Carb Hesitation
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Senior User
Joined: Aug 2001
Posts: 250
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Carb Hesitation
I have a stock 390 with a 750 Holley. It has had a hesitation when I first push on the throttle. Sometimes it backfires. I figured it was the power valve. But it works fine. It gives a good squirt. I also took it out to look it over and it looks ok.Sometimes it's worse than others. And some times I can give it a couple of pumps and helps. Is it possible to get a larger power valve?
Thanks for your help.
Thanks for your help.
More Turbo
Joined: Jun 2001
Posts: 571
Likes: 1
Carb Hesitation
I also have a holley 750 on mine and it does the same. a buddy said that it is very possible that that 750 is just too big for that engineat low rpm's and that the hesitation is caused by flooding.
just a possiblility
just a possiblility
Post Fiend
Joined: Sep 2000
Posts: 8,238
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From: Oregon
Carb Hesitation
Holleys are all about the set up and come calibrated for general use. This means cars. The center squirter (forgot the technical name) is what gives the carb a dose of gas when you accelerate from idle to keep your rig from bogging down. Just like jets and powervalves, these come in all different sizes (it will be stamped on it, usually 25-30 something). The size of your intake runners, and more importantly, the weight of your vehicle dictate which center squirter is best for you. Heavy vehicles need a longer shot to overcome bog off of idle, this means a smaller center squirter. I have a a 750 Holley on my truck, with the stock squirter it too bogged off of idle. I put in a #25 to lengthen the shot and no more problem. This is a one screw/one minute fix, so give it a try. These center squirters can be bought by themselves or you can pirate one of any old Holley laying around. I think you can find #25s in 600 cfm Holleys. Let us know how this works.
Senior User
Joined: Sep 2000
Posts: 435
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From: Central Oregon
Carb Hesitation
That's interesting, because I have gone all the way to the Reo pump plus MAJOR upsize on the nozzle in my 1850 in an attempt to get a little bog out of mine after switching to an Edel Performer. It's still not quite "there". This makes me wonder if maybe I should work back down with the nozzle size? Anybody else experience this?
Steve
Steve
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Joined: Oct 1999
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From: yes
Carb Hesitation
I've heard to use 35's as a good starting point for drag racing, but every combination is different, you could try getting a kit to tune the accelerator pump system, it has different sized quirters, you can also get different pump cams which can help as well.
Post Fiend
Joined: Sep 2000
Posts: 8,238
Likes: 3
From: Oregon
Carb Hesitation
I don't know about edels, but on a Holley a smaller squirter lengthens the shot which compensates for heavy vehicles. Many guys put in larger squirters thinking it simply needs more shot, but this is the opposite of what it needs...it needs duration. Anybody who runs Holleys should pick up one or two of the build books that are out there for them, it explains the physics of this stuff.
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Senior User
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Carb Hesitation
Thanks for the info. Duration on the shot is exactly what it feels like the truck needs when I give it gas. I'll give that a try.
Thanks again
Thanks again
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Post Fiend
Joined: Sep 2000
Posts: 8,238
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From: Oregon
Carb Hesitation
Good luck. My 750 had (I think) a #35 and I went all the way down to a #25 to cure the problem. Let us know if this works. 
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Thread Starter
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Senior User
Joined: Aug 2001
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Carb Hesitation
Well that seems to have fixed the problem. I got the #25 size which is the smalles one. I've only taken it for a short test drive, but it ran fine with no hesitation.
Thanks again for the info
Rocky
Thanks again for the info
Rocky
Post Fiend
Joined: Sep 2000
Posts: 8,238
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From: Oregon
Carb Hesitation
[updated:LAST EDITED ON 18-Jan-02 AT 10:47 PM (EST)]Great! I'm glad that did it for you. It seems like allot of guys are unaware of that little piece of Holley physics. I just love this board...nothing better than helping out other Ford Freaks 
Senior User
Joined: Sep 2000
Posts: 435
Likes: 1
From: Central Oregon
Carb Hesitation
Proeliator -
Just had to get back to thank you for the clue on the shooter size in my Holley 1850. I finally climbed under the hood today and replaced the #42 shooter with a #28. When I took it for a test-drive, it was back to its old self, not a trace of hesitation. When I think of all the fiddling and noodling that I did
. . . plugs, wires, coil, dizzy cap, fuel filters, compression check, yadda-yadda-yadda.
