In 1919, three years before the Avery Power Machinery Co. went bankrupt, a brochure discussed the company's engines. "The motor on the Avery tractors is of the valve-in-the-head type. Motors are built in three types: the T-head, the L-head and the valve-in-head. In the T-head motor (like Marv Stochl's 40-80 Avery), the valves are located on either side, with the result that the combustion chamber has two pockets, one on each side.
"In an L-head motor, the valves are arranged on one side, with one pocket or valve chamber. In the valve-in-head type, the valves are located directly above the cylinders. There are no side pockets or valve chambers."
Another feature of the Avery engine was its removable cylinder heads. "By removing the nuts from the stud bolts passing through the cylinder head, the head can be slipped off and the valves are so exposed that they can be readily ground."
The renewable inner cylinder wall was another feature far ahead of its time. The inner cylinder wall was cast separately from the main cylinder, which, according to the company, gave it several advantages:
"First, if you have any trouble, such as scoring from lack of lubrication or from any other cause, you can easily and quickly take out the inner cylinder wall and replace it with a new one at a very small cost. With the other tractor motors, should you have trouble of this kind, there is just one of two things to do - either take out the motor, crate it up and ship it back to the factory or to a machine shop and get it rebored, reground and have an oversized piston turned up and fitted for it, or throw it to one side and get a complete new cylinder.
"Either of these methods is a very expensive proposition, both in the amount of money it costs and in the amount of time you are without the use of your tractor, which might seriously delay your work.
"Second, all things wear out in time. When an Avery inner cylinder wall has become worn, you can remove and replace it with a new one yourself, at home or even right in the field, and your motor will be made new again.
"Third, the Avery's inner cylinder wall is cast separate and this enables us to use a harder metal which wears longer. You can also turn the cylinder wall part way around from time to time and thus equalize the wear on all sides.
"Fourth, if the water which you use for cooling contains sediment which collects on the inside of the cylinder, you can remove the Avery inner cylinder wall and clean the scale off by scraping it, and ensure the motor is being cooled perfectly at all times."