Holley Carb Question on Pump Lever Adj & Idle Adj

[TX-ZACH]

Doing maint checking my plugs I was running rich on plug read (all plugs). I was about 1.25 out on fuel/air mix and adjusted to 1.0 turns out to lean a bit. While I was there adj the idle I noticed loosening the idle would not drop. It appears the pump lever adj will not allow to drop. Is there any correlation there? By adj the pump lever out will allow more room to adj idle down? Trying to determine if carb adj or linkage adj is needed. I need to drop idle about 200rpm.

 

[DirtDonk]

Back to the top.
For rich looking plugs, the idle/air mixture screws are not the problem, or the solution. While they may affect it some slight amount, they are ONLY changing the mixture at idle and just slightly (and I mean slightly) above idle.
Everywhere else you have to change other things, such as main jet size and perhaps power valve value, etc.

Speaking of which... Did you check vacuum readings and compare that to what power valve was installed? Assuming this carburetor was just as received and installed out of the box without modifying it in any way? And what exact model and part number carburetor is it?

Sorry can't help on the idle speed vs arm interference, but with the right carb info, someone here will know. Lots of Holley expertise hereabouts.
One thing I can add though, is make sure that when you're setting this stuff that the choke plate is all the way open and all the linkage related to it is returned to it's stock, upright position!
Just to be sure that the choke is not interfering with your messing about with adjustments.

Paul

 

[TX-ZACH]

No vacuum leak detected. Further troubleshooting noticed the fast idle on the choke not kicking off. I could drop the cam and arm manually with finger and at that point curb idle responded with adj. Checked for power at electronic choke connections and no 12v. Found bad connection and repaired. Today I will fire her up again to verify working after warm up.

 

[bmc69]

The accel pump lever will not interfere with the throttle plate closing. The fast idle cam (red plastic piece with a small weight ball in one end) sure will though, because it is supposed to do that until the choke coil is warmed up. Sounds like you found that.

 

[B RON CO]

Hi, I get good results adjusting the idle mixture screws and the idle speed screw by slowly turning a mixture screw in until the engine stumbles, and then out one full turn. Then do the other one, then adjust the idle speed to where you want it. I usually perform this adjustment twice. The engine should be fully warmed up. The ignition tuneup and ignition timing must be set first. I had a feeling Paul was on the right track when he said to check the choke. Good luck

 

[TX-ZACH]

The accel pump lever will not interfere with the throttle plate closing. The fast idle cam (red plastic piece with a small weight ball in one end) sure will though, because it is supposed to do that until the choke coil is warmed up. Sounds like you found that.

If for some reason the fast idle does not kick off after warm, what is next step? Remove choke assy and look for linkage issue or heat sensor?

 

[TX-ZACH]

Back to the top.
For rich looking plugs, the idle/air mixture screws are not the problem, or the solution. While they may affect it some slight amount, they are ONLY changing the mixture at idle and just slightly (and I mean slightly) above idle.
Everywhere else you have to change other things, such as main jet size and perhaps power valve value, etc.

Speaking of which... Did you check vacuum readings and compare that to what power valve was installed? Assuming this carburetor was just as received and installed out of the box without modifying it in any way? And what exact model and part number carburetor is it?

Sorry can't help on the idle speed vs arm interference, but with the right carb info, someone here will know. Lots of Holley expertise hereabouts.
One thing I can add though, is make sure that when you're setting this stuff that the choke plate is all the way open and all the linkage related to it is returned to it's stock, upright position!
Just to be sure that the choke is not interfering with your messing about with adjustments.

Paul

DD

I fattened it up after changing plugs the last time because I was running a hotter plug and paranoid. I had to order a new vac gauge so I'll dial that air/fuel mix today. I am not sure what jets are in there now but has performed well. I switched to a cooler plug Autolight 3924 and adj timing a couple of degrees. I'll do a couple of plug reads and adj if needed.

 

[bmc69]

If for some reason the fast idle does not kick off after warm, what is next step? Remove choke assy and look for linkage issue or heat sensor?

Is the choke element electric heated only?..or heated only from heat pipe connection...or the hybrid combination of both? Need to determine if choke is being adequately heated. If it appears that it is, then simply loosen the screws on the choke housing and rotate it slightly to decrease the choke spring pressure on the choke linkage, allowing the choke plate to open farther/sooner.

