Replaced the carb no vacuum leaks, it idles fine it park, put it in gear and it seems like it wants to die, sometimes it does sometimes it doesnt.
My car has an automatic transmission.
Hi there. It is common for an engine idle to decrease when in gear, as the application of the flywheel and transmission creates an additional drag on the motor. If it drops 100 to 200 RPM, then it should be OK. If it drops more than 200 RPM, you might have to adjust the idle screw or might have an internal issue with the carburetor such as a float bowl that is not functioning correctly. It also depends on whether or not the carburetor you purchased is correctly sized for the intake manifold and engine for your C10. You might want to first call the manufacturer of the carburetor you purchased to seek their advice on this issue.