stumble when asselerateing

[Brendan]

my 36 pickup has a 35 21 stud motor with a 97 carb. also has a 36 distributer. it has started to stumble when under accelerating, only when I take off from a stop sign. last night I came home and loosened the brake in the distributer, that seemed to help some what any ideas please help

sorry about the other photo

[f1builder]

i would check the fuel supply first. could be blocked or change filter.

[Capt Kirk]

First place I'd look is at the accelerator pump on the carb. When was the last time the carb was rebuilt? I'm not buying the filter idea...that would present itself at other times as well...such as highway speeds when the fuel flow rate is at a maximum. Ignition is the next place I'd look. Check engine vacuum and see what you've got.

[Brendan]

carb was rebuilt about 3 years ago, newer fuel pump and fuel line . how long would you get out of a set of points before they need work . I have about 10 thousand miles on the motor. I put in a rebuild diving bell distributor. the pickup has been trouble free for all of thim

[Pete]

The first thing to check is, look down the carb WITH THE ENGINE OFF and work the throttle. Watch to see if there is gas squirting from the accellerator pump nozzles. There should be a healthy squirt and it should be equal on both sides.
Next check the points for gap and pitting.

[Capt Kirk]

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I've got this one and only flathead so I don't have a lot of experience with them but growing up all I drove was carbureted engines. Drove my 63 bug during high school and into Jr college. When that car would stumble right out of the gate, but run good the rest of the time, it was always the accelerator pump. Does your vehicle sit for long periods (like all winter). If so, this could probably dry out things in the carb and cause problems. If you're at a stop light and you stomp on the gas, the first thing that happens is the butterfly opens and there's a jet of added fuel. The rest of the engine is just dealing with what just happened micro-seconds later. If you don't have that blast of fuel from the accelerator pump...it's going to stumble. I'm just going on what you said...I'm assuming the thing runs great during the rest of your driving around.

[Capt Kirk]

Adding to what Pete said, the fuel needs to spray into the carb almost immediately after working the throttle lever. I've seen accelerator pumps very weak in the beginning and then work correctly past a certain point. These accelerator pump bores wear more at the upper end due to daily driving...the lower end doesn't get used that much.

[Brendan]

i will check that out tomarrow, in California my cars don't sit very long, I think the longest it has sat was a month or two

[Brendan]

it dose not rain hear...LOL I think it will never rain hear again!

[Capt Kirk]

Brendan...I was brought up in Weed CA. Not sure what it's like there now but back then, up in the mountains, we didn't have a problem with rain and snow. I feel for you! I'm in MI now...too much water. Sorry man.

[Willit Stop]

Hello neighbor(I'm just up 101 from you).Look on the passenger side of the carb near the base.There is a linkage rod that activates the accelerator pump.There are two studs that the rod can hook to.One marked "S"(summer) and one marked"W"(winter). Move the rod to "W",the one farthest away from the pivot. It will give a little more gas when you step on the pedal.If it improves, replace the pump washer and move it back to "S".