THE D.O.H.C., PARALLEL-TWIN Porcupine first appeared in 1947. The nickname derived from the quill-like cylinder head finning between the twin cam boxes, although this feature had been deleted by 1954. Initial plans to cast the cylinder heads in silver for good thermal conductivity were abandoned due to cost.
It should have had a supercharged engine, but the postwar ban on superchargers prevented this. Fed by twin carburetors with a single, remote-float chamber, the engine never realized its potential.
| Model: | AJS Porcupine |
| Capacity: | 500 cc |
| Power output: | 80 bhp (7600 rpm) |
| Weight: | 143 lb (65 kg) |
| Top speed: | Not known |
| Country of origin: | UK |