Engine stumbles under acceleration

[Grits]

1965 Fury III 318, automatic
Carb numbers looks like: 38482A and below the numbers is B5

Under mild acceleration runs great. Under maybe 1/4 gas petal acceleration engine stumbles, back off on petal and easy on runs great. At 40 MPH and above runs good and accelerates good under mild petal. Easy petal to floor accelerates good. I removed and cleaned carb and set both mixture screws. Vacuum to spark advance good. Vacuum advance is hard to move with distributor cap off. Used screwdriver to push on advance and moved but was harder to move that I though it should. Any suggestions?

Phillip

 

[traintech55]

Sounds like its time for a carb overhaul. This could be caused by one of two problems and with out being at the car, impossible to put my finger on which one. It could be float level to low, or worn / out of adjustment accelerator pump. A new kit and cleaning will fix this.

 

[bigmoparjeff]

Sounds like a carburetor problem. I've run cars with the vacuum advance disconnected with no driveability problems. Could be accelerator pump or accelerator pump check valve/ball. I would rebuild it and see what happens.

Jeff

 

[Buster Hyman]

First thing I would do is put in new fuel filters,especially if there is one at the carb inlet.

 

[69monaco]

How many turns are the mixture screws out ?

 

[commando1]

Sounds like its time for a carb overhaul.

STOP RIGHT HERE!!
That's all that needs to be done at this early stage of the game.
As usual, people tend to to run right up to step 12 from the beginning.
Trouble shooting 101.

Rebuild /replace the carb. It's an inexpensive (relatively) 2bbl. Report back. We'll take it from there.

 

[traintech55]

STOP RIGHT HERE!!
That's all that needs to be done at this early stage of the game.
As usual, people tend to to run right up to step 12 from the beginning.
Trouble shooting 101.

Rebuild /replace the carb. It's an inexpensive (relatively) 2bbl. Report back. We'll take it from there.

THANKS STAN.

 

[67Monaco]

STOP. I'd say he should start with the freebie stuff first. Or at least minimal spending anyway. Get yourself a vacuum gauge and re-time that engine. Two carb rebuilds before I figured out the stumbling was timing all along.

Use the light to get you to factory settings, then use the vacuum gauge to get the highest reading adjusting the carb with vacuum advance disconnected and plugged. I back down a little bit from max vacuum reading one or two points.

 

[Grits]

I ordered carb rebuild kit for local parts supplier. Just gave the year and engine and 2 barrel. When I pulled the carb, found out I had the wrong kit. That is why I just disassembled and cleaned with carb cleaner. I cannot read the tag very good. Can you tell the kind of carb and if the number are right. Looks lkie 38482 A and B 5 below this number.
Set both jets by ear. When idle started to slow or run rough, I backed off until engine ran smooth. Will check and reset timing.

Thanks so much for the feed back.

Phillip

 

[69monaco]

Turn both the mixture screws a half more open and tri again , you can,t do it right by ear.

 

[traintech55]

Turn both the mixture screws a half more open and tri again , you can,t do it right by ear.

To set the idle mixture correctly you will need a tach, and a vacuum gauge. Make sure you do both sides the same amount.

 

[Grits]

Timing was off. I reset to 10 BTDC. Still stumbles. Will get vacuum guage. Does anyone know the part number for this carb?
(38482A B5 )

Thanks
Phillip

 

[Grits]

New filter and line to carb.

 

[70bigblockdodge]

STOP. I'd say he should start with the freebie stuff first. Or at least minimal spending anyway. Get yourself a vacuum gauge and re-time that engine. Two carb rebuilds before I figured out the stumbling was timing all along.

Use the light to get you to factory settings, then use the vacuum gauge to get the highest reading adjusting the carb with vacuum advance disconnected and plugged. I back down a little bit from max vacuum reading one or two points.

This should be done, timing it to vacuum will compensate for loose chain and undo the emission initial timing.

 

[commando1]

STOP!
Freebiez
Then carb...

 

[Hansson72]

I good clean up can make magic to a carb.
That was all that needed to be done to my edelbrock on my 440 when it started to coff and spit at acceleration. I should start with that , adjustment to a dirty carb can be a waste of time...

 

[67Monaco]

STOP!
Freebiez
Then carb...

Then the thermostat.

 

[halifaxhops]

1965 Fury III 318, automatic
Carb numbers looks like: 38482A and below the numbers is B5

Under mild acceleration runs great. Under maybe 1/4 gas petal acceleration engine stumbles, back off on petal and easy on runs great. At 40 MPH and above runs good and accelerates good under mild petal. Easy petal to floor accelerates good. I removed and cleaned carb and set both mixture screws. Vacuum to spark advance good. Vacuum advance is hard to move with distributor cap off. Used screwdriver to push on advance and moved but was harder to move that I though it should. Any suggestions?

Phillip

The vac advance should not be that hard to move have you ever tried to move the cam plate? That's the shaft the rotor goes on, bet some of the problem is it was never oiled, easy check. Just try to turn the rotor, shouls move freely, if not it has rust on the shaft preventing mech advance, The open part on top of the shaft has or should have a felt pad for oiling, run into this constantly rebuilding them.

 

[Grits]

Thanks again for all the great information.

Got a carb kit and vacuum gauge. Rebuilt the carb. Retimed the engine to 10 BTDC. Vacuum advance does work right. Connected the vacuum gauge and got a steady 20 reading. The mixture jet screws I screwed all the way in and backed off 2 turns. Turning them in or out did not change the vacuum. It does not stumble nearly as much as before. It is a little harder to start. Maybe I need the carburetor replaced and a good tune up. Plug, wires, points condenser and distributor cap. Will try the tune up after Christmas sometime.

This really is a great forum

Merry Christmas
​

Phillip

 

[67Monaco]

Phillip,

Try taking a little timing out and see if it starts easier. If the idle mixtires screws don't change vacuum readings there's something else that needs to be investigated in that carb.