CJ-5 Got me stumped

Ok guys just so you know Jeep is parked at parent's farm, and I only get to work on her on the weekends when I go home, but went home this weekend, and tinkered a little bit with her this weekend, and fixed the brakes, lights and worked with my problem a little bit. I adjusted the points yet again, a little tighter to .18 and she cranks better, and the run was smoother, but still the busting out at the upper end of RPM range. So Saturday I crunk up to go pick up dad at the tractor shed, and i heard a ping, and all of the sudden the engine cleared up more... I drove up to the shed, and drove hard, no busting out or sputtering! After I got back i held it to the floor, and only when you reach the high end, (which I shouldn't even run at anyway) would it pop... Then I got to investigating, and there was a port on the carb that was open when i got it... I felt over it, and no vacuum, or suction was on this port, so I plugged it off.. Well apparently my ping was the plug flying off. But my question is what the hell is this port for??

 

No I don't, and the vacuum system on this Jeep is nonexistent. I've tried to find stuff on the web about the vacuum system, but looks like I'm going to wind up having to get a manual to figure it out... Plus then I'm going to have to work around a previous owner's "engineering".

 

Not familiar with this variant of the carb, but it looks like it might be an atmospheric vent to the float bowl, perhaps via the air cleaner? Such as the military YS carb needed.

 

Pete thats what I'm thinking, but whoever discarded the old air cleaner system left this open... Not sure if this late of a model had a oil bath or what.

 

I'm no carb expert, but if the float bowl was not free to "breath" I think that definitely might cause weird symptoms. Balancing the interior and exterior air pressure in the float bowl, along with the upper carb throat, would be the idea. Plumb it into the existing air filter to keep dust out, would be my best guess.

Then as Blevisay says, put a vacuum gauge on an active intake manifold port, and tune the idle.

 

Interesting. I don’t know anything about your particular carb but if that port is a float vent your original problem would make some sense because plugging the float vent would prevent the float bowl from filling properly starving the engine of fuel when given a load.