Hi There Scotty. My truck is a 1950-53 3100 Chevy thriftmaster. It has a 350 small block engine. I believe it is from a 1977 Camaro. The engine starts and runs well. My issue is that when I rev it at one point it begins to shudder ( i don't have a tachometer on so i don't precisely know the RPM), the shudders stop when i lift off the gas pedal. When engine is at idel without revving it doesn't seem to shudder. The engine seems to be calm and in sync at idle. I also notice this shudder when i accelerate down the road. I am thinking of swapping the harmonic balancer, spark plugs seem to be ok, and carb has been recently cleaned and seals/gaskets are new. Please help !
Yeah try that first. You might also want to pressure test fuel pump. Low fuel pressure can do that and realize something that old cleaning the carburetor might not cut it. It might need it rebuilt it replaced
