Community Forums:

Does anyone now how to tell an early B20 block, from a 74, from a 75 240 block, once its out of the car, the head is off, crank is out, etc.??????

I am guessing that some of the threaded holes in the 74 and 75 will be metric, but is there an easier way to tell.

Whether there are actual differences between the 74 and 75 blocks is not certain. I am told there are, including cylinder wall thickness, but its one of those things that I will believe when I see it. Thus part of the reason for wanting to be able to identify which is which and not rely on "it came out of a 74 so it must be a 74 block".

Even the year designations can be a little foggy as not all changeovers of all parts occurred on the same dates. Some old parts were used until they ran out and on the older cars, based on chassis number there is even some evidence of earlier cars getting later parts than slighty later cars. This is in accordance with the last in, first out, parts bin theory.

Does anyone actually know the answer?

John
V-performance.com