258 Bogging in floating conditions

[Urban Gear Head]

First time poster, long time reader and fan.

So here is the issue; Jeep was running fine and slowly a "bogging down" issue became present. The jeep is rough to start ( could be due to not setting up my electronic choke during new carb install) but once its going it seems to bog with light throttle. However if I really get into it the jeep seems to buck and bog and then take off like it should! Timing is set at 10*btc (nutter, msd) and I have tried to adjust the distributor vac with an allen wrench but it doesn't seem to catch or turn. The fuel filter is new, and vac leaks have been ruled out (i think). Carb is a motorcraft from the ebay guy that sends a short book with his carb sales. Installed a year ago with gasket maker and correct gaskets. The bog issue is extreme during initial warm up but still present and scary when pulling into intersections. Any suggestions would be greatly appreciated!

 

[Lumpy Grits]

:ww:
Knowing MC carbs and their issues, my first though is a vacuum leak at the carb's base.
LG

 

[Hedgehog]

Why not try this. You know you didn't set the choke up properly, who knows what else isn't correct. You also know that the engine isn't running correctly. Start over again. Pull the carb. Clean it up, including the partially plugged low speed jet(s) and the faulty power valve. Do like I did last week and get the proper phenolic base plate, the base gasket and top gasket. ..... also replace the fuel filter with the proper return fitting. Honestly, do it as correctly as you can the first time. Sorry to be so blunt. It seems like we've been getting a lot of these posts lately. Part of the starting troubles related to cooler temps, but almost inevitably there is an, "I didn't do this", or "I didn't hook up that" before the full story is told.

 

[caveman]

After checking and fixing anything that Lumpy and Hedgehog mentioned, And if it still does it, Check the accelerator pump on the carb. It sounds like it may not be getting enough gas.

 

[Bent]

I'm chasing a similar issue. Stumbles under acceleration, then runs well under wide open throttle. This issue developed slowly. I thought I had a vacuum leak at the base gasket or adapter gasket. Replaced the gaskets, same issue. Mine is a manual choke. I have also adjusted the idle mixture, changed main jets (46 to 49), reset the float level, changed the accelerator pump rod location, reset base timing at 10 degrees BTDC and verified the vacuum advance is operating.
Recently after shutting the engine down and taking the air cleaner off I noticed a few drips of fuel from the from the discharge boosters. I ran the engine again thinking the excess fuel was coming from the accelerator pump nozzles. But, the second time I could see that it was dripping from the boosters.
This makes me suspect the power valve is releasing too much fuel into the metering circuit under low manifold vacuum. I'm going to pick up a power valve set to open at a lower vacuum level or install a power valve plug for trouble shooting.
Another cause may be a bad gasket between the carburetor body and the discharge booster/accelerator pump nozzle unit.
Let us know what you find!

 

[Bent]

New power valve fixed my issue. No more stumbling or bucking.