Can anyone tell me what is the difference between the A12 and the A12A

I can't tell you exactly what the differences are, but I can tell you that they are different and are a different casting.

The A12A can be rebored more than the A12 (be weary there is a couple of A12's too) with out falling into water/oil jackets e.t.c., not 100% but believe the A12A & A13 are very simular if not the same blocks.

I believe the engine mounts are in quite different position, as well as the distributor is place toward the centre of the block on an A12A compared to the front of the block (A12). By the way Brent, the engine out of the Sunny is an A12A...not an A12SA...probably not what you were after in the first place.

The difference in the A12's is the position of the dizzy.
The A12A has the dizzy underneath the #3 plug, same as the later A12.
I have an A12A and it appears to have the same mounts as the later A12 engine. Its only the first A12 (with the dizzy under #1 plug) that appears to have different mounts.

Converted, Its an A12A that I'm after ....
(not an A12SA)

Thanks guys.
The purpose of the question was to find out if it practical to use an A12 crankshaft in an A12A block for a cheap capacity gain

the A12 has a 73 mm. bore, the A12A has a 76mm. bore.
they use the same crankshaft which has a 70 mm. stroke.
the A12A has a block that is similar to the A13, A14, and A15 with the distributor between cylinders 3 and 4. the A12 has the distributor by cylinder 1. the A12A also has the revised oiling system like the larger A series.

My ACL catalogue shows the stroke of an A12A as 66.25mm. Is this true, because if it is and the cranks interchange, SpeedFreak might be able to mix and match to get some cheap cc's

My A12A has a 70mm stroke crank in it, not sure if its the original one or not and 78mm pistons giving me 1337cc - its a big block!

The A12A's has more cc at standard, I believe its because it has a bigger bore.

the a12a was produce from 79 to 82 the cranks stroke is the same but the a12a crank was stronger the con rods are same length the a12 rod uses a 17mm pin and a12a uses a 19mm pin the a12a block has 76mm bore increasing engine size to 1237cc the block also has the layout as a13 to a15 blocks for mount locations, distributer and oiling of the head.

I acquired a 1984 Nissan Competition Parts catalog at Shasta. Here's what it has on the A12A:

Block:

11010-H2300 A12 BARE BLOCK 73mm/2.87" bore size
11010-H9660 A12A BARE BLOCK 75mm/2.95" bore size
11010-H6200 A13 BARE BLOCK 73mm/2.87" bore size
11010-H9700 A14/A15 BARE BLOCK 76mm/2.99" bore size

So the A12 & A13 share the same bore size. The A14 and A15 likewise share 76mm. The A12A is unique.

Pistons for the A12/A13 (same piston) come in 73, 73.5, and 74mm oversizes. The latter is 0.040" over
Competition Pistons for the A12A/A14 (same piston) come in 76mm. For the A14 only they listed 76.75 and 77mm pistons.

Cranks:
12200-H8515 A12/A12A CRANKSHAFT 70mm/2.76" stroke
12200-H5720 A12 COMPETITION CRANKSHAFT 70mm/2.76" stroke
12200-H8915 A13/A14 CRANKSHAFT 77mm/3.03" stroke
12200-G3400 A15 CRANKSHAFT 82mm/3.23" stroke

Connecting Rods:
12100-H1000 A12 CONNECTING ROD 121.5mm/4.78" center-to-center
12100-H8500 A12A CONNECTING ROD 121.5mm/4.78" center-to-center
12100-H6200 A13 CONNECTING ROD 133mm/5.24" center-to-center
12100-H7200 A14/A15 CONNECTING ROD 133mm/5.24" center-to-center

> The purpose of the question was to find out if it practical to use an A12 crankshaft in an A12A block for a cheap capacity gain

Why not just use the A12A block and the A12A crankshaft for 1237cc? That will definitely work. But the A12A engine block is hard to find anymore, since it was only made in 1979-1982.

Keep in mind that 1971-1973 A12 and 1973-up A12 are the same (1171 cc) but the distributor location and motor mounts changed. We didn't get this newer A12 in the USA.