Is it possible you have a loose wire or a faulty guage?
SPEED SAFE, AIR RAM
Im putting together a .040 455 with Edelbrock heads (72cc), Eagle Rods, FLAT top J&E Pistons for 12:1, Harland sharp roller Rockers, Fluidampner, Edelbrock Performer RPM intake, and 750 Demon Carb. "GOT TRACTION"