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Discussion Starter · #1 ·
I have a couple of 450 holleys on my engine and the accelerator pump will not squirt on the primary carb unless I open the throttle up almost half way. I tried to adjust the linkage on the pump, but that didn't help. The carb was rebuilt, so the acc pump is fairly new. The thing creates a dead spot. Any suggestions
 

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The Smell of Nitro in the morn
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The Knowlegde Base has the info & sites that you need. :thumbup:
 

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Discussion Starter · #4 ·
onovakind67 said:
What color pump cams do you have in them and what position are they in?
That's most likely part of the problem, I'm not sure what your talking about. If your talking about the pump arm, it's black, position,??????
 

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Race it, Don't rice it!
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Attached to the throttle linkage near the throttle shaft is a plastic pump cam that the pump arm rides on. So when you open the throttle the cam turns and pushes on the pump arm lever. Holley has eight different pump cams to tailor to individual needs. They are distinguished by color. There are two screw holes in the pump cam. The screw can be reached easily. It's just one screw. These are the "positions". Try playing with moving the pump cam in the other positions and see what happens. You are trying to get the pump action to occur right off the idle position. leave a few thousandths of space under the arm adjustment so the pump doesn't trickle fuel under vibration.
 

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These are the various pump cams. You can install them in one of two positions by using the appropriately numbered hole on the cam. For each 10 strokes of the pump they will provide the following amount of fuel:

cam color #1 #2

white 17cc - 19.5cc

blue 18cc - 20cc

red 18.5cc - 20cc

orange 19cc - 24.5cc

black 19cc - 18cc

green 24cc - 30cc

pink 30cc - 37.5cc

brown 36cc
 

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Twin Turbo Drag Boat
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Does the cam push the accel pump arm immediately? the clearance is set correctly?

If so just make sure the diaphram is still good, no passages are blocked by gasket and the check valve is not sticking.
 

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Discussion Starter · #8 ·
It has a white cam, and the pump arm does move when throttle is pushed. Would a low fuel level cause the problem, because the motor sit's up on a higher than normal angle. I had to lower the primary float level to keep the fuel from filling the secondary bowl VIA the bowl tube because of the angle.
 
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