Stomachs…. oil pans, what’s the difference? LOL


I have a 390 on my Dart with a lumpy cam, oversized valves, etc., and it uses every cubic inch of air that thing can serve up at 6000 +rpm. However it does not like low vacuum conditions at idle; mine idles at a loping 3-6â€￾Hg @ 7-800 rpm in gear with lash set at 0.024â€￾ to 0.028â€￾. Tighter lash causes a real bad lope, and 0â€￾ to 8â€￾ Hg swinging needle in gear with mixture running between lean and pig rich.


Conduct a compression test on your engine. Loosen the lash on cylinders a few thousands at a time on the cylinders that come in low, and re check. It is possible to even out compression between cylinders doing this. It also will lessen the lope which will give a better vacuum signal to carburetor; happy, happy, happy…


My engine had readings of 145 to 168 psi, and after playing with lash I ended up with all six at 163 psi. Tip: keep a battery charger on battery during test and tweak session. What you are doing is lessening the overlap between intake and exhaust event of each cylinder.


Reed is correct, get those books, study them, compare methods between the authors and read them again, and view the Holley stuff a few more times; it will slowly sink in.


Once you get the mixture right, engine will become perkier off the line, stop stinking (rich) at idle or surging (lean) under light throttle.


I have struggled with tuning my 390 for years, and finally installed an o2 sensor last year; it helped greatly.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

That and a vacc gauge viewed in the cockpit can dial any carb in within an afternoon and can suggest tweaks later as driving and weather changes...just don't used leaded fuel or leaded additive or it will not work.

All good Info. Thanks. I do want to read up and add this to my list of car components I am able to fix. My carb guy was able to dial it in pretty good. I do have the orange cam but still not sure of the position. I had other issues when the carb was installed that have been fixed. I was running hot due to radiator issues that have been fixed with a new radiator and a 180 psi water and 100 psi air flush of the block. It holds 180 degrees now in most conditions. Also had a small section of exhaust (manifold to firewall) that was still 1-1/4" that is now 2-1/4". A distributor that would not rotate far enough which has been fixed. As well as exhaust leaks fixed with Remflex. So with all other areas dialed in. it is running great. I will all posted on adjustments and learning. Thanks.

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'64 Valiant Conv V8
'72 Scamp /6 4bbl
'79 Adventurer SE