I had the same problem with the Holley 600cfm I put on my 400M...hesitation just off of idle. I played around with it for quite a while, trying different size squirters, and then accelerator pump cams and what I finally ended up with was a 50cc accelerator pump (its a Holley part #) and a fairly aggressive pump cam (I don't remember which one right now..they come in different colors) and then a larger nozzle. If you only change the nozzle size and nothing else, you could possibly run the accelerator pump dry and then your hessitation comes back-usually when you least need it to happen. Anyway now my 600cfm off idle throttle response is excellent, as good as most fuel injection setups. Hope this helps..a lot depends on your particular motor..mine is a 400M built to about 350HP
Just a side note... although I have had trouble with my truck avenger, some of my friends tell me that the hollies in general can be a lot more finicky. If you want something easy to setup and tune I would go edelbrock route. Holleys see,m to constantly need tuning and tweaking and retuning and things that shouldnt change all the sudden are way off ?!? And to top it off I was adjusting the float levels and the nut got out of whack when I was adjusting it and now it just dumps gas right out the vent holes and I cant get it back to normal. Great, have to send it back to holley just to get the dam float levels reset lol.
09 F-350 V10 4x4 6spd CC/8' ordered 5/26/09 delivered 7/6/09
99 F-150 V6 4x4 5spd RegCab/Short bed
78 Big Bronco 4x4 (a work in progress)
Well finally got a hold of Holley and they are making things right. But get this, they feel that the 670 carb is too small for my motor. That's causing the problems. Ummmm, what? Too big??? Well I don't care anymore, I just want a carburetor. So they are sending me a 770 Street Avenger. I have a sneaking suspicion that they have found an inherent flaw in the Truck Avenger and are going to pull it. Which is why they are switching me to the street avenger. Oh well, I'm not gonna complain because my new 550 hp roller-cam 400M could use the 770 cfm. I'll keep you posted on that one....
CHEVROLET = Cheap Heap, Every Valve Rattles and Oil Leaks Every Time
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