Problems with Holley 1920

[1969_Valiant]

Hey all. I'm trying to get my ride on the road again and it seems I have a big problem.

Last year I rebuilt my carb at my friends shop, under the supervision of certified mechanics, using instructions from the Plymouth factory manual(I have purchased one of my own since). I bagged and labeled all of the parts and was very careful to follow all directions. When I had any questions or problems, I asked one of the mechs.

Upon reassembling the carb, it eventually started and ran without any probs. I didn't make any adjustments at all. I drove it home 5-10 miles wihout any problems. It wasnt inspected, but I ran it periodically to keep everything from cracking, seizing.....

Each time I ran it, the car got worse. It would eventually start sputtering and when I would add any gas, it would almost stall. Eventually I would let it idle to the point where it would cut off. When I would start it, the same thing would repeat. Eventually, I had to let it sit for hours until it would start again.

I guessed that the carb was running rich and needed adjustment. I asked my mech friend and he said the choke may not be opening up. I ran it to see and it never completely opened by the time the car cut off. I checked the choke valve and the cam and neither will react to the other. There is a piece of linkage in between that doesn't seem to do anything, and I'm guessing that is the problem.

I have attached photos. If you look at the point of my key, that is the piece in question. Let me know what you think, and if you have any other ideas. Thanks again for all of the good info. Many of you have been a big help in the past.

 

[BillGrissom]

You are pointing to the linkage of the "choke pull-off". Its purpose is to pop open the choke slightly as soon as the car starts. Review the manual. You set the opening to a drill bit size. The rubber diaphragms often leak because they don't like carb cleaner. Test it with a vacuum pump. A new one costs ~$10 if you can find one.

You can adjust the theromostat itself (rod coming in from the right). Remove it from the exhaust well and you will see rich (R) and lean (L) marks, where you rotate the spring tightness. The choke should be closed fully when the engine is cold, even if 70 F, but not real tight. Sounds like yours is set too tight. The old mechanical sensors like yours are hard to adjust well, and the choke stays on too long. If you can find a later electric-assist one for a slant, that would work better, but be sure to get the thermal sensor that goes with it. There was also an after-market version (thru J.C. Whitney), but it didn't work well for me on my 69 Slant years ago, but then I didn't understand the choke pull-off then either (mine was bad).

 

[KitCarlson]

In the absence of a vacuum pump it is possible to pull the hose from the end of the choke pull-off, then depress the part that goes to the linkage towards the pull-off, then cap the end where the hose connected (vacuum port) with a finger. Release the linkage part, it should stay in, then go out when your finger is released from the vacuum port. This tests to see if a leak exists in the pull-off diaphragm.

If the pull-off tests good, and you did not replace the float in the carb rebuild it might be a gas logged. A defective float can dry out and run fine after a rebuild, then become gas soaked where it does not float, resulting in way too rich of mixture. Typically this happens in a few days.

 

[1969_Valiant]

Thank you for the info guys. I'll definitely look into all of that. I forgot to mention that the car used to have a nice high idle on cold starts, then drop when warm. Now the idle is always low even from a winter cold start. Does it sound like this is all related to that choke pull-off valve? Once again, thanks for your time with this. You guys are awesome.

 

[slantsixdan]

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. Sounds like your whole choke system needs a careful going-over to make sure everything is hooked up and adjusted correctly; see also here.

 

[1969_Valiant]

Thanks Dan. I took a look at the one page, and the choke operating link is what I was describing. I've saved all of the info. I will try and get my friend to help me with this stuff. Thanks again.