Lotus Elan

Weber Dcoe Throttle Plate Spindle Repair

PostPost by: type26owner » Wed Feb 11, 2004 3:52 pm

How long will newly installed leather seals last in constant service? My experience with these type seals are that they should be impregnated with an oil or light grease as a preservative, lubricant and to seal up any porosity. Any suggestions on a type of oil to use which resists being washed away from exposure to gasoline? Silicone comes to mind put it's a lousy lubricant. Perhaps the seals come already pretreated? They were described to me as being dry though. I could use some help here if anyone has the expertise.
Thanks,
Keith
p.s. I thumbed through my selection of Weber reference books and none of them explain how to identify leaking spindle seals that works at the detection level actually needed. I didn't try dousing them with gasoline like the Weber Manual recommends though.
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PostPost by: bdea » Wed Feb 11, 2004 7:31 pm

I would recommend Lexol, in motorcycle articles I've read, it is the best. Does
not weaken the fibers (leather jackets) and is cost effective. Brad
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PostPost by: type26owner » Thu Feb 12, 2004 3:59 pm

Thanks Brad. That was the clue I needed. It's the Neatsfoot oil which is the key ingredient.

With more pondering on leak checking these leather seals I've realized wetting it with a liquid will probably just seal it up. If propane isn't the right gas to use for leak detection perhaps an inert gas could do it better depending upon the mixture. Part of the problem is the probing technique. Telling if one cylinder is reacting to the probe gas by slightly misfiring or speeding up while the other three cylinders are intermittant is almost impossible for me to audibly discern. Perhaps that's the wrong approach. Going to try wrapping the entire area of the carbs with aluminum foil and flood it with the propane and then the inert gas. If there are multiple leaks then it should amplify the response. That would change it into a go or no-go leak check but not isolate it.
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PostPost by: type26owner » Fri Feb 13, 2004 3:22 pm

Best guess is the useful lifetime of a leather seal is going to be on the order of 5 years if it can't be treated regularly with preservative. Don't know if this is possible yet but I'm going to find out this weekend. Good timing since it's three days.

Car buddy of mine suggested using a smoke generator for vacuum leak checking. That method looks to have the required resolution to find minute leaks. The asking price for the commercial units are out of my price range though. Maybe there is low buck one for the weekend mechanic? If not this ought to be something that can be cobbed together and work just fine. Puffing on a fag is not an option. Yuck! :rolleyes:
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PostPost by: JACKJABBA » Sat Feb 14, 2004 9:12 pm

Keith, I have seen smoke in a spray can being used to test smoke detectors, don't know where to get it but it may be of use to you if you can find it.

Jack
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PostPost by: type26owner » Sun Feb 15, 2004 1:49 am

Thanks Jack,
Since you might be replacing the leather seals right now. Check the seals carefully for defects. Mine were split open around the inner seal hole. Where the leather was formed into a conical shape with a tool. They appear to be easy to fabricate.

The tough part of doing this repair is after truing the spindle to spin with zero runout is to not bend it while reassembling the bearings. The bearing must be drawn into position with a spacer and the 11mm nut.

Smoke in a can is propably zinc stearate. Not sure you would want that in your engine.
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PostPost by: type26owner » Tue Feb 17, 2004 1:46 am

With new leather seals installed it may be necessary to balance the airflow between adjacient throats by twisting the spindle shaft between the throttle plates until it yields. This should only be done once. If it seems this adjustment must be done later on after several years, forget it. It's because there's an air leak. Fix it. It's easy. :D
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PostPost by: type26owner » Wed Feb 18, 2004 4:05 pm

Retire the Unison! The STE brand SYNCHROMETER is the best flow meter I've ever used. Had my rpm meter monitoring the revs and didn't see any dip from measuring the airflow with this tool. Achieved the best idle ever with minutes.

The throttle plates are now repositioned (idle speed screw is needed) because there truely are no air leaks. They are still downstream of the first progressive hole and I've still got the stumble. At the 900 rpm idle position only 1/3 of the downstream portion of the first hole is covered. That's wrong according to the Weber Manual it should entirely cover the first hole. I'm not the original owner of the car so I don't know the tuning history of it but I bet the factory installed these throttle plates. It probably had this stumble since being brand new. Clearly the 79 degree 30 minutes plates are incorrect. Going to install the 78 degree plated this weekend. By my rough calculation that would move the upstream edge of the throttle plate more upstream by about 0.5mm which should be nearly perfect.

Setting the idle speed directly influences this relationship between the throttle plates to the first progressive hole. My target is 900 rpm. Bet I'll have to do some chamfering of the plates edges to achieve that goal.

