I'm having a difficult time with the q-jet on my '68 4-4-2. It's the stock 7028251 carb for the car and all of the innards are correct. What happens is that, at cruising speed, be it 30, 40, 50, or 60mph, the engine just starts cutting out for a second, then running strong again for 4-5 seconds, then cutting out for a second, then running strong again for 4-5 seconds, and so on. Start up is fine. Acceleration is fine. The float is set to spec. It just happens when you settle into a steady speed. Any thoughts on what might be wrong?

Right now we are thinking that maybe the spring we used under the power piston is either too weak or too short and that, at a steady speed when there is vacuum, the vacuum is pulling the power piston down enough that the primary fuel control rods temporarily shut off the fuel supply. But that's just an "educated" guess on our part.

Any thoughts on what we theorize or what you might have in mind will be greatly appreciated!

Randy C.