AY12 engine

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The AY12 is so rare it has been dubbed the Nissan Mystery Motor. It was used in works Datsun Cherry racing cars.

Overview

Cross-flow Double-Ignition AY12 OHV 160ps @ 8,800 rpm

A12 cross flow engine in a Cherry X1-R raced in the Fuji speedway Victory 200 race in 1973.

It is rare as. Probably the rarest Datsun engine of all. Almost no one has ever seen one, but they exist in photos and old magazines.

Nissan Part Number 11041-M0820. See the FIA homologation papers for the PE10/A12GX E10 Datsun Cherry.

LTR was planning to create a new head casting: Remake of the Crossflow.

It used a large right-angle distributor lying horizontally along the block. It served eight spark plugs, so these engines used two plugs per cylinder. The original design & prototype head used only one plug per cylinder but the racing heads used two.

Benefits

Using a stock A12 engine block, here are some benefits of the racing-only A12Y cylinder hear:

1. It is crossflow, the inlet and exhaust are on opposite sides of the head.
2. Using a hemi cylinder head design, the valves are in better position than in the normal model. Racing trim was reportedly 220 gross horespower
3. The is no heat problem with twin carbs, because they are on diffent side than the exhaust manifold.
4. The chamber is hemi, it can take more compression without unintended pre-detonation (knocking or pinking/pinging)
5. The exhaust side is the same as normal head. The ports are not in same place but one can use standard A12GX exhaust manifold

Documentation

Full-page article on the AY12 in Auto Technic Magazine 1982 volume 14 no.164.

Bottom: AZ12 DOHC Engine similar to the Nissan LZ Engine

This is just a diagram. It seems no AZ12 was actually produced.

Oil Pump with upright filter boss for Cherry FF (FWD) race car

Swap Notes

1. In a right drive, rear drive car, the rear carb is likely to cause interference problems with the brake cylinder. Solution: use a remote brake master cylinder.
   • Left side drivers, however will immediately see the advantages
2. The exhaust can quite obviously be made in a more conventional style to allow a lot more room in there
3. The induction on this one precludes the use of a conventional distributor
   • One could use a right angle drive to lay the distributor down alongside the block, but it makes it hard to service.

     

   • Or use an EDIS crank trigger ignition
4. In RHD, the carbs in the picture are causing a problem with the routing of the clutch cable. Again, LHD cars will have no problem

The head was originally designed for a transversely mounted engine in the Cherry range of cars & some of the clearance problems simply did not arise because of this transverse mounting.

The cure for some of these problems might just be a custom EFI induction with a crank angle sensor made from a modified distributor & let the computor sort out the spark problem. Even a simple Pertronix conversion would very likely serve this purpose quite well for many aftermarket computers. Just make a flat[ish] cover for the distributor to replace the distributor cap, & run two coils in a wasted spark configuration.