Valve cover tag 401.. Decode..??

The 401 I have is from a 1972 Javelin AMX. But it was built in 71'.

I've always wondered if the 72' cars built in the last months of 71' were rated at the 71' horsepower ratings and if they were built with the 71' compression ratio?

BU1 is correct on the tag decoding. 1959 starts with "1" as that was the first year that coding was used. No zero was used through 1979, and the code repeated every 9 years, so 1 could be 59, 68 or 77. So you have to know a bit more about the engines, as in what sizes were made what years and what size/type you actually have.

See the asterisk (*) by the 4th digit engine size? It's there for a note that says the engine code may be different from the VIN engine code. I don't recall what specific engine codes are different, but they don't always match the VIN code.

Another issue for the V-8s is that the tag is riveted onto a removable part (generator bracket on Gen1, valve cover on Gen2/3). Easy to swap engine blocks or that part and lose the tag unless you make the effort to change it. The valve covers can also be swapped side to side, so if it's not on the passenger side front check the driver's side rear. Rarely are the tags fastened to an aftermarket cover, but I have seen one or two where the owner fastened the tag to the rear of one of the covers (could be either one). That's a good idea!!

The code is stamped on the block on the sixes and AMC/Jeep 2.5L fours.