advice on carb adjustments needed
Thread Starter
Racer
Joined: Jul 2004
Posts: 444
Likes: 0
From: Dallas TX
advice on carb adjustments needed
I'm very new to carbs and I need a little advice on the proper way to adjust the float level. The car would stall when coming to a relatively hard stop and the solution was to check the float levels. I have a Holley 800 CFM double pumper carb (model 4780) and it sounded like my front fuel level was too low. I opened the sight plug with the engine off and it looked low, especially since the rear was high enough to spill out. So I opened up the sight plug while the engine was idling and the fuel level was all over the place due to the car shaking. I just put the sight plug back in, turned the car off, and then looked again. I adjusted both front and rear such that they were about at the bottom of the sight hole just after the car is shut off. It fixed the problem of stalling, but I just wanted to make sure I was using the right procedure and didn't mess something up. Is there a better way of checking the level with a lopey cam? Would there be any problems if the level was too high?
Racer
Joined: Feb 2007
Posts: 262
Likes: 2
From: FREDERICKSBURG VA
If your rear float is to high, the fuel spills out of the rear bowl through the vent tube. Your rough idle may be idle mixture not the cam. What engine/cam are you running. Does your 4780 have four idle screws or just the front two? For a base to start from turn the idles screws in til closed, then back out 1.5 turns. Then with car running adjust the idle screws one at a time-slowly-to get highest vacuum or RPM. After each adjustment, readjust your idle stop screw to get your idle set again.
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
You have to check the level while the car is running.
Get some clear site plugs.
First thing is the float level, then adjust the idle/air mixure screws.
Star with the drivers side and screw it in until the carb starts to run rough then back it out until it smooths out, go to the other side, then redo it.
Otherwise rough running and smoke = wrong or busted power valve, chnage front one to a 3.5 and if you have a back one, 2.5.
Get some clear site plugs.
First thing is the float level, then adjust the idle/air mixure screws.
Star with the drivers side and screw it in until the carb starts to run rough then back it out until it smooths out, go to the other side, then redo it.
Otherwise rough running and smoke = wrong or busted power valve, chnage front one to a 3.5 and if you have a back one, 2.5.
