My girl friend has a 1982 tercel. I planning on getting it running and need to know which engine is in it.
I imagine I can use the VIN number to find out if it has a 3AC or 3A engine int it.

Does anyone know what the difference is between these two engines?

My guess it that the "C" stands for the engine that was manufactured to meet California standards. My 81 has a 3A-C and it says it right on the valve cover..... Here is a link to a site that has a pic of the 3A

http://en.wikipedia.org/wiki/Toyota_A_engine

The 1.5 L (1452 cc) 3A was produced from 1979 through 1988. Cylinder bore was 77.5 mm (3.05 in) and stroke was 77 mm (3.3 in). It was a 2-valve SOHC like the 1A and 2A. There were California-spec (3A-C), Japan-spec (3A-U), transverse (3A-L), and swirl-intake (3A-S) versions of the same basic design.

Power output ranged from just 62 hp (46 kW) at 4800 rpm all the way to 90 hp (67 kW) at 6000 rpm. Torque was less spread from 75 ft·lbf (101 N·m) at 2800 rpm to 89 ft·lbf (120 N·m) at 4000 rpm.