Chevy Big Block Casting numbers

[elcamino]

Per many indentification books, no 3963512 were HD truck* engines, impossible due the design of block.

Only the high HP versions were 4 bolt, the 425 and 450 hp version per Chevy by the Numbers.

*The HD trucks block have "TRUCK" cast into the block behind the timing cover. I have seen this. Also, truck block means Medum and Heavy Duty trucks, not the average 1/2 & 3/4 light duty pickups, which use the same as the cars. They used 2 oil control pistion rings in these truck engines instead of 1 in the rest, making the cylinders 0.400 in longer.

According to Chevy by the numbers, all Tonawanda cast blocks will have a "T" cast into the surface. Tonawanda cast all parts used there.