I'm having a drivability issue with my 72 D100. 318 2bbl, fresh carb, and ignition. When I step on the gas, I get a hesitation before the truck goes. This happens when I first start out, and when I step on the gas on the road. It doesn't always do it tho...which has me puzzled. My Duster also did it, but has a very different combination ( 340/727/Holley 4bbl ) I was thinking it was an accelerator pump problem, or a distributor advance issue...

Any ideas?

j

 

Does it do it only from a complete stop or even while you are moving (as in coasting but not on the gas)? What have you changed if anything since the problem accurd?

I would think that you have a problem with your timing advance but I could be wrong.

 

sounds more like a accelerator pump issue
have you double checked everything on the distributor though?

 

I agree on the accelerator pump most likely culprit. And it's just a personal bias, but I hate that 2bbl carb, I've never had one work right for me. Guess it's probably just that a 4 bbl has more flow to forgive my mistakes

 

dont forget the possibility of a power valve being set for the wrong vaccum. my fifth ave had a problem like that but the accelerator pump was fine and found out it was the power valve. i noticed that my car did have a lot more bottom end torque with the 2bbl i used to have on it though.

 

Thanks for the replies folks. The hesitation happens off idle, like at a red light, or crusing down the highway and I step on it to either catch up with traffic, or go to pass someone. Problem is, it doesn't always do it. I want to switch over to a 4bbl, but want to make sure the gremlins are out of the picture first.

j

 

Swapping to a 4 barrel will probably help it out, as long as the carb is set up right, your timing is dead on ***** accurate, and you have no vacuum leaks.

 

Had the same issue with our 1970 383 Power Wagon. While changing the water pump I thought it was a good idea to check the timing chain. Often "while you are in there" works. The original nylon gears were almost gone and the slop was about 3/4". For 70 bucks I now know the factory timing setup is gone and I will not have to concern myself with that again.

BTW the truck wears the factory paint, almost no rust from AZ and 86k miles.

 

its a lean idle circuit.