Seddon artic the Perkins badge was always a giveaway, and engine is probably a P6 or Land Rover built their own diesels of course, but a few, like this 109 Series II, were converted to Perkins 203 or Another interesting research department project was the Duplex. Thought up by research head Philip Jones, this was a supercharged two-stroke, using a split single-cylinder and a Roots-type blower for scavenging. The prototype had a special curved con-rod which was developed by Perkins new stress garage door opener grinding noise laboratory, while the DPA pump was modified to give two injections per engine revolution. The test engine was smooth and quiet, but smoked a lot and had poor economy.
It was, according to ex-Perkins employee and author David Boulton, a useful learning experience. Some engine problems, however exacting the lab work and however many thousands of test miles were built up, only came to light when customers were out on the road. This happened to the 354 turbo in the US, and it was down to road design. When coming off the freeway down a slip road then rare in the UK , drivers would change down early to maximise engine braking, something their traditional garage door opener grinding noise V8s had borne without a problem. But this could seriously over-rev the 354, which had the standard British over-speed allowance of 30%.
The result was a flush of warranty garage door opener grinding noise as the valve gear failed. Shorter, stiffer valve springs and modular iron rocker levers gave a safe limit of 4200rpm and solved the problem. The 354 might be the backbone of the range, but Perkins needed a four-cylinder diesel as well, for smaller trucks and tractors. This was the 236, launched in 1965 and effectively a four-pot version of the 354, though with balance shafts to reduce vibration. Like its big brother, it could suffer from high oil consumption, thanks to the block changing shape after many miles of running distorting the bores.