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-   -   High speed idle not high speed idling. (https://67-72chevytrucks.com/vboard/showthread.php?t=650903)

leddzepp 12-05-2014 02:25 AM
Re: High speed idle not high speed idling.
 
Quote:
Originally Posted by davischevy (Post 6936200)
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 12-05-2014 09:11 AM
Re: High speed idle not high speed idling.
 
Quote:
Originally Posted by mechanicalman (Post 6945182)
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 12-05-2014 10:43 AM
Re: High speed idle not high speed idling.
 
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 12-05-2014 10:46 AM
Re: High speed idle not high speed idling.
 
Quote:
Originally Posted by geezer#99 (Post 6945393)
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 12-05-2014 11:22 AM
Re: High speed idle not high speed idling.
 
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 12-05-2014 02:20 PM
Re: High speed idle not high speed idling.
 
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?!:lol:

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

slikside 12-05-2014 07:54 PM
Re: High speed idle not high speed idling.
 
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 12-05-2014 08:00 PM
Re: High speed idle not high speed idling.
 
Quote:
Originally Posted by mechanicalman (Post 6935618)
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 12-05-2014 08:29 PM
Re: High speed idle not high speed idling.
 
Quote:
Originally Posted by Fitz (Post 6945971)
This is why I run a Holley, not a Quadrajet!
Are you saying quadrajets are hard to work on? LOL :uhmk:

Doh! I just did.

mechanicalman 12-05-2014 08:30 PM
Re: High speed idle not high speed idling.
 
Quote:
Originally Posted by slikside (Post 6945959)
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 12-06-2014 02:00 PM
Re: High speed idle not high speed idling.
 
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?



Quote:
Originally Posted by Fitz (Post 6945971)
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 12-06-2014 03:33 PM
Re: High speed idle not high speed idling.
 
Quote:
Originally Posted by luvbowties (Post 6946800)
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
:lol:


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