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post #1 of 3 (permalink) Old Sep 7th, 03, 01:11 PM Thread Starter
Join Date: Aug 2003
Posts: 14

i have a holley 600 vaccum secondary carb that i can't seem to get the accelerator pump adjusted right with no lash at idle. I think i'm adjusting it right with two 3/8 wrenches one to hold and one to turn counterclockwise. I tried this but it won't get tight. I have a bog off idle and high rpms. I don't htink it's running too rich. When i first crank it up it sounds like it is idled too low but the more i drive the idle speed is good. there's no smoke out of the tailpipes. Could i put on my choke and drive and if the bog goes away it is probally too lean?I need help because it is driving me crazy
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post #2 of 3 (permalink) Old Sep 8th, 03, 01:09 AM
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If I read your post correctly, it reads the pump linkage is loose at idle. This is not good, it should have no looseness, and should move, squirt fuel, with the slightest movement of the throttle plates.

Usually the pump cam, the plastic piece the linkage rubs on the throttle lever, is screwed to Pos 1 and the top hole of the cam itself.

You may have to remove the pump linkage and bend it to fit.

The proper method to adjust the pump linkage is to have an assist hold the pedal to the floor, then adjust for .015" clearance between the pump lever and the diaphargm arm at max stroke. The pump lever is the actuator for the diaphargm in the bowl. Push down on this with your finger, and adjust the clearance between the spring-loaded screw and this same short arm to .014-.017 inch.

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post #3 of 3 (permalink) Old Sep 8th, 03, 03:57 PM
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Join Date: Mar 2002
Location: Austin, TX, USA
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What color of pump cam are you running and what hole is it in? I fought with accellerator pump issues last year and learned a couple of important lessons.

For one, the lash adjustment is to be done at WOT. Basically, make sure that the pump lever can stroke enough to give you an additional 0.015" clearance before the actuator spring begins to compress. This just ensures you don't bottom out the pump diaphram at WOT. I mistakenly thought I needed 0.015" gap at closed throttle. Stick your feeler guage in, open the throttle by hand and carefully watch the adjustment nut to see if it begins to compress the spring. Adjust it so the spring doesn't compress. Using the pedal to open the throttle often won't give you a good WOT since the pedal usually won't open the throttle the last coulple of degrees.

The other thing I learned is that those pump cams can mislead you. A "big" pump cam doesn't necessarily give you the best shot off idle. I stepped all the way up to the brown cam and did a few measurements with a dial guage. What I learned was that off idle the brown cam didn't give me much of a shot at all. In fact, in hole #2 it reverse stroked until the throttle blades were open a degree or two. Definately for a hot rod that idles at 1500 RPM and hole shots at 5500 RPM - not a daily driver that idles at 800RPM. I found the white and the orange cams in hole #1 gave the best off idle shot for my street machine. Its natrual to assume a bog needs a bigger more agressive accelerator pump cam, but it will often work against you. The problem you describe sounds like too agressive of pump cam in the #2 hole.

If you manage to get the WOT setting correct and the arm flops at closed throttle, the cam is most likely the problem. Bending the arm as Everett suggests is also standard procedure. But I'd start with a white or orange cam first and go from there.


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