Q & A

Date Codes
Exploded View
Part Numbers
Q & A
Vacuum Secondary Spring Chart

Q & A Most Common Problems:





QUESTION Flooding or have fuel dripping on the throttle plates after engine shut down.

ANSWER Remove the needle and seat from the top of the bowl and take compressed air and blow out all specs of dust/dirt. One spec will stop the needle/seat from stopping the fuel from leaking. Did you also remember to add a gasket and the small piece of steel with a point at one end under the squirter?


QUESTION I have a wet spot of fuel overnight on the bottom of your throttle plates.

ANSWER This is an actual problem I had and was stumped for a while. I removed the fuel bowl and metering block and noticed that the power valve was loose. Place the block in a vise with wood on each side of the vise jaws and tighten to the following specs.



for power valve with multiple drilled fuel opening, torque to 40-50 inch pounds.


for power valve with 2 rectangular fuel openings, torque to 100 inch pounds.


But this is usually caused by percolation. This is when the engine is shut off and the engine temperature rises it causes the fuel to boil in the bowl and leak out of the boosters. There are a couple of things you can do to cure this one is make sure the fuel level is not too high. You can also lower the fuel level about 1/8" below the sight plug hole and this will cure it sometimes. The heat from the engine will rise into the carburetor sometimes and will cause the fuel to boil. Installing a phenolic heat spacer between the carburetor and the intake or a heat shield can cure this. These parts will prevent heat from getting to the carburetor and boiling the fuel.


QUESTION Turning mixture screws clockwise does not lower RPM or stall engine.

ANSWER A carb rebuild is required.


QUESTION Car stumbles for 1/2-1 sec when I cruise and hit the accelerator short or full shot.

ANSWER See step 1a in Setup link on the left.


QUESTION Car bogs when I tromp it.

ANSWER Your secondaries are opening too fast. Go with a stiffer secondary vacuum spring. Or  your running with the incorrect squirter and or accelerator cam for your engine.


QUESTION My vehicle has a stumble from a dead stop. What can I do to cure this?

ANSWER The most common cause of a stumble is not having an adequate accelerator pump shot. The first thing to do is to look at the discharge nozzle and make sure you are getting a good strong pump shot. If not then you need to inspect the pump diaphram for a hole or tear. You will also need to make sure that the pump passage is clear from any trash or debris. First you will need to check the adjustment on the pump. To do this you will open the throttle all the way (WOT). Push the pump arm lever down and then adjust the pump override spring to obtain .015" clearance between the pump arm and lever. If you are having a stumble and no black smoke out the tailpipe then you will need to increase the shooter size. If it stumbles and you are getting black smoke from the tailpipe then it will be nessasary to decrease the shooter size.


QUESTION I can rev the engine when it is in park and the secondaries will not open. Why is this?

ANSWER The secondaries will not open by free revving the engine. The engine needs to be under a load before they will open. If you are still uncertain if they are opening or not you can take a normal paperclip and clip it onto the secondary diaphram rod. You will then push it up against the bottom of the secondary diaphram housing, now you will need to go out and drive the vehicle. When you return you will be able to look at the position of the paperclip on the rod. If it is lower on the rod then you can tell the secondaries opened and how far they opened. This is useful in determining if you need a heavier or lighter secondary spring.




F.Y.I The 1970 manual for a 396/375 or 454/450 front jets should be 70. Rear should be 76.