run along the shaft right to the rear grease seal and there was a crust of rust on the shaft touching and abrading the seal. It appears the grease seal was a few hundred hours away from failing altogether. The more I think about it more I suspect the broken slinger is the real culprit causing the pump to fail. The previous rebuild before this had the rear bearing seal failing in the same way and the outer race had turned blue from overheating when the grease was contaminated and failed to lubricate properly. It didn't help to have the weep hole in the timing cover plugged up with oily sludge either. So far there are no oil leaks this time around.

I have the capability to do the grinding if required. On second thought would just rather buy the already modified integral bearing from the Elan Factory so don't bother looking for the part number afterall. Thanks for pointing me their way.
-Keith
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PostPost by: type26owner » Sun Nov 28, 2004 3:15 pm

IMO leaving the fan belt loose has little affect increasing the lifetime of the waterpump bearing since the real problem is actually oxidation. What would help tremendously is to rustproof the shaft just adjacient to the grease seal without damaging the seal itself. I'm open to suggestions here folks. The carbon/ceramic coolant seal is always going to weep a little coolant so that enclosed pocket is going to be moist from time to time. With the slinger working properly or not there is always going to be rust forming on the bare 51200 steel shaft at some rate. Is there any coating one could apply there to stop it without destroying the grease seal? Bet the damn thing would go at least double the mileage if this problem could be solved. :rolleyes: Installing a higher radial load capacity roller/ball integral shaft bearing would certainly not hurt though.

Would a short blast of WD-40 or some other rust preventative up into the weephole on regular basis be a solution? The hole is big enough to allow the plastic application tube to fit all the way up into the pocket.
-Keith
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PostPost by: type26owner » Sun Nov 28, 2004 6:57 pm

I wonder if the coolant that gets past the impellor seal is sieved out so only water molecules make it through similiar to the way an osmosis membrane operates. If so then adding a rust preventative to the cooling system or a soluble oil is a waste of time. BTW, adding more than a teaspoon of soluble oil per gallon of water is risky because it will dramatically reduce the surface tension and the impellor seal will not be able to contain the coolant. BTDT. :(

Best rust preventative candidate I can find is Boeshield but I've never used this stuff before. I'll call the application engineer tomorrow for info on whether this stuff will attack the grease seal and the elastomer impellor seal which I'm guessing is Buna-N. The website describes the spray can but does not say it has a small plastic tube to insert up in the weep hole and coat the bare steel shaft. Suppose I can exchange the nozzle off another rattle can which does have a tube.
-Keith
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PostPost by: type26owner » Mon Nov 29, 2004 9:07 pm

Changed my mind and have decided to use TC-11 on the bare steel after talking to Bruce Huddleston about his product. He recommended appying four coats at one month intervals while the engine is stone cold to prevent any corrosion. Then once a year after that to be safe. This stuff mainly degrades due to sunlight exposure and will stay put in the dark cavity behind the waterpump bearing most likely indefinitely. Any risk of damaging the elastomers or causing a grease or coolant leak seems minimal at this point so I'm going to go for it and will be the beta test. I know doing nothing will doom me to the 50k mile limit before another failure.
<a href='http://www.tc-11.com' target='_blank'>http://www.tc-11.com</a>

Just cost a small fortune to have the waterpump replaced on my wife's C5 Corvette with 70k miles on it due to this exact same failure. :blink:
-Keith
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PostPost by: rgh0 » Tue Nov 30, 2004 9:20 am

Keith

I have not done the calculations but the 200 to 300 million revolutions the pump does in 50k miles must be close to the fatigue limit of the bearing given its size,speed and loading.

Preventing shaft corrossion and water entry into the grease will certainly extend the bearing life but it may not be as much as you hope.

By the way, my water pump failures ( only 2 in 50 car years) have both been seal failures causing a leak, not bearing failures, though I am sure a bearing failure would have rapidly followed. When I have removed the pump the bearing and shaft has had significant corrosion between the pump seal and the inner bearing seal but this does not appear to have lead to a bearing problem at the time of removal. Hard to tell how long the corrossion has been present for and whether it was just caused in the last few months of pump use before I noticed the leak, however it does not appear to have ever caused a bearing failure.

How much the bigger bearings I have used have contributed to the bearing reliability I cannot really judge. I really should run the bearing life calculations for the standard and bigger bearing to see the difference.

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PostPost by: type26owner » Tue Nov 30, 2004 2:58 pm

Rohan,
If the bearings were overloaded from the belt then one would expect the row of balls next to the pulley to fail first. I've not encountered that situation yet even though that's been my expectation everytime when taking the pump apart for an inspection. The reason I'm hopeful the lifetime of these bearings can be doubled by taking the forementioned corrective measures is one of the things I did upon grinding open the bearing was inspect the balls and races for signs of fatigue. Those surfaces were pristine as far as I could see with a 10X magnifying lense. Very encouraging but not a slam dunk certainty by any means. Even if the grease seal is protected from the huge rust formation on the shaft it will still undergo the normal fretting wear and eventually will become a shield instead of a seal and it's soon toast. Hoping to reach the actual fatigue limit of the bearings before that happens though. Only by performing an emperical test will the true answer be obtained.

The real key to extending the lifetime is to use only distilled water in the cooling system to exclude the introduction of any calcium carbonate and having it precipitate out and then have free floating hard particles of it finally scratching and damaging the sealing surfaces of the impellor seal.

