Hey guys, new to the forum and also new to classic buick, and I'm wondering if i will have to rejet my Rochester 2GC that fuels the 340 in my beloved 67 skylark. I bought a set of Sanderson headers and I'm having a 2.5" dual exhaust run all the way out the back after the headers are on, and it already breathes through an edelbrock pro-flo filter. As far as I know the engine is stock, but she runs beautifully and has some impressive torque, at least to me. Would rejetting be necessary to accommodate for the headers and exhaust?
Possibly, the only real way to know would to use a wide band O2 sensor to see the air fuel ratio, or to test on a Chassis Dyno or at the track. If you are at the track, you could jet up and watch the trap speed. The 2GC doesn't use metering rods like a Q-jet. The power piston opens a power valve and extra fuel flows through calibrated restrictions. That means simply increasing jet size would increase fuel at cruise also. That might not be optimal. Maybe one of our Q-jet gurus here on the board could help. You may need to modify the restrictions for more fuel when the power valve opens. Try PM ing either Mark (carmantx) or Ken (techg8)
