At part throttle your vehicle is surging (rpm is going up down like a yoyo)
Don’t blame the carburetor right away. Especially if you had this problem before rebuilding, or replacing the carburetor.
Chance are it’s the timing, or the vent to the gas tank. Make sure the vent is clear. In some cases there may be a check valve in the vent line.
How Loose Can The Throttle Shaft Be?
Probably around 1/32″ of free play, but more importantly what does it do when you spray carb cleaner around the shaft. If the RPM stays steady, you don’t need to do anything about the shaft.
When you do need to bush the shaft use 22-172 bushings.
Flooding on an Edelbrock carburetor is a situation where the float bowl is getting too much fuel and it is pouring over the top.
Some of the causes, not in any order.
- Fuel pump pressure – test your fuel pump. New pumps are especially suspect. Should be 4 to 5 lbs.
- Bad float – heat some water and immerse your float. Bubbles would indicate a leak.
- Float sticking – gently move the floats up and down to make sure they aren’t sticking somewhere.
- Worn float pin
- Needle – Putting any pressure on the needle when adjusting the float can damage the viton tip and then it will not seal. Test the needle & seat
- The seat uses a metal washer and they don’t always seal. Unscrew the seat and screw it back in will help. Turn the top upside down with the floats resting on the needles. Blow in the inlet gently. You should not be able to blow through.
- Float level – Should look level with the top upside down.
- You may be getting dirt in the needle & seat – this could be caused by a dirty, or old gas tank. Ethanol is a great gas tank cleaner. Unfortunately years of built up material on the inside of the gas tank will be sent up to the carburetor.
Off road – you may need a spring loaded needle & seat.
Hard starting can be from so many different things that it is hard to point to any 1 thing.
You 1st need to determine if the hard starting is from flooding, or lack of gas.
If when you do get the vehicle started and you see black smoke out of the tailpipe, then you are flooding.
If the smoke out of the tailpipe is not black, then you are probably too lean.
Too Rich (too much gas)
- Check the points, plugs, wires and any other ignition component.
- Look down the carburetor after turning it off. Any gas dribbling from the venturi indicates a problem with gas getting siphoned from the float bowl.
- Test the main discharge.
- Gas cap should be vented – test by driving with the gas cap loose and look for discharge problems.
- Vent line going to the gas tank might be plugged.
- Check for any carburetor vent plugging.
- Float level
- Float leaking
- Needle & seat leaking
- Fuel pump pressure too high
- Popping through the carburetor might indicate a lean condition.
- Fuel pump pressure too low.
- Kinked, or collapsed fuel line. Be sure all rubber hose is injector ready. Ethanol can eat the inside of rubber. Any black particles in the float bowl would be an indicator of the Nitrophyl float getting eaten, or the rubber fuel line collapsing inside.
- Float level
- Float drop not enough to allow the needle to pull out of the seat.
- Fuel filter plugged. Look for in-line as well as filter screens in the fuel inlet and possibly connected to the needle & seat.
Make sure the choke valve can open & close. If the valve is stuck closed, then the engine won’t get enough air to start.
Edelbrock Carburetor Kit
- Replaceable accelerator pump cup
- Float bowl gasket
- Mounting gasket
- Air cleaner gasket
- Viton tip needle & seats
- Return spring
- Check weight
- Metering rod retainer springs
- Venturi gaskets
- Choke retainers
- Float valve springs
- Fuel inlet screen