new holley carb problems
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Elder User
Joined: Jul 2002
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From: USA
new holley carb problems
just finally got the new holley carb on the truck, hadnt adjusted it to well, and it back fired twice 
, not too bad but still a backfire nonetheless, finally coffed up some cash and got the carb professionally tuned by a shop, he said it was running great, but now it sputters off the line due to something wrong with the acc pump, so i need to know how to adjust that too, but when it idles it idles weird sometimes and is not smooth at all compared to the old stocker....what do i do know???
1977 F250 460
C6 Hedman Headers
Dual 40 series
edelbrock performer
holley 4150
msd 6a and blaster coil
, not too bad but still a backfire nonetheless, finally coffed up some cash and got the carb professionally tuned by a shop, he said it was running great, but now it sputters off the line due to something wrong with the acc pump, so i need to know how to adjust that too, but when it idles it idles weird sometimes and is not smooth at all compared to the old stocker....what do i do know??? 1977 F250 460
C6 Hedman Headers
Dual 40 series
edelbrock performer
holley 4150
msd 6a and blaster coil
Post Fiend
Joined: Apr 2002
Posts: 5,964
Likes: 1
From: Woodruff, SC
new holley carb problems
Seeing that it is a holley when it backfired it might have blown out the power valve.
Just my 2 cents
Wiz
An Equal Opportunity Truck Lover!
http://www.clubfte.com/users/thewiz427/index.html
Just my 2 cents
Wiz
An Equal Opportunity Truck Lover!
http://www.clubfte.com/users/thewiz427/index.html
Thread Starter
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Elder User
Joined: Jul 2002
Posts: 526
Likes: 0
From: USA
new holley carb problems
so i started to pl;ay around with the carb this morning, now i got it to idle smoothly but my hesitation off the line still exists, i know its the accelerator pump, but i dont know what to do about it, i checked and there is a steady stream of fuel going into the carb when i move the throttle by hand, do i need a bigger acc pump jet or sumtuing?
1977 F250 460
C6 Hedman Headers
Dual 40 series
edelbrock performer
holley 4150
msd 6a and blaster coil
1977 F250 460
C6 Hedman Headers
Dual 40 series
edelbrock performer
holley 4150
msd 6a and blaster coil
More Turbo
Joined: Dec 1999
Posts: 582
Likes: 5
From: New Orleans United States
new holley carb problems
It sounds like it is going lean when you hit the throttle.
When looking at where the throttle linkage connects to the carb, look on the backside of the carb's linkage that rotates when you hit the gas, and you will see a little plastic "cam" that moves the lever to drive the accelerator pump. One Screw holds the cam to the linkage, and the cams are color coded for different cc's of fuel per 10 strokes. Also, each cam has two holes that mount it to the linkage numbered 1 and 2. Mounting it in either hole will also alter the amount of fuel dumped in by the pump.
I have the same problem of when and if I absolutley stomp it, it will backfire up through the carb and kill the engine. So this means i need more of a shot earlier in the linkages travel, so I need a cam a with more lift earlier in the travel of the pedal.
Hope this helps explain it a little.
When looking at where the throttle linkage connects to the carb, look on the backside of the carb's linkage that rotates when you hit the gas, and you will see a little plastic "cam" that moves the lever to drive the accelerator pump. One Screw holds the cam to the linkage, and the cams are color coded for different cc's of fuel per 10 strokes. Also, each cam has two holes that mount it to the linkage numbered 1 and 2. Mounting it in either hole will also alter the amount of fuel dumped in by the pump.
I have the same problem of when and if I absolutley stomp it, it will backfire up through the carb and kill the engine. So this means i need more of a shot earlier in the linkages travel, so I need a cam a with more lift earlier in the travel of the pedal.
Hope this helps explain it a little.
Moderator
Joined: Jan 2001
Posts: 56,979
Likes: 2,734
From: Virginia
new holley carb problems
There is a difference between a hesitation when you gradually move the throttle open, vs if you hit or tap the throttle. If you tap or pat the gas, and the truck lurches forward and then bogs or hesitates, this tells me it's not the accelerator pump system, but the transition circuit from idle to when the main circuit kicks in. Do that little test to see which one it is. If it is the accelerator pump, then it will bog right away when you pat the gas.
If it turns out to not be the accelerator pump, then it will be a little harder to fix. Usually a hesitation in the transition circuit is caused by the throttle plates being open too far. I would slow the idle down, and then re-adjust the idle mixture screws to see if the problem goes away. Your timing will also affect this. You can set your timing up a little, which will make it idle faster, and then you can turn the idle adjustment down on the carb and then re-adjust the idle mixture screws.
If it turns out to not be the accelerator pump, then it will be a little harder to fix. Usually a hesitation in the transition circuit is caused by the throttle plates being open too far. I would slow the idle down, and then re-adjust the idle mixture screws to see if the problem goes away. Your timing will also affect this. You can set your timing up a little, which will make it idle faster, and then you can turn the idle adjustment down on the carb and then re-adjust the idle mixture screws.
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Moderator
Joined: Dec 2001
Posts: 22,436
Likes: 17
From: Louisville,Ky.
new holley carb problems
If it hesitates as soon as you go to accelerate, then try a larger squirter. They usually come with a #25. Try a #28, then if it improves but isn't totally gone, then try a #31.
If it starts to accelerate, then bogs then picks back up, you need a longer squirt. I would try a #25 with the tubes sticking out. This will increase the legnth of the squit. Or, you could tighten up the nut on the spring that is on the pump arm. Don't tighten it too much, just one turn at a time.
Another hint, if you can turn in the idle screws and the motor dies, the power valve is ok. All new Holleys come with a check ball to keep them from blowing now.
Make sure that the vac. adv. hose it hooked to the side of the carb. There is a hook up on the pass. side about 1/2 way up in the front metering block. This is the ported vacuum for the distributor. If it is hooked to the bottom front of the carb, then move it and reset your initial timing to about 10 degrees.
If it starts to accelerate, then bogs then picks back up, you need a longer squirt. I would try a #25 with the tubes sticking out. This will increase the legnth of the squit. Or, you could tighten up the nut on the spring that is on the pump arm. Don't tighten it too much, just one turn at a time.
Another hint, if you can turn in the idle screws and the motor dies, the power valve is ok. All new Holleys come with a check ball to keep them from blowing now.
Make sure that the vac. adv. hose it hooked to the side of the carb. There is a hook up on the pass. side about 1/2 way up in the front metering block. This is the ported vacuum for the distributor. If it is hooked to the bottom front of the carb, then move it and reset your initial timing to about 10 degrees.
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