Engine runs poorly while driving, great while idling. Help!

[63Futura]

I am hoping that someone can help diagnose an issue with my ’63 Falcon. I have the 170 engine, with a Holley 1940 carburetor mounted on top, and a Ford-o-Matic bolted to the rear. The only engine modifications I have made are a Pertronix kit, as well as the headers that AzCoupe sells.

The car starts and idles great. Purrs like a kitten at idle. The problem arises when I actually drive the car (that is what it is for, after all). While being drive, the car will stumble from a stop just as the gas pedal is pressed, but as the RPMs build a bit, the car will smooth out. Also, the engine seems to want to run very rough, and it is a chore to keep it from stalling on me sometimes. I have had the carburetor rebuilt, and re-adjusted a couple of times, to no effect. I have also changed the plugs, as the old ones were fouled a bit. The car also wants to blow more smoke out the exhaust pipe when gas is applied than it used to, like it is running quite rich.

My thinking at this time, is that the carburetor is just worn out, that the accelerator pump in there is bad, and that I should just go ahead and replace the entire carburetor with a new one of the same model.

Would the symptoms that I have described above be an indicator that it is time to bite the bullet and replace the carburetor, or is there some other direction that I should look for getting the car to run better. Any suggestions that can be offered are greatly appreciated. Thank you in advance.

 

[hasa68mustang]

I had a bad carb. and it had a horrible idle, and was a chore to shut off. It would kick and sputter and like backfire out the carb when it whould decide it was going to shut off, the thing I found to make it turn off was if I left it in gear the rpms would be lower, but I had to remember to put it in park..... I had an internal crack, so when I put my Holley on it fixed it. It would also bog down a bit and sometimes stall when taking off, usually when cold. Dont think that helps you but oh well... It makes me look like I'm typing my poems in 6th period... Tommy

 

[Anonymous]

I'm thinking bad accelerator pump, and or poor or little advance on the dizzy.
cheers,
Steve-O

 

[80Stang]

Sounds like something I had with my setup. If your problem started just after rebuild, check that your throttle plate is put back the right way.

 

[Anonymous]

My similar experience turned out to be a bad Vacumn advance mechinism on the distributor. Idled fine but just wouldn't pull used gobs of gas, if babied could be coaxed into going down the road. The diaphram in the advance valve was rotted out. When i checked it with a light it seemed to be working fine -till i realized it was retarding -not advancing- when i gave it gas. A $12 ( and a patient desk guy at the parts store while we figured out which was the right part for my year falcon)part and it ran fine.

 

[SixFoFalcon]

My similar experience turned out to be a bad Vacumn advance mechinism on the distributor. Idled fine but just wouldn't pull used gobs of gas, if babied could be coaxed into going down the road. The diaphram in the advance valve was rotted out. When i checked it with a light it seemed to be working fine -till i realized it was retarding -not advancing- when i gave it gas. A $12 ( and a patient desk guy at the parts store while we figured out which was the right part for my year falcon)part and it ran fine.

I was just going to suggest this. Sounds like you aren't getting enough advance for the engine to accelerate properly.