Yep, bigger isn't always better; seems like I heard that somewhere before. I did leave the Reo pump on, and hope that won't be a problem in the long-run.
This also goes to prove that time-worn adage "only change one thing at a time so you can tell what each thing is doing"!
Anyway, thought you might like to hear a success story from a humbled shade-treer!
Steve
Just had to get back to thank you for the clue on the shooter size in my Holley 1850. I finally climbed under the hood today and replaced the #42 shooter with a #28. When I took it for a test-drive, it was back to its old self, not a trace of hesitation. When I think of all the fiddling and noodling that I did
. . . plugs, wires, coil, dizzy cap, fuel filters, compression check, yadda-yadda-yadda. Yep, bigger isn't always better; seems like I heard that somewhere before. I did leave the Reo pump on, and hope that won't be a problem in the long-run.
This also goes to prove that time-worn adage "only change one thing at a time so you can tell what each thing is doing"!
Anyway, thought you might like to hear a success story from a humbled shade-treer!
Steve
Post Fiend
Joined: Sep 2000
Posts: 8,238
Likes: 3
From: Oregon
Carb Hesitation
Hey, thanks, I appreciate the feedback! I'd appreciate the feebback on my user rating too 
It seems like (for one reason or another) the center squirter is the last thing thought about and many times the only thing really needed to change. Well, now you know this little trick, and when one of your buddies runs into this problem you can come off as an old Holley guru
It seems like (for one reason or another) the center squirter is the last thing thought about and many times the only thing really needed to change. Well, now you know this little trick, and when one of your buddies runs into this problem you can come off as an old Holley guru 
New User
Joined: Apr 2001
Posts: 24
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Carb Hesitation
I also have the EXACT same setup in a 1955 Ford F100. It does the exact same thing when I punch the throttle from a stop or well moving.
I put a trick kit in it and it didn't help. Replaced the jets and power valve with the kit and nothing. I mess with the fuel level constantly and cannot get rid of it. I also tried adjusting the timing both advance and decrease and still does it. I am upgrading to a Demon and an MSD pro billet electronic distributor. I will let you know how I make out.
Good Luck
Travis
I put a trick kit in it and it didn't help. Replaced the jets and power valve with the kit and nothing. I mess with the fuel level constantly and cannot get rid of it. I also tried adjusting the timing both advance and decrease and still does it. I am upgrading to a Demon and an MSD pro billet electronic distributor. I will let you know how I make out.
Good Luck
Travis
Post Fiend
Joined: Sep 2000
Posts: 8,238
Likes: 3
From: Oregon
Carb Hesitation
Both the demon carbs and the msd ignition are top of their game in my book. Which center squirters have you tried in fixing your problem illum? Although, your problem must be elsewhere cuz you said it also happens rolling down the road when you put the hammer down...that sounds more like a bog from too much fuel...but I guess since you are getting a new carb we'll just hope that takes care of the problem. If I wasn't running an off-road carb I'd run a Demon too.
Senior User
Joined: May 2001
Posts: 178
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From: Columbia, TN
Carb Hesitation
Proeliator,
My does the samething I have a 2bb on a 390 and when I give it gas it Hesitates, but if I press the gas pedal real slow it's ok. What is the Part called that I need to replace and where do I get it. Do you any info on how to do it.
Thanks
The Carb is new it was replaced about 2 weeks ago and thats when it started.
My does the samething I have a 2bb on a 390 and when I give it gas it Hesitates, but if I press the gas pedal real slow it's ok. What is the Part called that I need to replace and where do I get it. Do you any info on how to do it.
Thanks
The Carb is new it was replaced about 2 weeks ago and thats when it started.