I am leaking vaccuum from my throttle linkage on primary 3X2 carb. Can I fix the linkage myself, or do I have to send it somewhere?

 

This is a very common problem and it's caused by the return spring configuration. There are a few machinists that can re-bush the throttle bodies, and there is an outfit affiliated with Holley that makes the whole carb like new somewhere. I'd look around locally for machine shop with an old timer that remembers how to do it. I used to have Q-jets and Thermoquads done all the time, but it's getting to be a lost art.

Hans

 

By "linkage" I assume you mean the throttle shaft.. where it goes into/through the base of the carb (throttle body).

The throttle body & shaft did not have a bushing when new. The fix is to disassemble the carb & throttle body, remove the disc retaining screws & discs, remove the shaft from the throttle body, bore out the throttle body and press in a bronze "bushing", re-assemble.

The centerline of the shaft and the 3 retention holes it rides in must be kept perfectly aligned or the throttle will bind. There is a special piloted reamer for this job to keep the centers properly aligned.

The disc screws are "peened" over by Holley. You cannot remove them without destroying the shaft threads unless you develop your own process for first removing the peen. I do it with a dremel.
I re-attach them with medium strength thread lock.
Re-centering the discs upon re-assembly is an art.

As originally configured, the throttle shaft rides directly on the soft metal of the throttle body. Because of the return spring design (as stated above) the throttle shaft wears the throttle body in an egg-shaped pattern, and the throttle shaft is also worn. This creates excessive clearance between the shaft & the body, which leaks air (vacuum leak).

If the carb has not been previously repaired in this area, then the fix is as described above. If it already has been "re-bushed" (mis-nomer), then you can have difficulty getting it repaired due to differences in tooling requirements.

For example, if I come across a throttle body that already has a bushing in it with an OD larger than my own bushings, I cannot easily re-bush it, and I don't spend time on it.... although possible, not worth my time to repair it. I would have to charge "real money". Might as well buy a new carb.

Long term care... after the repair, redesign your linkage so the throttle return spring pulls in direct opposition to throttle movement, instead of using the shaft/body as a "pivot". I designed a bracket for exactly this purpose for the 427/400, but its application depends on whether or not you have the OEM A/C solenoid bracket.

I just repaired a throttle body for a 427/435 center carb.
The outside carbs are supposed to be "sloppy" to allow the vacuum controls to open them easily. There is no spring/pivot action to wear them egg-shaped, so they're generally in good condition. The center throttle body and the end throttle bodies are not interchangeable.

 

Tom454
I do have the OEM ac bracket on vette. Do you sell your new spring design? What would you charge to re bush by throttle shaft?

 

Holley will restore carburetors. The phone number can be found on the web site. They are located in Bowling Green, Ky. (An easy location for Corvette owners to remember!). If I'm not mistaken they wanted $600 (minimum) to restore a set of 3X2 carbs. I forget the exact details of what the $600 includes, but I think it includes replating and replacement of certain designated parts. I'm missing a choke assembly on one set of 3X2's and they would include a new choke assembly, but that was extra.

 

I'm not a "vendor" here.... just a peon.

I can send you pics of the spring bracket.. I give them away.
pm/email me.

 

Tom, you mention that you do these yourself. I'd be interested in to know exactly what size reamers and bushings you use, and what their original application was. Are these bushings readily available? I lost my machinist that did these to a heart attack a few years ago, so I want to develop the skills to do it myself. I have a bunch of old junk carbs to practice on!

Hans

 

Hi

I would also be interested to see pics of this bracket design for my 68 Tripower. I installed the spring as I think it was originally, to the front fuel line.

Günther

 

I used to own/operate my own machine shop and bought my tooling 30 years ago… from Lacey-Williams Supply in NJ... a product marketed by K-Line tools. It appears to have been discontinued.

The "set" included a piloted reamer, 3 ball broaches, a bushing driver, a cut-off tool and a nylon brush.

Their bushings are a "split" design, and because of this, they do not have a specific OD. They are a press fit. Once the throttle body has been reamed, their special tool/driver is required to insert them into the throttle body. They are thin walled so a minimum of material is removed from the throttle body to avoid splitting the casting or cutting into cast passages.

The reamer and bushings are a matched set... their bushings only work with their reamer.

I can measure the reamer for you, but without the rest of "their" kit and bushing inserts, you really cannot use that diameter.

Maybe somebody else is sellng the kit under a different name.

KL9315 is the discontinued K-Line 5/16" kit number.

TriPower requires the 3/8" kit.

 

Here's one...

http://www.supercooltools.com/html/ZA05/index.html

I have no experience with this one.

 

I would like to see pictures. It sounds like what I need. Can you ship me one. I can pay shipping.
Mark PERRY
P O BOX 1142
BYRON, GA. 31008
THANKS..


QUOTE=Tom454;1560554441]I'm not a "vendor" here.... just a peon.

I can send you pics of the spring bracket.. I give them away.
pm/email me.[/QUOTE]

 

Thanks Tom, that looks like the one I'll try.

Hans

 

[/QUOTE]

pics sent

 

pm sent

 

Is your leak on the driver side, passenger side, or both? The wrong base gasket will give you a pretty good leak on the passenger side near the throttle shaft.