Slowly....dying...

[PrescottJeff]

Old carbureted cars constantly change. You could have any number of things going on. I didn’t see what we are working on so for now I’ll assume you have electronic ignition and we will say that’s good. I suggest you find the 2 air/fuel adjusting screws under the front edge of the carb. DON’T just start turning them, instead turn them both 1/8 turn counter clockwise (rich) If it runs better you’re good. If runs worse go clockwise 1/8 to get back to your starting point plus an additional 1/8 in (lean). Again if better you’re good. If not 1/8 CC puts you back to your starting point and you have eliminated a minor A/F adjustment. I can’t tell you how many cars I’ve fixed where some weekend warrior just started turning screws until it’s all F’ed up. If you’re careful about knowing how to get back to where you started and not making huge changes you can learn a little about your car.

 

[Demonic]

I had a bad coil that gave a weak spark after about 30 run time. If the car hot-soaked it was worse, but if I parked it with the hood up for 30 min, it was good till it heated up again. Probably not you issue.

 

[kaj750]

You may have leaking n/seats in the carb. While cruising that extra fuel gets used up & you do not notice any problems. At idle, where very little fuel is reqd, it runs rich, idle rpm drops, worse the hotter the engine gets. Remove carb top & check n/seats & for fuel logged floats.

I suppose that's possible but the carb is only about a week old. Not that I'd rule out a manufacturing defect.

 

[WileERobby]

And your vacuum gauge readings during all these symptoms is...........

 

[twecomm]

Not necessarily suggesting this is your idle problem but... For whatever it's worth, I run with a Edelbrock 1406 on my 383, 727 automatic 66 Charger. Tail end of summer, all of a sudden idle became very erratic. To keep engine running in gear, had to set idle way higher than normal and even then idle RPM's was never stable and repeatable day to day and just all over the place.
Looked around on the Edelbrock web site and there was a video suggesting that erratic idle was dirt or something contaminating the idle circuit. The suggestion was to back out and remove both idle mixture screws and shoot compressed air into the idle mixture screw holes on the carb body to remove any contaminates then replace the screws adjusted to a rough setting of 1 & 1/2 turns from full in position. That totally cured my problem. I went back and did a fine tune idle mixture with vacuum gauge & RPM gauge. Been fine ever since.
Also, when I first bought and unpacked the 1406, I removed the top horn casting and checked the float levels, they were way off right out of the box and required adjustment as directed in the owners manual. My theory was that since they just flop around during shipping, if they were set at factory they don't necessarily arrive to you at the correct float settings.

 

[kaj750]

And your vacuum gauge readings during all these symptoms is...........

Last was around 8 or 9, I believe, with my mild cam. Haven't re-checked in a few days, though. Couldn't hurt.

Since my original post, I haven't had time to mess with the car.

Not necessarily suggesting this is your idle problem but... For whatever it's worth, I run with a Edelbrock 1406 on my 383, 727 automatic 66 Charger. Tail end of summer, all of a sudden idle became very erratic. To keep engine running in gear, had to set idle way higher than normal and even then idle RPM's was never stable and repeatable day to day and just all over the place.
Looked around on the Edelbrock web site and there was a video suggesting that erratic idle was dirt or something contaminating the idle circuit. The suggestion was to back out and remove both idle mixture screws and shoot compressed air into the idle mixture screw holes on the carb body to remove any contaminates then replace the screws adjusted to a rough setting of 1 & 1/2 turns from full in position. That totally cured my problem. I went back and did a fine tune idle mixture with vacuum gauge & RPM gauge. Been fine ever since.
Also, when I first bought and unpacked the 1406, I removed the top horn casting and checked the float levels, they were way off right out of the box and required adjustment as directed in the owners manual. My theory was that since they just flop around during shipping, if they were set at factory they don't necessarily arrive to you at the correct float settings.

Couldn't hurt. I'll try anything at this point. I did have to run it without an air cleaner for a while. Who knows what got in there.

 

[oldbee]

8-9” of vacuum? With a “mild” cam?!! Oughta be north of 15” vacuum.

 

[kaj750]

8-9” of vacuum? With a “mild” cam?!! Oughta be north of 15” vacuum.

That could be a problem then. I don't remember the exact number, but it was nowhere near 15

 

[Geoff 2]

Just wasting time until we get more info. Could have wiped cam lobe....& many other possibilities.
What is the vacuum at idle?

 

[kaj750]

Just wasting time until we get more info. Could have wiped cam lobe....& many other possibilities.
What is the vacuum at idle?

