Quick fuel carb wont tune....

[DonFitzwater]

Happily enjoying an ice cream cone on a hot Fairbanks day and then I'm ready to kill my truck. What gives!?!?!?

Problem is the carb doesn't respond to idle mixture screws on the primaries. I've got a a vacuum gauge on it and the rear mixture responds on both sides nicely. The primaries however do not. They must remain closed or the engine runs rich and stalls. Any secrets to holley type carbs and fuel leaking internally?

Ive verified the secondaries are set properly and the power valve is good. Fuel pressure is 4.5-5 psi. Compression is 150 x 8 and ignition system is set up properly and working as it should.

 

[TFucili]

Sometimes if the float is a little high it will drip fuel through the emulsion tube into the venturi. I know people love them, but I found Holleys to need constant tinkering.

 

[DonFitzwater]

I’ve adjusted float height from the bottom of the sight glass to the top and no change in behavior. Also, it’s so pronounced that I have the choke adjusted to mostly open when cold otherwise this thing will flood quite easily. This is a Quick Fuel carb (HOLLEY with more tuning capabilities) and it has idle air bleeds, 4 corner idle mixture.

There isn’t any fuel dribbling from the squirters or the annular nozzles. I’m stumped. Going to pull it off again shortly and do a total disassembly.

 

[TFucili]

Been a long time since I fooled with a Holley. What about the gasket behind the metering block?

 

[fest3er]

If you don't see excessive fuel running into the primaries, I'd suspect the secondaries aren't closing.

 

[Wayne M.]

Wrong gaskets? I’ve seen Holley carbs misbehave when the wrong gaskets are used. Mainly the body to throttle plate and the metering plate gaskets. Gotta match up all the holes very carefully.
I’ve had excellent luck with Holleys, My preference.

 

[DonFitzwater]

If you don't see excessive fuel running into the primaries, I'd suspect the secondaries aren't closing.

This was my initial thought as well. I’ve had the carb off once and they appeared to be closing. I will be checking again.

 

[DonFitzwater]

Wrong gaskets? I’ve seen Holley carbs misbehave when the wrong gaskets are used. Mainly the body to throttle plate and the metering plate gaskets. Gotta match up all the holes very carefully.
I’ve had excellent luck with Holleys, My preference.

I’ve had really good luck with Holley as well.........till this butt kicker.

 

[jhenderson]

Big cam? If the primary throttle plates are open too much to get idle speed it’ll uncover the idle passages and render the idle adjustments ineffective. The solution for that is to bump the throttle stop screws on the secondaries a little to raise the rpm. Then close the primaries enough to gain mixture adjustment.
Just a thought.

 

[DonFitzwater]

Big cam? If the primary throttle plates are open too much to get idle speed it’ll uncover the idle passages and render the idle adjustments ineffective. The solution for that is to bump the throttle stop screws on the secondaries a little to raise the rpm. Then close the primaries enough to gain mixture adjustment.
Just a thought.

I did install a mild cam, nothing crazy. My best idle vacuum reading is 14 inhg currently.

 

[jhenderson]

Are the primary throttle blades uncovering the idle passages?

 

[DonFitzwater]

Are the primary throttle blades uncovering the idle passages?

I will know later when I pull the carb. I've got it running right now and I'll be pulling the carb tonight if time permits.

 

[Wayne M.]

There could be a clogged well too. I just went through this with one of my small engines that sat a while. I guess the fuel separated.

 

[DonFitzwater]

There could be a clogged well too. I just went through this with one of my small engines that sat a while. I guess the fuel separated.

This was a new carb in the box and I've been through it once already and it's clean as a whistle...........I am thinking Jhenderson is on to something. Will post later when I know more.

 

[Wayne M.]

Yes he surely is onto something. If you’re too far open on your primaries, there is something else to look at.

 

[DonFitzwater]

So, I pulled the carb and found that I'm running off the transition slots and not the idle circuits. I'm going to drill holes in the throttle plates so I can get enough air through the carb without exposing too much slot. I'll probably start with .070" holes in the beginning and go from there. Now I'm kicking myself in the rear end for not buying fuel injection from the start.

 

[Wayne M.]

I’d its not too late, try opening the secondary idle stop a tad. Maybe a 1/2 turn. That’ll allow the primaries to close more.

 

[DonFitzwater]

I’d its not too late, try opening the secondary idle stop a tad. Maybe a 1/2 turn. That’ll allow the primaries to close more.

It's not too late..........I was thinking about trying that since the carb is really easy to remove/install. I've got to turn wrenches on a Evinrude ETEC this evening but will hopefully have time to fiddle with the Dodge Saturday.

 

[DonFitzwater]

Ok, I adjusted the secondary stop 1/2 turn in and instead of Regaining primary idle circuit control I’ve lost all idle circuit control at all 4 corners. I have the idle mixture screws turned all the way in and she’s idling around 1350. No matter what I try I seem to end up in a situation where I’m exposing too much transfer slot as this engine is needing more air than the normal idle speed adjustment screw can give it.

I’m going to research my air bleed circuits and see if a change there might be better than drilling holes in the throttle plates.

 

[Wayne M.]

I’m starting to think you’ve got something else going on, like a good size vacuum leak. Time to get the brake cleaner out. Just be careful of the fumes that stuff makes.
This is where OBDII spoils you, but you’ve got no fuel trim to look at on this one.