- Buick Ownership
I have a 66 Wildcat convertible with a 401 Nailhead with a 4 barrel Rochester carb. We are currently on a roadtrip through the western U.S. and Canada. For the first 3,000 miles the car ran great getting nearly 21 MPG. We started out in Phoenix (1100 feet above sea level) and have been as high as 11,400 feet in Colorado. I started getting an occasional stumble while driving along at about 65 after about a month on the road. I noticed a small wet spot on the fuel pump so changed it out thinking I might be loosing pressure. After installing the new pump, the stumble remains and the mileage has dropped to 12 MPG. I switched back to the old pump but the mileage is still at 12. Is there something in the carb that could have been damaged with a new pump and possible higher pressures from that pump? It's the only thing I've changed since beginning the trip. Before we left, I changed out the points, condenser, cap, rotor, plug wires, coil, plugs, fuel lines, fuel filter and all vacuum lines. The timing is set at 2 1/2 degress BTDC and the points at .016. Even now, the car starts, runs and idles great. It still has the occasional stumble but I can live with that if I can get the mileage back where it should be. Please let me know if you have any ideas since I'm currently in Alberta Canada and still have about 5,000 miles to go.