52 flat head mid throttle bog

[hernk1]

hello everyone.  I just recently purchased a 52 dodge truck. I have been working on it for a couple of weeks it has been sitting in barn for 30 yrs. I got it running smooth after fighting stuck valve.  Now I discovered a bog about mid throttle.  I am not familiar with this old stuff but loving every minute of it.  If I ramp it up real slow it will get to high RPM but if I stab it it will die. not sure where to start any help greatly appreciated.

[NiftyFifty]

Welcome to the site! I guess first off we would need to know what you've already done, have you put new points and condenser, new plugs, new wires, cleaned or rebuilt the carb? All the stuff that needs to be addressed before really giving any diagnosis. It sounds like fuel too me, but always tought to say. Have you tried adjusting the mix screw on the carb?

[TodFitch]

Sounds like the accelerator pump leather in the carburetor may have dried out.

[hernk1]

so far I have changed the condenser, points, plugs and clean the carb I have not tried playing with the fuel mixture screw it is two and a half turns out.that leather piece in the car seemed to make a good suction sound but not real familiar with what it does or how it should operate

[BigDaddyO]

Mixture only effects idle. Accelerator pump.

[Reg Evans]

Look down the throat of the carb while you work the throttle linkage. If a stream of gas squirts down the throat that's not the problem. If it doesn't....there's your problem.

[jeffsunzeri]

Like everyone's mentioned, your problem is almost certainly the accelerator pump.

I'll assume you're not familiar with carburetors, so a little explanation is in order.

When the throttle is opened quickly, the carb gets too much air too quickly. To compensate for the excess air, the carburetor has an "accelerator pump". The accelerator pumps mission is to add an extra bit of fuel just as the extra bit of air is being admitted, and prevent the lag you are experiencing.

To see if your accelerator pump is working, do as Reg mentioned: remove your air cleaner, open the choke, and look down the carburetor as you move the throttle from closed to wide open, fairly quickly.

If you find it has failed, carburetor cleaning and rebuild is in order.

Edited May 14, 2015 by jeffsunzeri

[hernk1]

if I do not see a squirt of fuel when accelerating quickly what do I look for to fix the problem

[Plymouthy Adams]

the accelerator pump in the carb is the plunger that moves within the barrel inside the float/fuel chamber and has a leather cup that is usually spring lined for equal expansion.  When the carb sit without fuel, the leather will dry and shrink...you can often salvage the lather by removing and soaking overnight in a oil and adding new life to the leather...

[Merle Coggins]

And after following Plymouthy's instruction on the accel pump cup, you may need to clean out the passage that runs from the plunger barrel up to the nozzle at the top of the carb. I had that problem with mine. I had to keep cleaning and running a small wire through the ports until I could get gas to pass through.

 

Merle

[hernk1]

So I looked and I have a dribble not a squirt. Should it be a definite squirt?

[Plymouthy Adams]

steady thin stream for the throw of the plunger...

[Reg Evans]

You can remove that plunger without even removing the whole carb.  Just remove the 4 screws and lift the lid. You will need to remove the little curved linkage from the bottom of the carb that attaches to the plunger arm. The plunger is right there. You have to push the slotted washer down and turn the plunger shaft to release it from the washer.  Now you can replace it or try oiling it up over night.

[hernk1]

Any special oil or is motor oil ok?

[Reg Evans]

Motor oil should do the trick.

[HanksB3B]

This is always good to have around

Hank 

[hernk1]

so I looked at the plunger. when I operate linkage with the top cover off  the plunger goes down really slowly. (there is a space between top of spring and arm).  If I push plunger down manually it squirts out gas threw the hole it is suppose to.  not real sure if I put something together wrong after my friend and I cleaned it.  I am guessing that the spring should push up against the arm?

[Jeff Balazs]

You can try testing it by filling the float chamber with denatured alcohol and putting the top back on. Then simply operate the throttle and see if you get a good stream. If all you get is a dribble then you may have a clogged passage or the check ball may not be seating. Hope this helps.

 

Jeff