Petter PAZ1 Diesel Engines

Petter PAZ1

The British built Petter diesel is a storied brand but not well known here in the U.S. The Petter began in 1892 when twin brothers Ernest and Percy Petter grew up enough to branch the family foundry business off into the engine business. After a short foray into high speed steam engines, the duo began working on internal combustion engine designs and eventually developed 1-2.5 horsepower horizontal hot bulb oil engines which would eventually result in the Petter PAZ1. They are also reported to have built England’s first internal combustion-powered motor car in 1895.

In 1901, the Petter brothers then set up a branch of their father James Petter’s business and began producing a more advance line of oil engines from 1.25 to 22 horsepower. About the time James Petter died in 1910, the company had reorganized as Petter Ltd, a public company. Responding to an influx of Fairbanks-Morse engines from the U.S., Petter designed a new TVO (Tractor Vaporizing Oil, aka: kerosene mixed with gasoline) engine called the “Handyman” that was both inexpensive and effective. This set the company on an upward trajectory in both oil and gasoline engines and later diesels.

After the Petter Brothers had died in 1955, it soon became apparent that Petter was going to be bought by a larger company. That turned out to be Hawker-Siddeley (most famous for making aircraft) in 1957, and they reorganized Petter into several divisions. Hawker-Siddeley would also buy another small diesel manufacturer, Lister, in 1986, a company that competed with Petter in the small diesel market, and merge the two into Lister-Petter, a company that remains in business, though with new corporate owners.

As it relates to the engine we are covering here, we’ll jump ahead to when Petter began production of the A-Series powerplants in 1936, which were 1-cylinder air cooled gasoline… petrol in Britspeak… engines. The A engines came in various configurations, outputs and updates over that time. The ‘45-51 A1 engine became the base architecture for a diesel variant that debuted in 1953 as the PAZ1.

The PAZ1 was a cast iron, direct injected, single cylinder, air-cooled diesel that weighed in at about 240 pounds dry, more or less depending on configuration. It was a square engine, with a 3 x 3 inch bore and stroke. Rated output remained largely the same throughout the production run, a maximum of 3 horsepower at 1800 rpm. The engine could also be configured to run at 1000 rpm, at which it produced 1.5 horsepower. When set to 1500 rpm, it produced 2.5 horses. A peak torque value of 11 lbs-ft occurred at 1500 rpm, at which the best fuel consumption was attained, about 0.2 gallon per hour with a full load.

The PAZ1 was designed to operate small equipment. Rarely, it was used to power watercraft or land vehicles. It became famous and common in England for powering small cement mixers. The engine is collected in the UK and it would seem the vast majority of the restored engines came from cement mixers. They also saw extensive use powering pumps. To a lesser extent they powered generators.

Starting in 1963, the first major revisions came. Dubbed the Series 2, they feature a redesign of the cooling system, improvements to the governor, changes to the fuel system and updates to the decompression system. We are told there were other revisions later but could not find any comprehensive lists of what was done.

Some sources list the end of PAZ1 production at 1979 and others at 1981. One source listed almost 100,000 engines produced. Petter also had an extensive line of other engines throughout it’s history, so it was a big-time producer of small engines. While the Petter line had become somewhat “technically stodgy” prior to Hawker-Siddeley acquiring the company in ‘57, that event triggered a bevy of newer and more modern designs. Many of the older Petter engines faded away early in that process but the PAZ1 soldiered on later than most of the old timers in the lineup.

Sources

Hercano Propulsion
740.745.1475
herculesparts.com