Somebody help a brother out......

Rebuilt my idf's but need a baseline for setting the Idle Air adjustment (the one with the nut) back to it's correct location. I have an initial setup of 1 1/2 turns from notes when they were re-jetted 3 years ago but since this screw does not bottom out like the Idle Air adjusters I need to know where those turns are from??

Is it from the back of screws being flush inside with the throat or the front of the screws bottomed out on the nut? Or something else entirely?

Note to self to mark that kind of stuff in the future and to get that Weber book from Shoe. Oh wait I had someone else rebuild them....


Thanks in advance for replies...
Ken

You might find some help here. http://www.redlineweber.com/

Ken,
The idle air adjusters are the ones with the jam nut.
They're used to match all 4 carb throats to the one with the highest air flow.
Start with them all closed and only open them to match flow with a snail (or a really good ear for the sound of rushing air).

The mixture screws are the spring loaded ones.

I was going to correct that after EC posted the link and I looked at a diagram.

And Chris what is considered closed? That is what I am looking for. I have a snail. What are good numbers to look for?

Thanks for the reply, both of you!

Both the idle mixture screws and the air bypass screws should "bottom out." The air bypass screws, as Chris described are the ones with jam nuts and they get tightened down all the way till they stop. You can leave the nuts loose for not until final adjustment is done.

The idle mixture screws (the ones with the springs) typically start at 2 1/2 turns out from bottom, but if your notes say you had them at 1 1/2 before, then that's a good place to start, as that's probably near where you'll end up. Bottoming out those consists of turning them in all the way until they do not turn anymore. Then back off 1 1/2 turns.

The exact number is less important than having all 4 throats flowing identically at both idle and 2500rpm or so.
Whatever flow you get at your desired idle rpm is the correct number.

Just to define: 'bottom out' means just touching. As you gently turn the screw in you will feel it touch. That's All! It's pretty easy to wedge the tapered needle into the port and deform it, you're seating steel screws in soft casting metal.

No

Unless someone has honked down on the air bypass screws already, any leakage should be negligible; and the idle mixture screws just use the seat as a starting point for making your baseline setting

Harvey

When rebuilding IDF carbs it's good to closely inspect the idle mix screw seats. The brass seats may be damaged from past over-tightening of the screws, and cause problems setting the idle mix. The seats are replaceable if they are too messed up.