Carter BB Carb Question

[grey beard]

My engine starts and runs just fine. It has plenty of power for its size. But when I cruise at a steady speed, it runs rough and bucks a little. I can also make this happen in the shop. At a steady 2000 rpm, it runs rough. This is the only problem I have. Otherwise it runs and performs just fine.

My understanding of carb circuits is that this is the main metering circuit at work at this speed. What's the remedy? Drill out the main jet? Find a larger main jet? Is this a problem any of you have encountered?

I look forward to your wisdom.

Thanks

[MBF]

GB-what do your plugs look like? Is she running lean or rich? Is the float level adjusted properly? Has the carb ever been rebuilt? Fuel pump getting air someplace? Slow valves? Mine coughs at idle sometimes and seems to be vaporlocking after getting a good dose of heat sink from sitting after a long run. Its always somethin' aint it-but that's what makes these old trucks fun. Mike

[Young Ed]

Mine ran like that twice. One time I replaced the vacuum advance. Then another time I slightly raised the float. I think I've finally got it to where I can leave the carb alone!

[grey beard]

Whilst diagnosing for another problem in the past, I pulled the carb top and set the float level with a steel rule right onto specs from the shop manual. During the engine overhaul, I put a new kit in the carb. Everything is clean and nice inside.

This problem only exhibits itself on a cruise situation. As soon as I accelerate even slightly it disappears. Seems like a lean running condition to me. Guess I could try a little choke when this happens to see what that does. If that solves the issue, then I know it's running lean. Mebby I'll need to increase that jet size somehow. I have a few core carbs. Mebby one has a larger main metering jet . . .

Any other thoughts, y'all zen masters?

[Tom Skinner]

Dear Grey Beard,

Have you tried hooking up a Vacumm Gauge and setting the Mixture Needle

that way? Of course a little dirt in the Carb could cause trouble also.

I have a Fuel Pump that works its bolts loose slowly - very slowly,

when I tighten it back up with a 1/2" Socket and tighten the Carb Body screws all my troubles go away. These old Motors just need a Lot of TLC.

Good luck running down your problem, I'm sure you'll find it.

It could just be crappy gas from a dirty Gas Tank Vessel???

Tom

[OLD DODGE]

Just a thought, since you were recently discussing setting the distributor timing. The cruising condition you describe would be the place you would get your maximum peak for the mechanical and vacuum advances combined. Your rpms and vacuum would be up. Perhaps too much advance?