I know there is a way to tell the 312 from other Y blocks at a glance. I read a posting somewhere that told how, but I can't remember. Anyone remember the mark or casting to look for?
www.ford-y-block.com/Block%20identification.htm Here is where you can get your information.
Looks like it is hard to tell the 312. Here is another way, but not the easiest. Since 312s were machined from the same block casting as a 292, they are nearly impossible to identify externally. Any casting number used on 312 blocks was also used on 292 blocks. Although most 312s were ECZ5015 followed by A, B or C, these can also be a 292. The best way to identify a 312 externally is by checking the flywheel flange on the crankshaft. The 312 ECZ crankshaft has an aspirin-sized dot on the outer edge. If the engine is disassembled, check the casting number on the main cap. ECZ is cast into 312 main caps; all others are EBU.
2X like Clusterbuster stated. Any other way is just very misleading.
The crankshaft dot was what I was trying to remember. Thanks ...I will write it down this time.