holley idle issues

-
P

prodart340

Well-Known Member
Joined
Oct 27, 2007
Messages
668
Reaction score
2
Location
middleway,wv
the 750 dbl pumper on the 340 is giving me a fit:banghead:, after it gets warmed up the idle goes up to about 1200 rpm. I replaced the vacuum plugs, checked to make sure the distributor was tight and the cap while I was there but still no worky!!!!!!!!!!! any suggestions from all the carb guys on where to start from here? thanks in advance ,mike
 
Check your baseplate for warpage or if it's an older carb, the throttle shafts wear the bore and it starts sucking air through the gap. Got a lot of play in the throttle shafts?
 
68383GTS said:
Mine was doing this and the return spring was just a little to weak. Jim
Click to expand...

I remember a friend having this problem, dont know if he got it fixed or not, he was having trouble figuring it out. why would the primaries open up a little just because the engine temp got warmer, wouldn't it do it when cold too if were just a spring?
 
Hey fella, good to meet you and your wife @ cruise in today. Linkage hanging up? Snug base nuts up? Blow any sealant out under intake manifold? Hope you find your gremlin.8)
 
No mine was OK cold.But when it warmed up the idle was to high.I would readjust the idle and it would be OK.Take it for a drive and the idle would be to high.The throttle looked like it was all the way back,but I took my finger and pushed it back just a hair and it would idle down.So I put a stronger spring and it was OK.If this sounds like what its doing you may try and push the throttle back once its at idle and see what happens.
Jim
 
Also do you have Holleys Mopar throttle cable adapter on it.The adapter does not come with the carb you have to buy it seperate..

Jim
 
thanks guys,I'll know more in the morning when I get a chance to hit the garage,,,,,,,,nice to meet you too mopar head, stop on in sometime, you can check out the litttle ladies charger project
 
I have owned and played with Holleys for almost 40 years; will never install an other one on my cars. POS
The Quadajet on my boat is a better carb.
 
thanson_mopar said:
is that a common holley problem? I have heard of trouble with throttle shafts before on holleys.
Click to expand...

Mostly on older carbs where someone cranks down the baseplate too hard. It warps the base and the throttle shaft bores start to wear really fast. They can be rebushed or you can just replace the base with one these really nice billet units from QuickFuel. They have a secondary idle adjustment on the top for easy tuning, come with three linkages (super progressive, progressive and 1:1), are much stronger, etc.

hex0.jpg
 
ramcharger said:
Mostly on older carbs where someone cranks down the baseplate too hard. It warps the base and the throttle shaft bores start to wear really fast. They can be rebushed or you can just replace the base with one these really nice billet units from QuickFuel. They have a secondary idle adjustment on the top for easy tuning, come with three linkages (super progressive, progressive and 1:1), are much stronger, etc.
Click to expand...

I see, thanks for the info, my holley dp is an older model. I didnt know quickfuel made bases for them. When the throttle shaft gets too worn it just makes a vaccum leak right?
 
thanson_mopar said:
I see, thanks for the info, my holley dp is an older model. I didnt know quickfuel made bases for them. When the throttle shaft gets too worn it just makes a vaccum leak right?
Click to expand...

Yep. You can test by squirting some WD-40 on the shafts. You'll hear the engine pick up speed or drop revs depending on the present idle fuel mixture settings. A straight edge will show the whether the throttle body is warped or not.
 
ramcharger said:
Yep. You can test by squirting some WD-40 on the shafts. You'll hear the engine pick up speed or drop revs depending on the present idle fuel mixture settings. A straight edge will show the whether the throttle body is warped or not.
Click to expand...

Thanks, Ill keep that in mind and give it a try sometime i go home, every once in a while my carb acts up with idle. Going to buy a book on holley carbs, id like to learn more about them. They didnt teach us about aftermarket carbs or performance tuning with them in autotech haha
 
throttle shaft bushings were worn out,trip to the local speed shop checked to confirm. one phone call found me a quick fuel 750 with 14 passes on it for $250 \\:D/
 
If it only does it when the motor is hot then it more than likely is a vapor lock situtation. I just went through the same thing but it was the way I had my line ran that was causing a problem. Make sure you have good fuel pressure at all times hot or cold. The carb will go lean if there is vapor in the lines and it will idle up on you.... mine did. I couldn't figure out what it was until the motor started shuting down in stop and go traffic. Then that's when I started to look real hard on what the problem was. It started out that the carb would not idle down even though the throttle lever was pulled all the way closed. I also wrapped my lines with heat proctection from DEI.
 
thanks ramcharger, I just got done installing it and got the floats set, but I'm not sure of how to adjust the four screw idle mixture screws,,,any help with that??????????? :yawinkle:
 
prodart340 said:
thanks ramcharger, I just got done installing it and got the floats set, but I'm not sure of how to adjust the four screw idle mixture screws,,,any help with that??????????? :yawinkle:
Click to expand...

air fuel should be able to be adjusted by puting a vacuum gauge on one of the ports that has constant vacuum on the carb, then screw air fuel screws in all the way then back them out a turn and a half. Keep unscrewing them until you have maximum vacuum, if vacuum starts dropping then your too far.
 
First make sure that your timing is set where you want, then set all 4 screws to 1 1/2 turns out from bottom then start and warm the car up. Once it's fully warm, set your speed and connect a vacuum gauge to a full manifold vacuum port.

Now, bring your screws in 1/8 a turn at a time and see if vacuum drops or rises, if it drops, bring them back out 1/8 turn at a time. Keep in mind you may have to make idle speed adjustments while you do this.

Thanson was right on. The key is to get the most vacuum possible @ idle. Sometimes one screw may need to be a bit richer or leaner than the next, but they should be pretty close. If there's more than a 1/4 turn variance, something else is wrong. : Good luck.
 
I have a HP carb with 4 idle screws and found that all of them turned out 3/4 is all I needed. It seems like I didn't have to turn them out as far as a carb with just 2 idle screws. I guess the addition of the 2 idle screws makes up for it therefore you don't have to turn them out that far.
 
I had a similar problem that drove me nuts for over a year. Turns out there was a little notch worn in the throttle cable that would just hold the throttle open enough to cause the engine to idle at 1000-1200 rpm. Would happen when cold and wouldn't happen when I was out there fiddling with it.

When I noticed the worn area in the throttle I was able to temporarily fix it by putting more slack in the cable adjustment until I got a new cable.

My not be your issue but certainly worth checking.
 
You must log in or register to reply here.
-

Back
Top