Question for the carburetor experts

[Unwroolie]

Rebuilding the Weber WFB 4-bbl on my 7.4l. I've done lots of automotive carbs including Webers, but this one has thrown me a curve.

The manuals all refer to a "spring and check ball" or "check ball and weight" under the accelerator pump nozzles. Upon disassembly, I found neither - just a smaller version of the inlet needles. Can't find a reference to this particular setup in any of the maintenance or parts manuals.

Being that this was a Sierra reman carb, I have my doubts. Is a small brass needle valve the current/correct arrangement for the accelerator pump or did Sierra mess that up?

Anyone who has had one of these apart recently please advise.

 

[hughespat57]

Try looking up your engine/carb here.
https://www.carburetor-parts.com/Marine_c_29.html

I used them for my rebuild kits, they have good documents and youtube videos

 

[markrsimon]

Here is what was in my Weber carb - as it pertains to the accelerator pump. Not sure what nozzles your referring to. The rebuild kit came with a new pump, not exactly the same, but similar enough. Definitely no check ball there, or anywhere else on the carb that I recall. I believe mine is a 9772.

 

[HawkX66]

I just rebuilt a Weber 4bbl two weeks ago for my 7.4L. There should be a weight and check ball no spring. It's under the accelerator pump nozzle. Center top of carb in my below pic. You should hit up Youtube and watch a couple of guys rebuilding them. It'll show it pretty clearly. Mine didn't have the weight, only the ball. I'm sure the last "rebuilder" forgot to put it in or lost it. The cheap rebuild kit I got didn't have the weight, so I had to make it out of an extra needle the kit came with.

 

[Unwroolie]

Here is what was in my Weber carb - as it pertains to the accelerator pump. Not sure what nozzles your referring to. The rebuild kit came with a new pump, not exactly the same, but similar enough. Definitely no check ball there, or anywhere else on the carb that I recall. I believe mine is a 9772.

The accelerator pump discharge nozzles sit between the primary venturies. Every carb that I've worked on has some type of check valave that allows fuel to travel from the pump to the venturies but prevents fuel/air from being drawn back into the pump when the plunger is released. It's usually a ball and spring but apparently the 8867 carb uses a needle valve.

 

[HawkX66]

The accelerator pump discharge nozzles sit between the primary venturies. Every carb that I've worked on has some type of check valave that allows fuel to travel from the pump to the venturies but prevents fuel/air from being drawn back into the pump when the plunger is released. It's usually a ball and spring but apparently the 8867 carb uses a needle valve.
View attachment 107582 View attachment 107583 View attachment 107584

Awesome pics. Good to know. Everything I was seeing for my 9780s carb was talking about the weight and ball so that's what I focused on. The needle valve makes more sense in reality... That needle is what I cut down to use as the weight for my ball.

 

[Unwroolie]

When all else fails, go to the source. Edelbrock owns the Weber line, and after a brief search of their website, I found the following regarding the accelerator pump:

"Next test is to see if the discharge check is working. There may be a check ball with a small check weight above it. Some AFB's, or Weber Marine use a check ball and a spring. Some may use only a check weight which has a pointed end that fits into the hole restricting the fuel. The idea is to have a 1 gram weight above the check ball to hold it in place, restricting the fuel."

That's the first (and only) reference I've found that mentions the pointed weight. So out of curiosity I weighed the needle that came out of mine - 1 gram exactly.