whats the differences between 318-1,318-2 and 318-3

[tiffy's W150]

Hello guys........
whats the differences between the 318-1 ,318-2 and 318-3 ? I was checking out my 1983 W150 and found out my truck has a 318-1. I wondered what that means ?
thanks guys...... Tiffany

[Chewie]

The numbers designate an engine service option.

318-1 is the standard version found in cars and later 1/2 tons..
318-2 is the semi premium version, built a little heavier for working trucks.
318-3 is the full premium version for medium trucks.
The designations can be found on any engine: 318-3, 225-2, 413-3, etc.

[2x1972]

Is there any difference mechanically?

[USN78W150]

318

The 318-3 is supposed to have a forged crankshaft and double roller timing chain. I have never attempted to verify that, though.

[DODGEBOYS]

whats said above is semi right to a point / the 1 - 2 - 3 on the block was meant to mean the NICKLE content of the Cast Iron they made the block out of / the higher the number the better [stronger] the block was and could be built better [ statement above] with heavy duty parts / more nickle content meant less core shift and a straighter block