Holley 1920 problem

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Slowswinger

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I bought a 72 slant six swinger dart with a holley 1920 that had been sitting for a couple years. It would start when cold and then die when it warmed up and the choke opened. I replaced all the vacuum hoses and checked for leaks. The fuel pump pumps good, I put on a new see thru filter (no junk so far), and disassembled the carb. There was a little gunk and varnish in the bowl which I cleaned out. I sprayed all the passages out with carb cleaner and none seemed to be blocked. I bought a carb rebuild kit and reassembled the carb. Now it does exactly the same thing, will start when cold but as soon as the choke opens it dies. If I back the idle mixture screw out til it almost falls out it will run rough with the choke slightly cracked closed (but still dies when the choke is opened that last little bit).

What do I check now?
Thanks
 
I took it apart again and found I did not have a pump return spring and on top of that broke the little dark red plastic piece in the picture. Now looking for parts or a complete working carb while I'm checking the valve lash.
 

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You'll probably have to find another carb to get that piece: I think it is a later model metering block. Or, fix the lever with epoxy if you can. You can get a complete rebuild from Mike's Carburator in WA state for $159; 'd trust that more than a parts store unit.
http://www.carburetor-parts.com/Holley-1920-Remanufactured-Carburetor_p_2934.html

It sounds like you have checked for vacuum leaks but that still sounds like your problem. Did you put a vacuum guage on it?
 
i made one out of steel once. and the lever on the outside, not easy but it CAN be done. OR find some one with one of the new 3 D printers.
 
Vacuum leaks were my thought too, so I replaced all the lines and checked by spraying carb cleaner. I will be ordering a vacuum gauge to see if it has enough vacuum or if I still have leaks somewhere else. I put a post in the wanted section but will think about making one from steel. This is frustrating, I finally got my first mopar and can't drive it yet, errrr. Thanks for the advise, I will post any progress I make.
 
Check the throttle shaft for play/vacuum leak. While its running at idle try to wiggle it and see if the idle changes. I have found this to be a problem on many 1920's
 
^^^ Good point.... if the throttle shaft is loose, the body needs to be rebushed, and the shaft examined to see if it is worn.

BTW, my point on Mike's Carb is that they seem to do a much better job in general to support carbs, parts and the home rebuilder, and based on the extra parts they send, their support, and the ready variety of parts, I would expect their rebuilds to be better than than the generic, assembly line parts house rebuilds. I have not bought one but did get kit parts and a new 1920 float from them with good follow-up support when the float was not the right one. Getting anather carb that is good takes that variable out of the equation.

The one thing I don't like about Mike's Carb is that you cannot call and speak to them... but they do answer their chat/blog thingie.
 
That lever is part of the "economizer". Similar to a "power valve" in 4 bbl carbs, it opens ball ports to richen the mixture at high manifold pressure (high throttle). My 69 slant idled like that for decades, thru many 1920's. I finally got a good 1920 and it ran unbelievably smooth. The metering block tends to clog internally. One guy here knows how to blow air pressure thru to unclog them.

You can get rebuilt 1920's on ebay. I found an almost new one in the trunk of an old M-B at an LA junkyard. Someone must have stashed it, assuming no M-B diesel owner would have an old Mopar. Sold it to slant guy here who lives nearby. His car was idling the same. The swapped carb helped but still shook a bit, which might have been ignition issues too. Before you get too deep, think long-term. Many here changed to a 2 bbl Super Six setup or a 4 bbl intake w/ 390 cfm carb.
 
I did think about swapping to a 2 or 4 barrel setup but didn't know what year intakes would fit a 72. Are all 225 slant 6 intake and exhaust manifolds interchangable?
 
All intakes interchange. Later EGR ones need a block-off plate ($15 ebay), or just leave the EGR valve on & closed (no vacuum). Of course, desireable intakes cost much more. A factory 2 bbl cast aluminum is primo, and similar price as a 4 bbl aftermarket unless you find a junkyard one or clueless seller. Some guys here lucked onto some 4 bbl ones on J.C. Whitney's site at a good price, but they were snapped up in an hour. Avoid E-beam welded alum intakes (late 70's-80's). They are extremely light, but many say they can be porous along the ugly weld line (looks like lava). You see the 2 split pieces when viewing the cylinder ports.

Factory Exhaust manifolds vary in the thermostat heat well, but otherwise interchange. After-market headers don't fit the shorter 170 engines.
 
Thanks Bill! I am going to take a walk at the wrecking yard and see what I can find.
 
I ordered a vacuum gauge from harbor freight and Dayton Carb had the plastic cam and a float so I ordered those. Everything should be here next Friday. Does it matter where the vacuum gauge is connected for the vacuum reading at idle or ????Thanks for the suggestions and help. Will post more when I get it put back together.
 
You could have a cracked intake manifold or a power brake booster leaking
 
The vacuum guage needs to be connected below the throttle plate; the ported vaccum line up on the side of the carb is not the point for general testing of vacuum leaks. There often is a vacuum port on one of the manifold runners used for vacuum accessories (like the heater vacuum controls).
 
Thanks Mopar Jimmie, I'll cap the line to the booster and see if that makes any difference and spray the intake to check for cracks.
Thanks nm9stheham, the gauge shipped, I'll get it hooked up and see what it reads.
 
Slowswinger said:
I ordered a vacuum gauge from harbor freight and Dayton Carb had the plastic cam and a float so I ordered those. Everything should be here next Friday. Does it matter where the vacuum gauge is connected for the vacuum reading at idle or ????Thanks for the suggestions and help. Will post more when I get it put back together.
Click to expand...
Do you mean Dayton Carb or Daytona carb?
 
My mistake, there actually called Daytona Parts ( 386-427-7108 ) and it was AJ that helped me, very helpful guy.
 
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