Cool. Thanks.

 

[1967coronet]

Well, just me but if that engine is running bad after it's warmed up and the outside temp is cool.
I would check the choke operation.
If it's electric I needs switched 12 volts and a good ground.
Manual , make sure the cable is letting it function correct.
If it's unhooked make sure the plate stays open and not sucking shut.
Once it's starting to run ruff leave it idle and pull the lid & see were the plate is.

 

[kaj750]

Well, just me but if that engine is running bad after it's warmed up and the outside temp is cool.
I would check the choke operation.
If it's electric I needs switched 12 volts and a good ground.
Manual , make sure the cable is letting it function correct.
If it's unhooked make sure the plate stays open and not sucking shut.
Once it's starting to run ruff leave it idle and pull the lid & see were the plate is.

I will recheck the choke, but yesterday looked fine. Power and ground are good.

FINALLY had a chance to get out to the car tonight. Here are the plugs starting cylinder 1 going to eight.
One of them looks to have oil on one side which makes me think I have a leaky valve stem seal.
Hopefully tomorrow I will find time to do more testing. It seems I lost my vacuum gauge so we'll have to go get another one.

 

[Geoff 2]

Plugs should be a '5' heat range in NGK.

 

[kaj750]

Plugs should be a '5' heat range in NGK.

These are Champion, or something like that.
I just put NGKs in. NGK V Power Copper Spark Plug 3332.
I'll look up their heat range, but they were listed as OEM equivalent for my engine.

 

[Sparky Anderson]

Go to YouTube to Dead Dodge Garage and describe your problem to Jamie, he will point you in the right direction!

 

[kaj750]

Go to YouTube to Dead Dodge Garage and describe your problem to Jamie, he will point you in the right direction!

I'll give it a shot. Thank you.

 

[RJRENTON]

Plugs should be a '5' heat range in NGK.

Or specifically: Champion RJ-12YC or Autolite AP-85 or AC R43S or Mopar P34P OR I use either Champion UJ-11G non projected center electrode gold Palladian center electrode OR Champion HO-8A non projected center electrode platinum fine wire, cut back design. Both are excellent design, broad heat range. 3/8" reach......smooth starts, excellent idle properties (@ ~ 1200 rpm)......there is nothing that says "you must use projected center electrode plugs".....I use what runs best.......regardless of what the general consensus says.....including what my "buddy" thinks........
BOB RENTON

 

[72RoadrunnerGTX]

Go to YouTube to Dead Dodge Garage and describe your problem to Jamie, he will point you in the right direction!

Seriously? You believe there is more experience/knowledge on that YouTube channel than there is here? The combined experience of the handful of members who have already responded to this thread alone far out paces that guy. Heed the training/experience disclaimers he adds to each one of his videos.

 

[Mbrew]

Hi
So dont know how cold it is where your but your problem sounds like carburetor icing .
Was a common problem in the old days .
It will smarten up once under hood temperatures have risen .
Run for awhile shut it off for 15 minutes and start it up again.

 

[kaj750]

Hi
So dont know how cold it is where your but your problem sounds like carburetor icing .
Was a common problem in the old days .
It will smarten up once under hood temperatures have risen .
Run for awhile shut it off for 15 minutes and start it up again.

The car doesn't run any better after being off for a few mins. When I park it and come back out, it's the same.


Update: So far, I've tossed in the new plugs and blew air through the idle circuits. It may be doing marginally better. I then made sure the idle was at a solid 850 (A/T trans).
The car still stumbles while tipping in throttle but does great when I punch it LOL. I don't like the car stumbling as I'm trying to pull into traffic like a normal person, though. This is the exact same thing my Holley did and why I got rid of it.
I verified the choke and it's completely open once warm.
Also, I am now seeing the idle hunt a but while in drive and at a stop. Maybe it's been doing this the entire time and I just didn't notice. Not like vacuum leaks that I'm used to, though. This is much slower. In gear, the idle drops to about 700ish (I wasn't wearing my glasses LOL) then, after about 5sec, will drop a bit for 3-5sec then back up. Repeats.
So... maybe the car has developed a vacuum leak, though the carb is new, installed just a few miles ago, and all vacuum lines are new AAAAAAND the car ran perfectly just a couple weeks ago.
I thought carbureted cars were supposed to be simpler than newer stuff? On the bright side, there's only three vacuum spots to check. If no luck, I'll pull the carb and try a new gaskets between the intake, heat shield, and carb. If still no luck... then I don't know. ....