Poor idle

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RichardR

RichardR

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Wasaga Beach, Ontario, Canada
Hey,
I had a post about fuel pumps, thinking that was my issue, but the pump pumps well. I took the carb off and cleaned it out, rebuilding it with a Walker kit. Put fresh gas in the tank, crank it until the new stuff was in the filter and connected it all back up. Started up great. No issues at all. Was running well.....until engine got hot and it started slowing down. Idle mixture screw did nothing, I actually had to close it almost all the way for it to not die and idle super low. Still uses points.
Any ideas?
Things done:
Cleaned and rebuilt carb
New lines
New filter
Timing checked and adjusted
Valve lashed checked and adjusted
New wires
New plugs
I don't think this is the original carb. Original is in the trunk and is super poor shape. This carb though has a weird jet that can be unscrewed from the outside, located right about where the horn tapers in. Anyone know what that is? I included a picture to show it.

A little more info: it blows a bit of black out of the exhaust when revved

Thanks

IMG_20180429_1957331.jpg
 
RichardR said:
Hey,
I had a post about fuel pumps, thinking that was my issue, but the pump pumps well. I took the carb off and cleaned it out, rebuilding it with a Walker kit. Put fresh gas in the tank, crank it until the new stuff was in the filter and connected it all back up. Started up great. No issues at all. Was running well.....until engine got hot and it started slowing down]
Click to expand...

Does it pop or sputter at all while it's trying to die, or just slow down until it ends up stopping?
 
Pull carb and check fuel level after it dies. Youll have to be careful and try not to disturb the fuel level. Sounds like its flooding. try this: put your hand over the carb when its starting to die to richen it . Does it help or hurt it? if it kills it outright, your probably rich and your needle seat is hanging. If it helps, your lean. I have a carb with a glass fuel bowl cover, what a great idea. Wont start, check the glass! Seems a 1920 could run a glass cover if you just cut a hole in an old one and bonded the glass in with fuel proof epoxy.
 
RichardR said:
I opened up the lash before winter. It was too tight then.
What should the float height be? Is my float too high?
Click to expand...

If the float level looks good and there is plenty of fuel change the condenser.
I have seen them do that before, and they are cheap to replace.
The reason I asked about sputtering or anything was because of it.
Some think they work or they don't, and that's not the case.
 
TrailBeast said:
If the float level looks good and there is plenty of fuel change the condenser.
I have seen them do that before, and they are cheap to replace.
The reason I asked about sputtering or anything was because of it.
Some think they work or they don't, and that's not the case.
Click to expand...

I may just replace it all with electronics instead
 
Update: I followed slant six Dan's set up for setting up idle, car started great, fast idle works good, started to idle decent. Drove it, accelerated ok, but after I stopped the idle dropped to the point where the oil light started flickering on and off. Then drove it home and it still idled poorly, slowing down and speeding up slowly and by this time the accelerating started skipping and bogging a bit.

Idle circuit does work now though. Out of the exhaust you can hear it go pfft pfft rumble rumble pfft pfft

Any thoughts?
 
Sounds like a lean miss? Fuel or ignition....a lean mix is hard to fire so that may be your miss. Use manifold vacuum.
 
pishta said:
Sounds like a lean miss? Fuel or ignition....a lean mix is hard to fire so that may be your miss. Use manifold vacuum.
Click to expand...

That would make sense since the exhaust is sooty sorta see the odd wetness come out and making pfft noises.

Which nipple is best for manifold vacuum?
 
odd wetness is condensation, not an issue. anything off manifold or BASE of carb under butterfly valve. Sooty sounds rich...? what color is smoke, white, black, does it smell sweet (coolant leak) ? do you have another coil/condensor you could throw on there.
 
pishta said:
odd wetness is condensation, not an issue. anything off manifold or BASE of carb under butterfly valve. Sooty sounds rich...? what color is smoke, white, black, does it smell sweet (coolant leak) ? do you have another coil/condensor you could throw on there.
Click to expand...

It's black. I could really tell when the snow fell to contrast the colour. I don't have an extra coil or condensor. I'm going to order an upgrade kit for it.
 
pull the plugs now. Black smoke is rich (seems like were going around in circles now) Still could be a ignition problem as you have unburned fuel in the exhaust.
 
Try jumper'ing straight from BATT+ to coil+ while it is running. If the idle smooths out, the problem is your ignition system, i.e. too much voltage drop thru key, bulkhead, and ballast. Don't leave long like that (< 1 min) or your coil will overheat, and don't leave jumpered with engine not running. If you do go electronic, get one that eliminates the ballast (Ignitor II & up, GM 8-pin HEI, ...).

Re checking fuel level, I recall the Holley 1920 manual says you can temporarily remove the "economizer" (3 screws) to measure the level. That part is similar to a "power valve" in Holley 4 bbl carbs. It richens the mixture at higher throttle. Manifold vacuum holds it upward (idle & low power). As you press the throttle, the spring pushes it down to open 1 or 2 balls to flow in more gas. I had bad luck w/ Holley 1920's in my 69 Dart, going thru 4 over decades before I found one which made it idle like a new car. Before that, it would idle rough and stumble off the line from stop-lights, wanting to die if you didn't pump the pedal to give it accelerator pump shots. Very bothersome.
 
BillGrissom said:
Try jumper'ing straight from BATT+ to coil+ while it is running. If the idle smooths out, the problem is your ignition system, i.e. too much voltage drop thru key, bulkhead, and ballast. Don't leave long like that (< 1 min) or your coil will overheat, and don't leave jumpered with engine not running. If you do go electronic, get one that eliminates the ballast (Ignitor II & up, GM 8-pin HEI, ...).

Re checking fuel level, I recall the Holley 1920 manual says you can temporarily remove the "economizer" (3 screws) to measure the level. That part is similar to a "power valve" in Holley 4 bbl carbs. It richens the mixture at higher throttle. Manifold vacuum holds it upward (idle & low power). As you press the throttle, the spring pushes it down to open 1 or 2 balls to flow in more gas. I had bad luck w/ Holley 1920's in my 69 Dart, going thru 4 over decades before I found one which made it idle like a new car. Before that, it would idle rough and stumble off the line from stop-lights, wanting to die if you didn't pump the pedal to give it accelerator pump shots. Very bothersome.
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Thanks. I ordered an igniter 2 and a new coil as well as a new pump. I did notice that the fuel level in the filter drop as it got hot.
 
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