Rough idle at start.

[brown7373]

My 72 C-10 has a GM 350-290 crate engine I installed 3 years ago and has run just a little over 3000 miles. It replaced the original 350. It has run fine until the past 6 months of so.

At start-up after it sits over night or longer, it seems like it is only running on 4 or 6 cylinders. It does this for 10 or 20 seconds, then it quits and smooths out. Once it smooths out, it runs fine and doesn't do it again.

At first I thought maybe sticking lifters, or not pumping up, but that seems unlikely on a new engine. Might it be something electrical, such as a bad coil or cracked distributor cap or rotor. Another thing, which has been since I installed it is HORRIBLE gas mileage. With the original 350 it got 11-13, but this engine gets only about 7!

At install, I rebuilt the Q-jet, installed new plugs and wires and a new distributor with Pertronix.