Running a SP 12a with RB headers, exhaust, Holly intake and Carter/Edelbrock, stock ignition. I just rebuilt it and has about 1200 miles on it. It idles smooth at about 900, but after about 1/2 throttle or more when you back off throttle to shift it will sputter and at times when you come on the throttle it will stumble a little. The plugs looked like it was running a little lean. They were white to light brown so I opened up the mixture screws about 1/4 turn and didn't seems to help. It's got about 10-11" of vacuum the way it is set right now which seems to be about max at idle. The carb has been rejetted for a SP rotary and only has about 3K miles on it, but was setting for about 3 years. Is it possible I need to rekit it or any other suggestions.
Thanks,
Todd

 

If it was sitting for that long I would change fuel filter, run some seafoam through the gas tank for a bit and hit the carb with a lot of carb cleaner. If that doesn't help I would check the fuel pressure and make sure its holding up under throttle. Maybe thats the cause of the leaning. After that I would pull thecarb and completely clean and while its off might as well rebuild it, its not that hard if your already got it off and taking things apart to clean it.

 

Car has been running, just rebuilt engine. Everything is new except the carb is what has been setting for 3 yrs. New Red Holly FP, regulator set on 5.5 lbs, fuel lines, filter, ect. Like I said the plugs looked as they were burning lean. White to light brown. I figured a med. brown would be close to right. I suppose throwing a rebuild kit on the carb would be a good place to start/
Thanks,
Todd

 

you can adjust the accelerator pump and try diff springs for the metering rods. What color springs are in there now??

 

Carb needs cleaning, probably clogged jets. First place to start.

 

OK, guys, thanks. I think I will rebuild it this weekend.