If the light bulb has finally lit up for me and I'm doing the correct adjustments I'll have to remove and install my carbs only four more times. What a pain but well worth the effort! :rolleyes:
Keith
p.s. The idling is improved because though the same amount of air is flowing. More of it is now directed to flow in the path of the idle mixture passage so the venturi effect is maximized. The improvement is substantial.
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PostPost by: type26owner » Thu Feb 19, 2004 2:45 pm

Left my Elan Manual over at my folks house so could someone please lookup in the specification section the recommended throttle plates used for a S2 (40DCOE_18) and post it here. If it's listed, it will be given in degrees and minutes.
Much Appreciated,
Keith
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PostPost by: type26owner » Fri Feb 20, 2004 3:51 pm

Purchased a pair of new replacement throttle plate spindles as spares and discovered they're made from steel. The originals were brass. Perhaps there is an issue with the flexability of the brass ones? The modulus of steel is almost double that of brass. Noticed on the brass spindles they have been rubbing on the downstream side against the clearance holes on the inside of the carb body throats. That area of the spindles shows scuffing and is worn away by about 0.2mm I'd guess. Didn't measure for this but the clearance holes are probably worn also. The direction indicates it's been happening on throttle plates closed overruns. The manifold vacuum would go nearly to 28 inches Hg and propably caused the brass spindles to deflect under the load. If that center coverplate is not sealed up air tight then that provides an even bigger opening for the wrong source of air to supply the idling.

I'll be installing the new steel spindles tomorrow.
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PostPost by: JACKJABBA » Fri Feb 20, 2004 5:58 pm

It makes you wonder why Weber now only supply the pump lever cover plate with a hole in it for all the DCOE carbs. :angry:
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PostPost by: type26owner » Fri Feb 20, 2004 8:57 pm

Jack, please show me the version of a DCOE that has a hole in that coverplate. I can't find even one.
<a href='http://www.piercemanifolds.com/weberexplode.htm' target='_blank'>http://www.piercemanifolds.com/weberexplode.htm</a>

Do you have a reference in any tuning book which explains why a hole is a requirement?

The folks who sold me the official Weber Tuning Manual could not answer my questions where the manual made a general statement and I needed to know the specifics. It was obvious to me they had not read it.....
Regards,
Keith
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PostPost by: JACKJABBA » Sat Feb 21, 2004 10:00 am

I went to Motorscope in Northallerton, they do rolling road tunes and sell loads of performance parts. When I was explaining to the guy what plate I needed, he got a new DCOE carb off of the shelf, It looked very big probably a 48 and I showed him the pump cover plate. It had a hole about 10mm the middle. I said thats the one I want but without the hole. He said they all come like that and that it was just a dust sheild. I then called Gower and Lee (01923 247300) and they said thay had some in for the 40. He emailed me the next day, as when he checked them, they had the hole. He cantacted Weber and they confirmed that they all now have the hole in them, and that any spares that are now ordered will have the hole. Apparently its for mounting to something.

I will try and find a website with a pictue of a carb with the hole.
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PostPost by: types26/36 » Sat Feb 21, 2004 6:53 pm

Keith,
My Lotus Workshop Manual does give the specs for the throttle plates but I have my S2 carbs off (DCOE 18) and the throttle plates are 79 degrees 30 mins.
I also have a DCOE 151 and as Jack says it has a hole in the inspection plate which is 9mm dia. the throttle plates in the 151 are 78 degrees 0 mins.
Regards Brian.
Brian
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PostPost by: type26owner » Sun Feb 22, 2004 4:04 am

My Lotus Manual didn't mention the angle of the throttle plates. Installed the 78 degree plates and new steel spindles today. Got my fingers crossed that blasted stumble is gone now. Now at the approximate idle speed screw position of it idling the downstream edge of the first progressive hole is perfectly aligned with the downstream edge of the throttle plate.

The new steel spindles were missing the rollpin hole for clocking the accelerator pump lever. It had been cross drilled by hand originally and was crooked to the spindle by about 5 degrees off of perpendicular. Had to exactly replicate the wonky hole in the new spindles. A milling machine is required.

The 78 degree plates reduced the full stroke of the accelerator pump piston travel from 10mm to 9mm. Measured this with the original spindles still installed. Betting that's okay.

Bet the newer carb designs have inner shaft seals of some sort. Would be a good reason to use steel for the spindle is they incorporated ferrofluidic seals there. The steel would be needed to direct the magnetic field flux into a torodial shaped field needed for such a seal. Just a wild guess though since I've only seen the outside bits of that type carb. :unsure:
Regards,
Keith
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