 

[DirtDonk]

Also clean and lube the choke mechanism.
By that I mean just a few spritzes of carb cleaner, followed by a few spritzes of some extremely light lubricant.
You can leave it dry, and that’s usually the recommendation. However, I found that as some carburetors age, that low friction mating of the plastic and metal parts does not always stay smooth.
And because back then, I didn’t mind an occasional bit of maintenance, I would clean them, then lube them with WD-40, then, when it would start sticking again a few months down the road, just do it again.
This was on my daily driver.

 

[B RON CO]

Hi, once you get the choke to work properly you might be all done after a carb adjustment. If you bought the carb new, the jets are probably very close to being correct right out of the box on a Holley, Edelbrocks are usually too rich. Any reason for going with hotter and cooler plugs? The factory plugs usually work best. Good luck

 

[TX-ZACH]

Warm up today with confirmed 12v to choke and it did the opposite. No choke fast idle engaged at cold and did a 15min cruise come back and fast idle is engaged. Doing the opposite of what is needed.

DD: Back to the plugs. I have Edlebrock RPM Performer Heads and tech sheet states it wants Champion RC12YC. I put those in and ran them a yr after truck came back from motor build with wrong plugs in. Further research an Autolite 3924 may be a safer plug so wanted ti try it. I did a couple of plug reads yesterday after test ride and still rich.

Bronco seems to be running great but not optimized according to plug read. On top of that my new vac gauge either does not work properly or my vacuum sucks. Back to square one. Gonna start by cleaning all linkages and hit with some Rem Oil.

 

[DirtDonk]

What does the vacuum read? What exact camshaft was put in the engine?
Over 20 inches is great vacuum and what you would expect with a stock engine.
A 17 to 20 reading for a very, very mild cam.
Anything even slightly bigger than mild, though, and you’re easily looking at 15 inches or less.

And are you sure you had it connected to the full vacuum port, as opposed to the ported port, where you have to open the carburetor throttle a little to get a vacuum?

 

[B RON CO]

Hi, it is possible that the spring in the choke thermostat is not properly installed onto the choke lever. I would study a video from the carb manufacturer ( you still didn't say what carb you have ) and take the black cover off and reinstall it according to the manufacturers instructions. Good luck

 

[TX-ZACH]

What does the vacuum read? What exact camshaft was put in the engine?
Over 20 inches is great vacuum and what you would expect with a stock engine.
A 17 to 20 reading for a very, very mild cam.
Anything even slightly bigger than mild, though, and you’re easily looking at 15 inches or less.

And are you sure you had it connected to the full vacuum port, as opposed to the ported port, where you have to open the carburetor throttle a little to get a vacuum?

Ok I feel better now. I struggle to get 14-15# on intake vac. Ported its at 0 until throttle is opened.

My best guess are these cam specs as follows. The motor was done 2021 when Ford 302-351 blocks were unicorns to find. My builder sourced an ATK mid dress crate motor w/ 365HP. I upgraded the heads to Edlebrock rpm performers and shorty headers. I kept the Holley 600cfm from the existing 302 that was in it. Its either a 4160 or Street Warrior. Not sure if you remember but I'm the guy that found this place after bringing the Bronco home from purchase and motor eat itself coming off a trailer from airbreather all-thread fastener found its way on top of a piston.

from ATK website

• Pistons: Hypereutectic 9:1 compression
• Rings: Moly
• Camshaft: Hyd. Roller
• Cam Specs: 220/224 @50 .512in/.512 ex 112LSA

 

[DirtDonk]

I do remember. And with those cam specs, I’m not surprised at the vacuum reading.
So I think that’s normal.
There are others here that have used a lot more different cams that I have though, so maybe they will weigh in with your expected vacuum readings.
You could always try to advance the ignition timing as well to see if the readings go up slightly.
Obviously you can only adjust the timing so much, based on other parameters, but if you can get more advance you might gain a pound or two.

 

[TX-ZACH]

Thanks for checking in here, yes 15 is all I ever got out of it over the past couple years.. Although I have had vac leaks in the past I am fairly confident I have them all tight and right. I adv the timing a couple degrees to help with fouling plugs. It seems to be happy where I have it (18*).

 

[Broncobowsher]

Probably worth investing in a wide band A/F meter.
I would not bother trying to read plugs until the choke is working right.
15 minutes driving around the neighborhood at near idle is a lot different than driving 15 miles at highway speeds. I don't give a 15 minute drive much creed for getting the plugs cleaned after a rich start up unless they have been run hard enough to really get warmed up and cooked off. They will look rich just because they have not been run hard enough to clean themselves after the start. Sounds like you are trying to heat the plugs up by advancing the timing.

 

[TX-ZACH]

That definitely would help. I just bumped a couple of degrees to test if it would run better with new plug set up or make a deference. My issue is with the carb.