The Stovebolt Site Forums The Shop Area Engine Shop Carb worse after rebuid

After a long debate with myself I finally rebuilt my Monojet carb. Now the truck runs worse than it did before I tackled it. I carfully took it apart and soaked it in solvent. Blasted compressed air through everything. Replaced all the stuff that came in the kit and adjusted the metering rod and float levels according to the instructions. Now the truck has no power, when you step on the throttle it makes a blah, blah, blah sound until the RPM slowly climbs up. No backfires. At idle it sounds fine and you can rev it up in park and it doesn;t have the same problem, but put it in drive and you have to be real gentle on the throttle it get anywhere. I'm really choked!!! BTW all this is with a warm engine and no choke. Before the rebilt it would bog a bit when you hit the throttle hard, but only for a second or 2.
One suggestion was problem was in transition from idle circuit to main run circuit. Going to try and put the metering rod and float back to around where they were before I tried to follow the instructions. Engine is a '70 250.

what about your air fuel mixture screw? 1/4 turn past peek rpm at idle (about 2-1/2 turns)

Did you get the accelerator pump together wrong or plug up one of the passages by accident? Check to make sure it gets a healthy squirt of gas by pumping the accelerator with the engine off while watching down the bore. Also, make sure the power valve is working. It senses a drop in vacuum and richens the mixture for acceleration. If you got the wrong spring on it, it's vacuum passages are plugged (by goop or a misplaced gasket) or it is stuck it will do exactly what you described.

Thanks guys....

Will check the acc. pump...but what the hell is the power valve? Is that the little spring and ball?
The idle mixture is about right... I turned it until the idle stumbled and then backed it off a bit.
I really don;t like (understand) carbs!!

I recommend that you get a book on Rochester carbs, there are several out there. I will have to look at the exploded diagram of that carb when I get home to find the powervalve. They are slightly differant in each case. It generally consists of a small springloaded piston connected to either a valve or a metering jet. It bypasses the main jet.

I decided I should look at the exploded view of the carb and found the power jet. Re-ajusted the float and it's a bit better. I think I over adjusted the metering rod and it's not letting enough fuel through. When I choke it a bit the motor runs better. Had a chance to talk to a real mechanic and he agreed it sounded like ti was running too lean.
I will get at that change a bit later. With a carpenter coming over tomorrow getting the wood for a new deck takes priority.
Thanks for the help.