Bruce also mentioned the fact the TC-11 would also protect the impellor seal spring from rusting away. Can't recall if the one I just replaced was rusty or not though. Creep will eventually degrade the spring anyway. He turned out to be a British car nut too but with other marques. :)
-Keith
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PostPost by: type26owner » Tue Dec 07, 2004 4:02 pm

Well I flooded the waterpump weephole pocket a couple of days ago with TC-11 and have driven it for about a 100 miles and there are no water leaks or bad bearing noises so far. Test of preventing shaft corrosion in now underway. :D

On another subject there is an oversight on my part to report if you do the extra o-ring upgrade on the impellor insert as I have described in the past. By eliminating the both the paper gaskets between the timing chain cover to backplate and backplate to engine block there are new places for oil leaks. The three bolts just around the waterpump can have oil weep out from under the boltheads if you don't goop some silicone sealant around those clearance holes through the plates upon assembly. Any leak can still be fixed with the type washer that has a integral elastomer gasket molded into it after the fact. Just found that out the hard way. :(
-Keith
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PostPost by: type26owner » Fri Dec 17, 2004 2:59 pm

Starting yesterday everytime I park the car for a few minutes there's a 6 inch pool of oil which oozes out of the road tube onto the pavement. I suspect the brand new rubber pipe which connects the oil breather box in the head to the engine block has swollen shut already from being exposed to dinosaur oil. My head has the top 7/16" port into the box from the camshaft cavity otherwise the crankcase would be pressurizing. If this is not the case then I've possibly got something horribly going wrong blow-by related. Designing my own aluminum two-piece o-ring sealed spring-loaded oil breather tube to replace that rubber one. I looked at that new rubber pipe and wondered if the spongy elastomer was oil resistant. I think it's a counterfeit. I bought second one at the same time. I'm going to place it in a jar of oil and do a test to see if it's swelling up. I can't heat up though for long periods like it's in the engine.

I'll do the ultimate test to see if the new Hepolite rings are fully seated yet tomorrow. Letting it idle for five minutes then blip the throttle and look for the tell-tale plume of bluish smoke out of the exhaust pipe. There should be none by now and I can switch back over to the synthetic oil.

-Keith
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PostPost by: type26owner » Fri Dec 17, 2004 4:07 pm

Should confess I'm also having a reoccuring problem with the crankshaft pulley leaking oil. This may be self-inflicted though since I'm using what I thought and still believe is a superior seal from Chicago Rawhide #14212 in lieu of the ones that come from the usual sources. It's a spring loaded flourocarbon seal with a Waveseal form which should extend the lifetime a bit if installed correctly to CR requirements. Trouble is the new four inch steel pulley I installed has issues that make it not meet those reqirements. Like the sealing surface had .004" of runout as witnessed by the wear pattern where the seal had it polished it only on one side. What a piece of crap! Fairly certain this pulley would have leaked regardless of the type seal used with it. It is also not hardened. I turned the sealing surface down to get it running true and polished it just like CR warns you not to do to get their seals to perform correctly. Guess what, it just started leaking again the other day. Okay, time for a repair sleeve obviously. I'm seeing some serious quality problems with the parts we're getting now and I'm getting really pissed off.

BTW, the timing marks were in the wrong place for my engine by about eight degrees. This is the second time I've observed the marks being off by this amount and direction and suspect there is a variant timing covers that clock TDC further around counter-clockwise and the pulley marks would therefore be spot on. I had to indent my own marks. Didn't catch this problem when I first assembled the engine years back and man do the Webers spit violently when the timing is retarded by an extra eight degrees on the crankshaft.
-Keith
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PostPost by: rgh0 » Sat Dec 18, 2004 12:33 am

Keith

I have tried the CR14212 viton seal in the past to try to improve the front cover seal but they have turned out to be worse than the orginal red / orange rubber coated original seals.

I think the problem is that the CR seals have a smaller lip that is less flexible and tolerant of runout. No matter how carefully you assembly the pulley and centre the seal mounting hole on the shaft you still have runout in operation due to crankshaft vibration. The orginal style seal stil leaks a little but less than the CR seal.

I still have a new CR14212 seal among my spare parts but will probably never use it.

A long time ago I changed to a press in single piece tapered Aluminium drain tube between the block and head. It presses into the block with a little loctite and seals with an O-ring and a smear of silicone sealant into the head. The Elan Factory makes them or easy enough to make yourself. Just be careful with the hole diameters in the block and head as they vary in size significantly. There appears to be 2 or 3 different diameters that Ford used in the Block and the Lotus heads just have a very loose tolerance. You need make the aluminium tube specifically to fit and press into the block.


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PostPost by: type26owner » Sat Dec 18, 2004 1:01 am

Rohan,
Think a harmonic balancer is called for to dampen the vibes?
-Keith
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PostPost by: rgh0 » Sat Dec 18, 2004 10:43 pm

Keith

I thought harmonic balancers were mainly used for countering torsional vibrations in long crank shafts which is why you mainly see them on straight six cylinder motors.

Not sure how effective they would be in controlling the lateral vibrations in the crank and pulley at the nose of the twincam but worth a try. Ideally you would need to do a proper vibration analysis to determine the nature and frequency of the vibration and then design the pulley to have the right resonance frequency to cancel it out. Not a trivial exercise.

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PostPost by: type26owner » Mon Dec 20, 2004 2:29 pm

If you use a fluid filled viscous dampener type it works in all directions and has some dampening at all frequencies from what I gather. Been checking and there are few to none which are small enough in diameter to fit. Those I did find as possibilities are really expensive. Certainly could build my own and justify the time as well spent if I decide to go down that road. Not absolutely convinced this is the problem though.

Delving back into Chicago Rawhide's technical articles I'm not sure I didn't overlook the obvious and choose some seals that are not up to the surface feet per feet values that the twincam is capable of sustaining. They don't actually provide too much info on this so it's a gray area at best. Time to call for help.
-Keith
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