rough running break-in period
It was not as easy as only replacing the cylinder heads. They needed the camshaft timing & engine specifications checked.
Still to this day a set of pistons for an American V8 will vary in size .020 inch.
Sloppy piston sizing ?
Selected as a set only by weight ?
Building a loose engine to bypass the rough running break-in period ?
"That is what the rings are for" logic ?
The engines were beyond worn out specifications, at brand new !
The engines cylinders had to be bored for oversize pistons and rings and each piston custom fit to each cylinder, as any good engine rebuilder would do.
Poor fit pistons, a common reason for engines that burn crankcase oil.
Those Impala's might still be in a museum, someplace.
Like you could say about a marriage, if it is a poor fit the rings will not keep it together.
