Engine idle RPM

[mshmodela]

After reading a thread on engine idle RPM, my engine was clearly idling too fast. I looked at Les Andrews book and http://www.model-a.org/idle_adjustment.html my Zenith 1 my idle rpm adjustment was all the way in so yeah idling fast...



I backed off the rpm one turn and wow, did that slow the engine down... I took my car for a drive and she sounds very smooth and balanced --and of course ran cooler... I do not a a tach but am looking to get one of those inferred ones to actually measure the speed. and as the experts here have posted on the subject, shifting is a easier... Thanks Ford Barn Experts...

[Mitch//pa]

wow Mike all the way in? that would make the idle screeeeaming.. set it up so its a little higher than getting ready to stall out with the lever in full retard very low. also make sure your return spring on the linkage is strong and not broken

[mshmodela]

Originally Posted by Mitch//pa

wow Mike all the way in? that would make the idle screeeeaming.. set it up so its a little higher than getting ready to stall out with the lever in full retard very low. also make sure your return spring on the linkage is strong and not broken

The rpm screw hit the stop, so I think yeah that's all the way in... so the arm cannot be made to turn towards the firewall, CCW as you look at the engine and slow the rpm down.. My new ownership ignorance... a little here and there.. Thanks experts...

[diomed]

I've also been playing with the idle speed on my car, it was way too high. I found that the return spring is bad, the idle adjustment screw won't fully seat against the stop. If I push it with my finger, the idle drops down really low. So, I temporarily put on a second return spring until I can replace the original one. The car does shift and run better.

[Mitch//pa]

just a quick word about high idle... i have numerous times found that i had to push the idle lever back as diomed mentioned and thats with a new return spring and nothing hanging up in the linkage...
the fix was to replace the throttle shaft with an oversize...

it was just to sloppy in the bore and caused the throttle plates to hang in the carb body.. no vacuum leak was really noticeable either but after changing wow what a difference

[mshmodela]

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Mitch,

OK thanks, it's going to take some playing on my part to learn what's best for the Idle RPM and Idle Air mixture on my car... My little change is better... I would also suspect that with the throttle full up (idle position) that if the linkage etc. are all ideal, when one pulls down on the throttle, the carb arm should move --yes? or is it common for some slop?

[Mitch//pa]

a little movement is good before it actuates the throttle... this way the lever cant hold the idle up if its down 1 notch

[mshmodela]

Flick on my engine...

https://www.youtube.com/watch?v=VGuaAt0rhjE