Weber throttle shaft bearings

I missed the recommendation to thoroughly repack the bearings when cleaning my 40 DCNF carbs a couple years ago. Even the Weber manual published by Haynes barely mentions greasing the bearings, advising to "lubricate the bearings with a little grease".

But Mike at Pierce Manifolds took the time to explain to me the importance of either greasing the bearings to seal air leaks at the throttle shaft, or better yet, installing sealed bearings. He explained my 308 symptoms as if he had just gotten back from a test drive (lean surge and uneven running at one-third throttle or less). I opted to buy the sealed bearings and rebuild kits to install as I don't want to revisit this job anytime soon.

So I'm most of the way through the project and wanted to share this photo of an original bearing just pulled from one of my carbs today (left), and the new sealed replacement (right). It is pretty apparent that air can suck right through and place inordinate demands on the brass sealing washer.

Hope this helps somebody in their quest for a perfect running 308!

Jeff
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thats a fun project, keep us posted Jeff.

are you pulling the throttle plates and the shaft, or just pulling the bearings?

 

As I am putting a kit through a spare set of carbs now and am steering clear of messing with the shafts and bearings, i wonder whether a soft, thin washer could be added at either end of the shaft to reduce the amount of air able to be sucked through the unsealed bearings, in addition to packing the original bearings with grease.

maybe a fibre washer? nylon? rubber?

any ideas?

 

I have removed the throttle plates, shafts, and bearings. So far, so good. The dicey part is getting the screws out of the throttle plates. Use your very best screwdriver. I used a dremel tool with tiny cutting wheel to cut off the exposed threads first. With firm, steady turns of the screwdriver, they all came out. I have finished three so far. Throttles snap back fully closed.

Guy, to use a seal like you describe, you'll have to disassemble all the way down to expose the bearing. If you don't want to go further, grease is the best solution, though a rather temporary one. There is a brass sealing washer that covers the bearing and a wavy washer that pushes against it. If you replace that with a softer material, it won't last long with the twisting of the throttle shaft.. The sealed bearings from Pierce are just $9 each.

 

I think you are doing the right thing, but I just dont dare to start playing with the screws off the throttle plates and worry about bending the shafts with my hamfists!

 

If you haven't put the screws back in the plates, do that carefully as well. the biggest risk to upsetting the plate geometry is when you spoil the threads. the punch method is risky, an old fcar mechanic showed me the channel lock method which I have posted before. Great way to spoil the threads but not impact the plates/shaft.

 

Geno,

Yes, thanks, that it is exactly what I did. It is a little nerve wracking dealing with the screws, makes me wish I'd gone to dental school for the experience!

Jeff

 

Does anyone know where I can find a throttle shaft for a 1965 275gtb Weber carb?

 

First call would be to Pierce Manifolds.

 

Guys -

after searching and searching, I can't find an answer, so I'm bumping this old thread. I have a low idle miss, and I'm about to pull carbs and rebuild them. While I'm at it, I thought I'd do the sealed bearings as well. I didn't plan on pulling the throttle shafts though. Can the bearing replacement be done without pulling the shafts? Any install tips or tricks?

Thanks,

Ken

 

The main thing is to not twist, in any way shape or form, the shaft from end to end, otherwise the throttle plates will not properly seal inside the throat. Things what will twist the shaft include taking out the throttle shaft screws, not properly holding or supporting the shaft when loosening the lock nuts and associated parts on each end and removing the shaft from the bearings that are seated in the carb body.

Luckily, there is a manual and procedure for each of these things. Read, study, and re-read the steps and procedures. If you run into something that is tight, don't force it. think it through and if you have to use some force, just be sure ti will not deflect or twist the shaft.

Here is link to Chapter 13 (DCNF) Haynes Weber Carburetor Workshop Manual. Its probably best to print out each page. Overtime i have seen a copy of this o the internet, the pictures are dark and not detailed, but its enough to get by and in conjunction with the narrative, the procedures are outlined. Be gentile and go easy...and remember with 4 carbs there is 4 times the chance to screw something up!

I read through the whole chapter several times and studies the diagram before I took mine apart. Everything went smoothly. I would also recommend to take pictures, and make notes, especially regarding the order and parts on each end of the throttle shafts, (that's 8 ends, each with a different tab and both narrow and wide spacers.) See the picture below. I used plastic boxes to keep the parts separate and each carb had it's own box. Check to see if all the jets are the same and what sizes you have. Here's the link.


Haynes Manual - Weber DCNF 246 308 | How a Car Works

Throttle shaft disassembly starts on p. 8 #30-42 There is a specific way to remove the shaft from the bearings and the bearing from the shaft. i recall that the bearings on one side was a bit looser that the other. Once the shaft is out, the bearing has to be removed from the other end

Throttle shaft assembly is on p. 8-9 #3-5

Use new throttle plate screws. I was told by a reputable carburetor rebuilder that the throttle plate screws are lightly screwed into the shaft so they can just barely move, then the end parts and locknuts are put on and tightened, (see procedures above) thereby allowing some fine adjustment of the plates in the barrel. Make the necessary adjustments regarding plate fitment and use loctite to secure the screws. (I tightened one screw on the shaft to hold the plate, removed the other screw, put the loctite on and repeated with the other screw.) Re-adjust as necessary. I also light staked the screw ends using a chisel to swage the end. This is where the real danger is in twisting the shaft. Support the end of the screw to provide a very solid base. It helps to have another person hold the whole carb body while you strike the screw. One or two good blows is all that is necessary.
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Yep, I own that book. I guess what you are saying is, the only way to remove the bearing is to remove the shaft.

Well - that sucks.

Yeah - once I get the air cleaner off, I plan to take a lot of pics and document, document, document..

 

Where might I find the details of channel lock method.

 

PN for those looking is SKF 607-2RSH/LHT23

 

with the screws tightened down, instead of using a punch on the end of the screw to deform it and prevent it from backing out, you take a pair of large channel lock pliers, with side of the plier on the phillips head, and one side on the other end, not touching the throttle plate, and squeeze screw until the end deforms, thereby preventing the screw from coming out. Follows the same logic as punching the end, but with this method you never touch or exert any force on anything but the screw. You essentially just smashing the screw, and it take surprisingly little force to do so.

 

Some time ago our Canadian GT4 friend Peter designed a neat little tool for Rob Garven for pulling the bearings without removal of the shaft.

Post 33:
http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/289637-weber-carbs-40-dcnf-101-a-2.html

 

That is a very cool little tool. How do I get this fantastic little tool?

 

you could contact Rob Garven. I believe I know, but I'm not quite sure, which Fchatter named Peter made it for him.

Best Regards
Martin

 

I used these extractors for my outer cam pulley bearings and will adapt the 5mm inserts for my carburettors in the future.

225000 - Twin Pull Mechanical Pullers | Toledo
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I have no bearing within reach, but I think the min. spread of the puller is still too large, since the centerline of the balls is less than 20mm.

Best Regards
Martin