Holes in piston?????

[Paul Singleton]

Hi Bob, it could be lean fuel mixture on the affected cylinder causing pre ignition or excessive combustion heat. I think excessive rpm of the engine could also be a factor. The Chevrolet city delivery trucks I worked on many years ago had a vacuum governor between the carburetor and intake manifold that limited engine speed to between 3200 and 3400 rpm. These were 235 sixes. If I recall the governor was a hoof brand governor. It may be wise to install one if you could find one. One of the trucks you got from me had a 235 engine laying in the box, it may have a governor, the engine was from a delivery truck.