carter AFB troubles

[66dartman]

I have been working on my friend's 440 trying to cure a part throttle surge.
The engine is a 10:1 440 with eddy heads, mild crane (similer to 375 horse) cam, stock exh. manifolds and eddy performer manifold. It idles great and runs great wide open, but part throttle it surges. I have gone both ways with the metering rod springs with no improvement. I have jetted it down for our 5600 ft. altitude. Any ideas? The carb is a fairly new Carter 750.

 

[JimmieDart]

Sounds like you might need to change your step-up piston springs at the metering rods. A surge can indicate either a rich or lean condition, so the overall performance would dictate which way to go on springs, heavier or lighter. I think lighter causes greater sensitivity to vacuum, hence slightly richer mixture at part throttle cruise, but not absolutely sure. You can get a kit with assortment of spring weights and go from there. Nope, don't have part number, except for Edelbrock asst. kit.