So I've been working on my Bronco trying to get it up and running, I've got the Offy C-series/Holley/hooker header in place and now I'm to the point that i need to tune the carb.

When I start it, the idle is high (not sure exactly how much more but I know the sound of a high idling I-6) and it sounds like there's a .22 in the pipe (open header at this time). Now I know its running lean I just don't know how to adjust the Holley.

Some help please....

To change the fuel mixture on a holley, you have to change the jets. All have a pair of primary jets.Some have a metering plate for the secondaries, while some have a pair of jets for the secondaries.

Drive the truck around a little, like you normally would and then pull a spark plug and look at it. If it is white or real light tan, you are lean and would need to go to a larger primary jet size. If the plug is dark, you need a smaller primary jet size.

After you get it how it should be, take it out and romp on it a bit so the secondaries open and re- read the plugs. If they are light, you need bigger secondary jets. If they are dark, you need smaller secondary jets. If you do not have jets for the secondaries, you will need to change the metering plate accordingly.

Also, you can change the spring in the vaccum can for the secondaries ( if it is a vac. secondary carb) to get the secondaries to open sooner or later. A lighter spring will open them sooner, a heavier spring- later.

There are also changes you can make if you have an off idle bog to the accelerator pump cam, or discharge nozzle. Most of the time you won't need to on a stock engine though.

What is the model number of the carb?

So there's no mixture screws like the Motorcraft and Edelbrocks have?


The only numbers I could find were as Follows:

List-1850-3
__1809

Thats how they were on the carb, didn't see any tags...

There are mixture screws on the side, but they only set the air mixture at idle. You turn them until you get the highest vacum reading, or the highest smooth idle.

1850 is a 600 cfm vacuum secondary 4 barrel.

surewhynot said:

There are mixture screws on the side, but they only set the air mixture at idle.

Click to expand...

Wouldn't that solve the popping issue?


And this carb came off of a healthy 390, which has me baffled about the install on the 300-6...

How long was it out of service?

Sounds like the accelerator pump may need a quickie rebuild... sometimes the conditions are just right for fuel to dribble in, causing the popping (unvaporized fuel) AND the high idle.
And this IS after warm-up, correct?

yeah, it'll idle high as long as its running, and the popping will get louder, also the choke isn't connected yet.

what all is involved with a Holley accelerator pump rebuild?

Here's a great article on that...http://www.fordmuscle.com/archives/1999/12/holley/index.php



Hope it helps!

One last question, is the power valve externally operated via a vacuum line or does it get its vacuum from an internal source?

Internal. It screws into the body, between the body and the metering block.

well, had to get a throttle ball kit so I could attach my throttle cable, lost the kit in the truck so I spent two hours cleaning the truck to find them (who knew you could get so much crap into an x-cab Toyota P/U).

Got the ball installed and figured out that one of the manifold stud holes was stripped out, and along with the fact that I had to use a carb spacer to get the throttle linkage to clear, maybe this is where the problem is.


I'll find out more after I get it tapped and threaded...

The spacer shouldn't affect much, unless your stud was so loose there was an air gap in there...
Don't forget to stuff a rag down there before you drill & tap. You going to Helicoil it too, to keep the stud size?

yup, Helicoil is the tool in hand. it was completely stripped to where I could lift the stud out...

So I took a couple video/sound clips of my Bronco running, I'm trying to get them loaded but on dialup.... YEAH RIGHT....


Anywho, I'm in the process of finding a way to load them into my photobucket account, unless someone knows of a faster place to load them...

okay, here it goes


here is one of the high idle, i tried getting it to kick down to no avail.





this is on warm-up, just at the end you hear it idle up because I hit the button not knowing it was going to do that.