High speed idle not high speed idling.

[leddzepp]

Originally Posted by davischevy

i wasn't kidding. I shot all the moving parts on mine with spray lube a while back, and it made a world of difference. If it don't help, what have you lost?

x2

[AirSpeed]

Originally Posted by mechanicalman

Speed-the choke linkage from the coil on the manifold seems to be dragging against the metal housing as depicted in your picture.

Just for grins and giggles, un-snap the sheet metal housing from the base and see if it frees up your choke.

The coil is clear, it moves freely, it moves through its travel without interruption, I watched it as it warmed up. The choke itself operates fine, it closes and opens as it should when the engine warms. The lever my finger points to seems to have drag to it, when I move it I can't see anything binding up, as I move it through its travel I feel friction till it's almost all the way down where it will suddenly drop. Just can't tell if this drag is normal. I guess a little lube wouldn't hurt it, I cleaned the carb as good as I could when it was off the engine, maybe it just needs some lube, I wanted to avoid putting to much oil on it, it took so long to clean all the old dirt and oil off it.
Thanks.

[geezer#99]

That liitle lever should have some drag on it. When it's up the high idle screw mechanism contacts it. Hard to see but it's there.
Your vac port that showed no vacuum is a ported vac port. Ported is above the throttle blades. Sees no vac until the throttle opens. Generally people assume the vac ports that are above the throttle plate are ported and the ones below are manifold (full time) but there are internal passages too which give you manifold vac higher up on the carb. Your choke pull off vac line is one of those.
Use carb/choke cleaner for cleaning the linkages and for lube. It doesn't leave a residue dust can collect on.

[AirSpeed]

Originally Posted by geezer#99

That liitle lever should have some drag on it. When it's up the high idle screw mechanism contacts it. Hard to see but it's there.
Your vac port that showed no vacuum is a ported vac port. Ported is above the throttle blades. Sees no vac until the throttle opens. Generally people assume the vac ports that are above the throttle plate are ported and the ones below are manifold (full time) but there are internal passages too which give you manifold vac higher up on the carb. Your choke pull off vac line is one of those.
Use carb/choke cleaner for cleaning the linkages and for lube. It doesn't leave a residue dust can collect on.

Thanks! That explains a lot, I'll play with it more today.

[geezer#99]

There's some good pics in here to see your choke stuff. Different choke style but yours is the same on the high idle.
http://www.vetteprojects.com/kstyer/quadrajet_4.htm

[slikside]

That "little lever" is the Fast Idle Cam I spoke of earlier. Are you checking the movement of it when the motor is cold? Again, that cam has notches on the bottom/lower end of it that contact your primary throttle assembly on cold starts. Each successive notch (lever falling) corresponds to a lower engine rpm while idling. This is the mechanism you are allowing gravity to move down when you "punch" the throttle to "step down" the idle. Those step downs are the notches on the bottom of the Fast Idle Cam.

I don't know for sure, but the next time your truck is fully warmed up (fast idle cam fully lowered) see if the fast idle cam moves freely at that point. If it does, that is not the issue, but if it doesn't it may not mean that's your problem. I just don't know. How's that for clarity?!

In fact, I'm going to check this out on my own truck next time I drive it.

[slikside]

So, with my truck fully warmed up, the fast idle cam freely moves around until you raise it about 1/2". Then, the bottom of the cam starts to engage the primary throttle shaft.

[Fitz]

Originally Posted by mechanicalman

A simple explanation would be to say you are likely lean due to less manifold vacuum because of the bigger camshaft. But, that's where "simple" ends because most every choke adjustment requires another adjustment to compensate as there are basically three adjustments and they all affect one another.

Let's start by telling us what choke style do you have.

Is it a round choke housing?

Does it have a metal coil covered by sheet metal bolted to the intake manifold?

Does it have electrical wires going to it?

Does it have a rubber hose on the housing going to a metal tube in the intake manifold?

This is why I run a Holley, not a Quadrajet!

[mechanicalman]

Originally Posted by Fitz

This is why I run a Holley, not a Quadrajet!

Are you saying quadrajets are hard to work on? LOL

Doh! I just did.

[mechanicalman]

Originally Posted by slikside

So, with my truck fully warmed up, the fast idle cam freely moves around until you raise it about 1/2". Then, the bottom of the cam starts to engage the primary throttle shaft.

Is that a stock intake manifold?

[luvbowties]

Quote:
Originally Posted by mechanicalman View Post
A simple explanation would be to say you are likely lean due to less manifold vacuum because of the bigger camshaft. But, that's where "simple" ends because most every choke adjustment requires another adjustment to compensate as there are basically three adjustments and they all affect one another.

Let's start by telling us what choke style do you have.

Is it a round choke housing?

Does it have a metal coil covered by sheet metal bolted to the intake manifold?

Does it have electrical wires going to it?

Does it have a rubber hose on the housing going to a metal tube in the intake manifold?

Originally Posted by Fitz

This is why I run a Holley, not a Quadrajet!

Hey, Fitz, let's toss a wrench into this mix by noting that Holleys also have the 3 major types of chokes as the quadrajet: manual, divorced, and integral[which receives heat from either a tube from manifold OR from within the carb itself]!!!

They both require science to understand and/or repair and adjust properly.
Sam

[mechanicalman]

Originally Posted by luvbowties

Quote:
Originally Posted by mechanicalman View Post
A simple explanation would be to say you are likely lean due to less manifold vacuum because of the bigger camshaft. But, that's where "simple" ends because most every choke adjustment requires another adjustment to compensate as there are basically three adjustments and they all affect one another.

Let's start by telling us what choke style do you have.

Is it a round choke housing?

Does it have a metal coil covered by sheet metal bolted to the intake manifold?

Does it have electrical wires going to it?

Does it have a rubber hose on the housing going to a metal tube in the intake manifold?





Hey, Fitz, let's toss a wrench into this mix by noting that Holleys also have the 3 major types of chokes as the quadrajet: manual, divorced, and integral[which receives heat from either a tube from manifold OR from within the carb itself]!!!

They both require science to understand and/or repair and adjust properly.
Sam