Runs at FAST idle, not slow

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eandkatthebeach

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Hi guys - This is my first post.
I recently picked up a 1963 Valiant 200 Convertible, it was the 1st car I owned but it was a Signet back then, since Im a tad older now, I went for the convertible..... It has a 225 slant six, w/ a one barrel holley. As the title of my post states, I can get it to run at fast idle, but it won't run when the idle is lowered, I even had to take the idle spring out to have the set screw in as far as possible.
The car ran fine when I bought it, and after a couple months the engine started giving us idle problems, we found an intake leak, so i replace the intake manifold gasket. No more leak. I've checked the vacumm advance and it seems ok. I've changed the points,plugs, dist cap, rotor, and wires. I drained most of the fuel out and put new in. I also had the carb rebuilt by a carb shop. I tried to adjust the timing, but there is no timing indicator to check it against so I did it as best I can.
One thing I'll mention is that the idle mixture screw on the carb doesn't do much at all.
Any help would be appreciated - Thanks
 
Do you have a tach meter you can hook up to measure the rpm? At what rpm does it die? It sounds to me like the idle circuit in the carb isn't working, thus it only runs when the main jets flow. That matches your experience that the idle screws do nothing. A rebuilt carb isn't always fine. What model do you have? If the Holley 1920, I went thru 3 of those for 18 yrs, always idling rough, even with head jobs and finally a whole new long block and no change, until I got one that ran unbelievable smooth. I don't think anyone can rebuild the 1920 assured since it has hidden internals in the "metering block". I have a Carter BBS on my 64 Valiant slant and it looks more approachable, very similar to the venerable Carter BBD.
 
i agree with Bill 100% so just to reiterate, that whoever set up your carb didnt do a good job. it sounds like the float level is set too high and flooding out or the choke is out of wack. nows the time to learn how to rebuild those carbs. they are just about the easiest carbs in the world to rebuild and get set-up. there are very few parts to them. i would say it is definately a carb issue. if the mixture screw isnt doing anything, then the idle circuit is clogged or there is way too much fuel getting into it.
 
Muchas Gracias... for your thoughts, I appreciate the lead to the carb. I don't have a tach, just a timing light. I thot I'd bring it to a carb shop so it was done "right". I'm fairly handy(just rebuilt the lower unit on my Johnson 150 boat engine and it purrs....) so I think I'll order a carb rebuild kit and soak it for a few days. You guys recommend any in particular????

It has "LIST 2534" stamped on it, so I don't think it's a 1920. I forgot to mention I installed a new fuel pump as well.
Thanks again - I appreciate it. Will let you know how I make out.
 
That is a 1920.
Clean only the metal parts. Do not soak too long, it can erode metal. Follow the directions on the cleaner, and rebuild kit. Use compressed to blow out all passages. I use the small tube with can carb cleaner followed by compressed air as a final cleaning step, on all passages. However do not use cleaner on any gaskets or seals. As Bill said the metering body has internal passages. A vacuum source may work better to pull out a contaminant.

It is wise to use a new float if it is plastic foam. Do not over tighten the cover it can warp.

Check and measure all mechanical adjustments, float, idle cam, choke .....

If the car has a PCV system replace the valve and check hoses for leaks.
 
Thanks - good tips, will try them out.
Here;s a pic of what she looks like
 

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UPDATE: Ok - I got a carb rebuild kit from mike's carbs, did the rebuild and b4 I started the car, I disconected the fuel line from the gas tank, hooked up the fuel to some premium gas, used the cranking of the engine to purge the old fuel from the fuel line, thus ensuring I only had clean gas going into the rebuilt carb. Started it up, and same problem,won't maintain a low(er) idle speed. My son thot the fuel filter might be clogged, even tho I recently change it out, so I bypassed it and no change. Any ideas would be appreciated.
 
An old lawn mower trick sometimes works. Bring it up to a fast idle then quickly close the choke or seal the top of the carb. The engine vacuum might pull the contaminant out of the idle circuit. It will kill the engine, so turn the key off asap.

If that does not work, completely unscrew the idle mixture screw, and try it again.
 
Worth a shot I guess - thanks.
One of my buddies says it could be intake valve lash ??
But per Service Manual, it should be set a low idle - hahahaha - that ain't happening either
Will let u guys know what happens...
 
Ok - got home early today and my son helped me with the "trick" KitC gave us on trying to clear the slow idle circuit in the carb. Net, it didn't work, we even tried while pumping carb cleaner in the idle screw mix inlet. It just doesn't seem to be getting enuf gas at slow idle to run, just runs rough then stalls out. Didn't have enuf time to check the valve lash yet.
I have a gas station down the street and as much as I hate to ask the guy there to work on it - I'm running out of options....
Any other ideas?
 
Maybe try a bottle of propane. You could flow it in the carb throat and see if it will run on that at a slow idle. Squirts of starter fluid would work too. If not, you may have an intake leak somewhere, which you could also find with the propane (it will smooth out). If it does idle low and smooth with propane at the carb, that at least tells you it is the carb and not an ignition problem or bad cam.

Also, I just noticed you have been trying to screw the idle mixture screw in as much as possible. Don't go too tight or you can ruin the seat in the carb. Don't follow you on that. It usually dies because of too little fuel. Did you try going richer (unscrew)? Should be ~2 full turns out. It will also die if too rich, but usually dies smoothly instead of shaking, and the exhaust gets black first.
 
I've been careful about setting the air/mix screw, I've tried it at 1 turn out, thru 3 turns out and no help. MAtter of fact, I can take airmix screw out and it does the same thing. I think the idle circuit is still clogged. I don't know how - I had it prof''ly rebuilt and then I rebuilt it myself. It doesn't seem to be getting enuf gas.,,,,
I replaced the Intake manifld gasket also.
Not sure what u mean by running it on propane?
I believe if I spray starter fluid in it, it would run but will try it next time
 
Ok - I know it's been a while since my last post - but I've been working on my boat and enjoying the summer so haven't gave you guys an update on my situation. I got a spare carb of a different list # and jury rigged it up and it ran a bit better, so I went back to my original carb. Took it apart again - but this time I focused on the low idle circuit and used ACETONE to clean it along w/ compressed air. I took out the air mix screw, cleaned the screw hole w/ acetone, cleaned the small inlet inside the carb body, again more air, and held my finger over the slotted opening and blew in air again. It felt like something gave a bit as the acetone no longer dripped out the throat so I hooked it up and it ran like a charmer. Just wanted to give everyone an update in case this helps someone else having carb problems - love that acetone!!!
 
Congratulations, and thanks for the new post with the report. I'm no carb guy, so maybe some of the previous posters can add some insight about what was causing the original condition and the cure.
 
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