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#26 |
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![]() Join Date: May 2007
Location: Southern Cal
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Re: High speed idle not high speed idling.
x2
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1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man |
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#27 | |
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Join Date: Jul 2007
Location: Fall River California
Posts: 2,026
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Re: High speed idle not high speed idling.
Quote:
Thanks.
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#28 |
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Join Date: Aug 2009
Location: Bowser
Posts: 13,621
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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. |
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#29 | |
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Join Date: Jul 2007
Location: Fall River California
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Re: High speed idle not high speed idling.
Quote:
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#30 |
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Join Date: Aug 2009
Location: Bowser
Posts: 13,621
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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 |
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#31 |
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Join Date: Jun 2010
Location: San Diego Co.
Posts: 1,162
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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?! ![]() In fact, I'm going to check this out on my own truck next time I drive it.
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#32 |
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Join Date: Jun 2010
Location: San Diego Co.
Posts: 1,162
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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.
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1972 Chevy C-10, SWB, Fleet, 350/350, PS, PB, HEI, mostly stock, Survivor. ![]() |
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#33 | |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: High speed idle not high speed idling.
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#34 |
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Join Date: Jun 2014
Location: Glendale, Arizna
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Re: High speed idle not high speed idling.
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#35 |
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Join Date: Jun 2014
Location: Glendale, Arizna
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Re: High speed idle not high speed idling.
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#36 |
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Join Date: Feb 2009
Location: southeasternfoothillsofusa
Posts: 1,557
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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 |
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#37 | |
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Join Date: Jun 2014
Location: Glendale, Arizna
Posts: 1,642
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Re: High speed idle not high speed idling.
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