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Aka Force Fed Mopar
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Discussion Starter #1
Apparently on the AFB the choke has to be partially on for it to run right, even when fully warmed up. Hadn't never run into that before except one time, on a 2bbl. Guess I'll have to go buy a manual choke cable.

Wired the choke on partially and it runs pretty good. Still sounds like it's cutting back a bit at high rpms when driving, but I haven't really set the timing and all yet, and the choke may be causing some of that too. But at least it's driving around again now. I may swap the intake again, I have a Performer on an old 360 laying around. It has some oooooolllld 60's cast iron single plane on it now, it's actually made for the ooooooolllld WCFB 4-bbl. The AFB partially covers the heat choke hole on it.
 

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Sounds like the carb is too lean to me. :gr_patrio
 

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Slug-Gunner
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24 Posts
Vacuum Leak?

My first thoughts would be a "vacuum leak" either around the carb body, mounting base, base-to-mfld, or cracked vacuum hose somewhere near the carb or intake mfld. Take some brake cleaner and spray around these areas with engine at "fast idle" (around 1200 rpm).... if you hear a change in engine rpm, you located the general area, check closer to isolate it.

If this doesn't work then hook a vacuum gauge to an intake mfld port and monitor it. Then try pulling off vacuum lines one at a time and capping the carb/mfld side (both if they connect to each other). Don't forget the ones to the choke pull-off, vacuum amp/heater control vacuum switch, or brake booster assy. If you plug the "bad" hose/port, you should see an increase in mfld vacuum reading on the gauge.

The one to the brake booster assy has a one-way valve assy on it, usually located right at the point it enters the brake booster assy. If these go bad, they can also cause this condition, but usually more noticeable when you apply the brakes.

Your "choke partially on" to run right condition is indicative of a "lean" fuel mixture.... often caused by a vacuum leak. NO CARB should require a partial choke ON condition to run right on a warmed up engine with everything sealed up properly.

Let us know what happens.
 

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Aka Force Fed Mopar
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Discussion Starter #4
That's what I was thinking, I'll check that stuff out when I get a chance. The only vacuum lines I have on it are the PCV, the vacuum advance on the distributor, and the brake booster. I know the lines are good. I'll check the base gasket, I think I have some carb spray.
 

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Slug-Gunner
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Speed Dragon said:
That's what I was thinking, I'll check that stuff out when I get a chance. The only vacuum lines I have on it are the PCV, the vacuum advance on the distributor, and the brake booster. I know the lines are good. I'll check the base gasket, I think I have some carb spray.
:IDEA: Be careful using CARB SPRAY.... with certain brands, it can dissolve/lift the paint on the intake or valve covers, plus I've known it to dissolve/soften certain types of plastics/poly loom material. The BRAKE CLEANER works best, or even WD-40 will work, but I don't like the residue it can leave when exposed to heat.

BTW:
You still have a vacuum tap off the mfld to the heater control vacuum switch via the vacuum amp canister, unless you have a different HVAC system than the rest of us. ;) It's the diaphram inside the distributor vacuum advance, choke pull-off, vacuum amp, and brake booster valve that can also go bad and "bleed-off" vacuum. :dunno:
 

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Mopar Madness - Get it...
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Hey Speed.... Keep in mind the carb itself.
I went through 'carb-hell' a few weeks back...
Remember my post: "Well, Hells Bells, whoda' thunk??" (Page 3)

;) ;) ;)
 

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I have used a propane torch to find vacuum leaks before. Just open the valve and run the nozzle around areas of possible leaks. Do NOT light the torch!! Also if you have an electrical spark jumping it could warm things up. :gr_patrio
 

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Aka Force Fed Mopar
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Discussion Starter #8
No vacuum line for the heater controls, remember it's a '72 :) all manual baby. I'll check out some of that other stuff this weekend I hope.
 
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