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Rochester B, BC, BV Carburetor Troubleshooting

When Braking Hard Carburetor Floods

The warpage in the castings allows gasoline which sloshes up above the top of the bowl upon hard braking to get together with an exposed source of manifold vacuum and the engine stalls because it can’t handle a straight shot of unmetered fuel. Complaints of stalling in left-hand turns on cars equipped with Rochester 4-Jet and Carter WCFB: same deal. All the vacuum circuitry runs down the right-hand side of the carbs.

Solution: straighten the castings. This can be done by putting the casting in a vise and heating it up until straight. Last but not least: Add a 2nd float bowl gasket.
Plugs Turn Black When Idling 30 Mins 3 Times In A Week The first thing to check is to see if the choke valve is opening all the way when it gets warm. It is possible that the choke is closed when cold and just sitting there idling, the fast idle may be keeping the choke valve from opening. Look down the carburetor at idle to see if gas is dribbling out of the main discharge. This would indicate the main discharge check ball is leaking. Tap the ball lightly to get it to seat better.

Hesitates or Bogs

So when you press on the throttle, the engine seems to stall, then picks up speed.

This could be the distributor advance not working correctly, or

there is a problem with the accelerator pump circuit.

  • There is a passage that goes from the hole above the idle mixture hole. This is the idle transfer and can cause some hesitation off of idle. Blow the passage out.
  • If the engine has been sitting for months, then the gas may have turned and varnished the inside of the carburetor. Clean gas tank, fuel lines and carburetor. Filling the tank with clean gas will not take care of the problem. The varnish is probably sticking to the inside of the tank walls waiting to get into the carburetor.
  • Accelerator pump cup is damaged, either by ethanol or wear.
  • The main discharge check ball may be installed wrong, or leaking. There should be a check ball, spring, then the T. Test for a leak by adding mineral spirits to the pump well and push the pump down forcing fluid through the main discharge. Hold the check ball down using a drift pump. If you feel pressure and not fluid then it is OK. Otherwise, tap the ball lightly to form a good seat.
  • The intake check ball might be missing. Starting with the pump all the way down, pull it out. The well should fill up with fluid. Some will have a check ball in the bottom of the well. There would be 2 holes in this case. Some will have a intake check ball outside of the well but next to it. There is usually a screen above the check ball. Be sure it is clean and loose.

Updated on 01/03/2021

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