Weber DCNF rebuild; Throttle shaft question

Algar is a top notch shop, by reputation....

 

I still have the original bearings in my carbs and I'm not planning on changing them out anytime soon. I just make sure to regularily pack them with grease. I don't think it's worth my time and hassle trying to change them out, when there's nothing wrong with them. They rotate freely and smoothly and I can't move my shafts east-west at all by hand.

How much free play are you experiencing? If you can easily move the shafts east-west by hand, I would think that would be a little too loose. You shouldn't be able to move them much because the throttle plates have close tolerances to the carb body bore.

The "Haynes Weber Carburetor Manual" book describes removal of the bearings (obviously after removal of all of the rest of the parts first, including the throttle plates):

- Tap the spindle through the bearing with the bearing placed on a vice.
- Re-insert the spindle and drive the remaining bearing from the carburettor body. Remove the bearing from the spindle.

The included diagram in that above manual clearly shows the shaft has a shoulder on it, that the inner race of the bearing rests against, so it's simply a matter of tapping them out. I would be careful when hitting as the shaft isn't a solid piece (hollowed out areas for the throttle plates to slip into). You wouldn't want to bend the shaft! Probably best to use an arbor press...

 

I would say if you have the bearings already, you may as well use them. Even the ones in your carbs right now don't have any play, are you sure they're sealed well enough so there is no vacuum leak?

The easiest way to remove the bearings is to remove the butterfly plates and the throttle shaft. You can then get behind the bearing center to pull it out. When I did mine, I didn't want to mess with removing the plates and having to restake them, so I pulled the old bearings the hard way. First, I pulled the dust shield from the outside of the bearing. Then I jambed a flat bladed screwdriver between the ball bearings and twisted. The twisting motion was enough to coax the bearing out of the carb body a little at a time. Once it was out far enough, I was able to grab it with vice grips to pull it out completely. I found that the outside of the bearings slid out pretty easily from the body -- it was the bearing center that was usually stuck onto the throttle shaft. Some were easier than others, and it was generally a PITA.

An alternative to carb cleaner is to just use soap and hot water in an ultrasonic cleaner. This is what I did and the results were excellent http://f308.blogspot.com/2009/12/carb-rebuild-part-1-of-many.html

 

Maybe slightly off topic but I had bought a set of sealed throttle shaft bearings but have not done any of the carbs. The OEM design has external seal/washers . When you replace this arrangement with the sealed bearings do you still use the external washers. Am I making since here.

 

You probably wouldn't need to put those back on. Certainly put back the small spacers, as you still need those for the linkages and the accel. pump ramps.

 

I rebuilt my carbs including new throttle bearings and I reamed all the lead plugs.

the throttle bearings are not a big deal, it just takes a long of patience to get the plates back in, covering the progression holes properly. I just sat there an tinkered with it until they shut perfectly. On one carb, I had a very slightly bent throttle shaft that had to be straightened. other than that it was just time and patience. A ferrari mechanic taught me a trick to crush the throttle plate screws, using a pair of pliers rather than tapping them with a punch and risking bending the throttle plate.

if you have the carbs off, and apart, best to rebuild them all the way.

 

mine tapped right out, after removing the throttle plates, easy operation. take lots of pictures.

 

2nd that. 5 years ago I bought my gt4 from them - was treated like a king. They had just completed an upper engine rebuild the previous owner paid over 13K for. Tony Deremigio did the work and I can vouch he builds a tight engine. Algar is a first class operation top to bottom.

 

I should have jumped in here earlier but......anyway, I was able to get the bearings off the shafts w/out removing the butterflies. I used the same method everyone uses to take the bearings out/off of the camshaft drive gears. Except little bearings are alot easier: drill a hole in bearing cage & and use a screw head ground down on 2 sides, inserted & turned to grab the races & pull with vice grips, about 5 minutes or less per bearing.
Search the forum & I'm sure you'll find a better description & a Howto.
Bill

 

My screws came right out, but I read that you should use new screws which I did. Are the threads ruining on the throttle shaft? I did f*ck up one of the throttle shafts doing something else, and had to buy a new one, which turned out the be very difficult to find (pierce manifold didnt have any), but I eventually found a new one, not that bad of a price IIRC. I can dig up the location where I found the shafts if you want me to, just PM me. Every where I have read you need to use new screws, they are easily located and cheap.

I am no expert there, so please take this with a grain of salt: I believe the way most people prevent the screws from coming out is to use a punch on the end to spread it out. Doing this you obviously need to support the shaft very well to prevent it from bending. originally, I didnt do this, rather I used Loctite. A ferrari mechanic later told me that was a bad idea, and he pulled my carbs off, and showed me how to take a pair of channel pliers, reach out the throttle plate, adn squeeze the crap out of the screw (which compresses it, physically deforming it enough to prevent it from backing out)

 

I clamped a 6 inch #2 phillips driver bit in the vise, then lowered the screw onto the driver bit, (three hands would help here), then with the screw head fully supported, i used a sharp chisel to stake the screw.

worked fine for me,
chris

 

To my knowledge, yes. For 3 of my carbs, the throttle plates snapped right into place with a little jiggering around. Once settled, they covered the last progression hole just perfectly. On one of the carbs, it didnt cover it, just a slight little moon showing. That was the bent throttle shaft that I wound up replacing.

 

sounds like that would work, albiet a bit more involved than crushing with a pair of pliers.

at the end of the day, i should have just removed the bearing and left the throttle plates in tact.

 

make sure you have a little play in your linkage (ie dont crank the balls up all the way)

Have you read this thread? I think its the best sync thread if you have messed around with your linkage.

http://www.ferrarichat.com/forum/showthread.php?t=55165&page=2