This is an update to my orginal post (follow up) I have a 1965 chevy c20 with a 250 chevy inline 6. I have just bought it and only driven it twice, about 30 miles on both trips.It was running like a champ, real strong. On my second trip it drove fine the first 15 miles to my sisters house, then when i went to leave (20 mins later) i got a few feet out of her driveway and it just choked out. So it went from runnig great to not runnig good at all instantly.

What it's doing:

It idles a little rough, and when slow gas is applied through the throttle it revs fine as high of a rpm as you could go. However, if you press the pedal or the throttle arm quick to the floor it sounds like it is sucking air and backfires loudly.

When its driving:

In first and second gear you can limp it, but when i shift to 3rd it does not respond to the gas pedal and if its getting a load like an uphill it will eventual shut the truck off.

What i have done and checked:

1. I put a new carburetor on it
2. 6 new spark plugs
3. New fuel filter
4. New distributor
5. Checked the compression and they are all fine.

Over the last two or three days i have put the new distributor in it (with no improvement)and i have attempted to set the timing. I adjusted the timming by the book and then every other way possible; from switching it 180 degrees to changin the firing order from the rear vale, to completely strating over. Every time though, the only way i can get it to crank is doing it by the book. So i am completely confident its not a timing issue with regards to the distributor, at least not yet. I will note that wjen i use the timing light the mark on the harmonic balancer jumps eradically on the timing marks, to a point where sometimes its off the timing mark damper completely. Here is an additional question. If the timing gear set is off - could it allow the enigne to run good at slow application of throttle. That is to say that if the truck is idleing and i push the throttle slowly, i can rev the RPM's as high as i want and it sound like its runnig perfect; but if i were to run the truck on the road it will chug and die ecspecially if i make it to third gear.

It's better to have it and not need it, then it is to need it and not have it. "Woodrow F. Call"