I have a 350sb with an edelbrock 4bbl performance carb. I've had this setup for almost 2yrs. Recently at around 50mph the truck feels like it's running out of gas but it surges right back and this repeats over and over again until I get to over 60mph. Any suggestions?
Reading again more carefully, and I see the surge going away above 50mph.If the surging goes away when you open the throttle more it is hard to think insufficient fuel delivery--especially if you can open the throttle and run it up a lot or step into it when going uphill without running out of fuel, which will be obvious--you'll have to let up on the throttle to keep it running well.
The part throttle/light load circuit on these Edelbrock/Carter AFB is managed by the metering rods controlled by the attached piston with a light spring under it.At high vacuum the piston/rod is pulled down into the main jet leaning the mixture until throttle opening lowers the vacuum allowing the spring to raise the rod into a place of less effect on the jet size--richening the mixture.
Edelbrock has a tuning kit of several spring choices(different strength springs)and several rod sizes.This kit allows easy(?) changing of the mid range mixture without dismantling the carb.The power piston/metering rod/spring assembly jumps up to look at you when the little plate with one screw is removed.Two plates-one on each side of the primary(front)throats.
You say you have had this carb 2 years.During your ownership has this condition always been there or has there been a change in it's habits?
Also we have been experiencing an extended hot season which effects underhood temp and our beloved tubing headers don't help a bit.The AFB (aluminum four barrel)is a great heat conductor to the fuel it's handling and gasoline doesn't like to be heated much before being mixed with air in the carb.If sensitivity to heating is suspected an insulator or stack of gaskets under the carb may help and attention to fuel line routing can help.
In general, keep the engine /fuel/carb/incoming air/engine compartment cool.
