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Old July 28th, 2014, 09:41 PM   #1
jeepbob
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Talking holley carb hesitation FIXED

I have a very annoying hesitation between idle and wot. I am running a 600 cfm holley with vac secondaries in a CJ5 on a 302 Ford. the engine has a mild cam (almost stock). the problem occurs problem only occurs under very rapid stomping of the throttle. the accelerator pump has been changed and adjusted. I have changed acc pump squirters and it got better. the secondary spring seems very light. I am under geared (3:54 w/33" t/a's) but it accelerates very fast once the hesitation is gone. If I accelerate moderatily to about 2500 then stomp on it, there is no hesitation. I am thinking that the secondary spring is to light and they are opening too fast. Power valve is a 6.5. Any ideas, am I close in my thinking or can you guys come up with another ideas

I found the problem. The secondary spring was too heavy and the secondaries were not opening until about 2700rpm. This was where the secondaries were opening. I bought a spring set and followed thier recommmations and went with about half way with the spring rate. The stumble went away and had slight bog went one more spring lighter and now runs great!

Last edited by jeepbob; August 31st, 2014 at 03:07 PM. Reason: problem solved
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Old August 3rd, 2014, 12:34 PM   #2
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I too have had similar issues, only mine on a 390 with a 650cfm. My original problem was similar, if I stabbed the throttle under 1500rpm it would hesitate or sometimes even backfire ( if there was too much load on it). I tried rebuilding the carb to no avail but I'm no carb expert. That problem has since turned into a consistent stumble somewhere in the rpm range, adjusting my timing will move the stumble to different rpm locations but won't make it go away.

I'm currently thinking I'm under jetted, have distributor problems or maybe a cam issue. I have a small collection of holley 650's and I'm going to swap back and forth to try and rule out a carb issue. I don't know if this helps, let us know what you find out.
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Old August 3rd, 2014, 03:04 PM   #3
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First.....make sure float levels are correct....should be at the bottom of the sight plug..so it almost trickles out with the engine running.

Make sure the lash for the pump arm is correct, I like a very minor amount of play...almost zero lash....any past zero lash and you are losing pump travel.

What squirters are in it now?

You can disconnect the vac. secondarys, wire it so it can't open and drive it....if the hesitation is gone maybe look at a different spring.
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Old August 5th, 2014, 03:54 PM   #4
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Default holley carb hesitation

I had the same issue with my Holly 600. Took it to a old school shop, where they adjusted float level, they were too high and adjusted fuel/air level, I was running too lean. No more hesitation, backfire and I noticed my engine runs a bit cooler
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Old August 31st, 2014, 05:12 PM   #5
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