OK, Ive had this problem for a little while and now Im trying to fix it. Everytime I start off from a dead stop, or when Im running about 20-25 miles on hour, I get a slight hesitation. My timing is set right now at 10 degrees. I have set it as high as 16 degrees and really didnt see any difference, anything higher than that and it doesnt want to start..........
I just changed out the power valve in the carb with another 6.5 that was in it when I bought the carb new....same result. I also changed out the accelerator pump and that didnt change anything either. I adjusted the accellerator pump, (tightened down the spring some so it sprays gas a little faster) and that didnt help. I adjusted the air/fuel mixture on the carb using a vacuum guage and the best I can get is around 10-11 pounds, which I have an oversized cam installed as well. By the way, it is a 360 automatic with a 600 box automatic choke carb, edelbrock open bore intake. I also adjusted the vacuum advance on the dizzy from where it was when I installed it. It say every complete turn is 2 degrees advance, but Ive turned it 4 times and it seems to help but I know thats not what the problem is......it was doing this before I installed the dizzy! I feel it a carb problem but I dont know what else to try. It just seems that there is a "dead spot" whenever I am crusing around, like everytime I am barely giving it the gas.....like when I push down on the pedal maybe 1/2 to an inch, if that makes sense. Anyone know what I should be looking for or what the problem may be????

 

BTW, concerning the accellerator pump......is it supposed to spray fuel as soon as the throttle starts moving? Ive noticed that when pulling back on the throttle very slowly that it doesnt spray fuel right away. Whats the proper adjustment? I know if I tighten it down too far it will puncture the pump at wide open throttle right?

 

That's the suspect, I believe.

It needs to shoot fuel the moment you put any motion to the pedal..........or it will allow the throttle blades to open and not have any fuel available(instanteously). Giving you a dead spot.

I've always hated the "proper way" to adjust them like Holley mentions.

With motor off, throttle closed, you should just have "wiggle" to the linkage so that it's not actually pushing on the arm. Slip a .020 feeler gage inbetween arm and linkage to make sure. I go by feel. Now also make sure that the spring on the arm is not bottomed out when at WOT. Sometimes the accel arm gets bent up(you say it's new?) and that throws the adjustment too far out of whack to adjust it in.

If you have gap and plenty of spring left at WOT, it should be good.
I've got three vehicles with dual Holleys and no problems.

 

that definitely sounds like it to me too. I actually ended up getting a little bit larger pump jet and adjusted my accelerator pump and my hesitation came to an end. My problem was too little gas and delayed pump shot. If that helps any

 

i always use a piece of paper , if it rips to much just barely slides out ok .

 

W-W, The problem you are experincing is known as "Reversion". It is caused by the overlap on your camshaft on the intake cycle, the valve is staying open as the piston is comming back up. What may help would be to replace the intake manifold with a "Dual Plane" style which will increase the air veloicity and over come the reversion tendency. Do you have a balance pipe between the head pipes? Or a "X" pipe. If not that may work without changing the manifold. Either way you should have one. Headers would also help if you do not have them. Good Luck ,Kenny Nunez

 

I've got headers. The intake was on the truck when I bought it years ago. It had a Holley on it then too, but it had a manual choke so I replaced it with an electric choke. The truck dud not hesitate back then. I'm thinking it may be the pump as well. I adjusted the spring on it but I didn't want to go too far an mess up the pump on WOD.....which I hardly ever do anyway, lol.
One more question. I am going to be purchasing a 2" Carb spacer so I can get clearance for my air cleaner because I installed an hei dizzy. Since my intake is open bore, should I get an open bore spacer it buy a 4 hole spacer? Should i get an aluminum one or one of the plastic ones?

 

I would get a 4 hole, only as that wil help with metering signal to the carb. An open spacer might tend to make it real lazy down low. A single plane manifold isn't the best to begin for low rpm driving and may be the issue you are seeing with the hesitation. Might take a bit more fuel to cover up the big plenum. Pick your poison on what kind(I would get something that is better for heat control, ie: phenolic not alum).

How about just getting a air cleaner spacer to raise just the base plate? I ran one on my '67 as the base wouldn't fit over my 750 Holley very well so I got a 1" spacer under the base to raise the whole thing up. Much cheaper then carb spacer!

 

I tried a 2 inch spacer for my air cleaner but it interfered with my choke by not letting it close when i was trying to cold start it. The one I got is plastic so I might just modify the spacer buy cutting it where the choke lever will operate the choke properly.

 

if you get plastic don't buy the ebay ones , they are P.O.S. i had one on mine caused a vacuum leak no matter what i did , i ended up with a 1" aluminum one .

 

i have a 1 inch aluminum one too, never had a single problem with it.

 

The more I think about it I may just modify the air cleaner spacer I have so the choke plate will work properly. I really dont want to use a carb spacer unless I have too...........
I just hope this weekend I can get the accellerater pump problem worked out, "if" thats the cause of my problem!

 

Aw yes flat spots not good on a woman or an engine..
Holley's are good and mostly trouble free out of the box on stock motors.99% of time. But once you start changing stuff you have to learn to fine tune them to your motor. Back yrs ago it was known if you add headers, cam, hotter ign coil you had to go about 3 sizes lager in main jets. Holley has tried to over come that by making available carb tuning tools. 1. larger pump shooters, 50cc pumps, and 8 pump cams sizes all color coded. The cams can give you a faster pump shot at part throttle or a slower for over all full throttle. Pump shooters 0.25 to 0.31 are the most common. All these work great if you have the acc pump spring setup correctly. This is an area where many people get screwed up and it ends up being the cause of the flat spot. Book says like 0.15 gap when pump lever arm is set at w/o throttle. this is like a 4 hands thing to setup. But when you get this done you end up with a slow pump shot due to the having to much spring clearance= a flat spot. I've at times had to add one 0.25 little washer to make the spring touch on the acc pump spring lever tighter. It just seems like it was hard to get a happy medium until doing this little spacer shim trick. You may have to do this or try it. It is the cheapest try to fix it.. my 2cents bag of tricks
orich

 

i heard that, haha

 

^^^this is the Holley mumbo jumbo that I NEVER follow when setting up an accel pump. Make sure it has air gap when throttle is closed. Make sure it's not bottomed out when WOT. Leave their adjustment procedure in the circular file.