Mainly when I refer to an older design, it has more to do with materials, and how they are applied. And to some extent the manufacturing capability as it was - as oppose to what is now available to hold tigher tolerances, cut intricate shapes and such. The basic knowledge of what an engine is, how to design one, and optimize it has been around for a number of years. Dub will be the first to tell you he learned a great deal from guys like Duke Fox.

Also, remember that mufflers were an oddity back in the 60s and early 70s. Some engines, and their carbs, were developed to run open exhaust, with the use of an exhaust baffle to aid in idle performance. Carbs tende to be small, tight venturi's were helpful- no muffler pressure to help out So as time went on, some of the designs were tweeked to incorporate a muffler, but sometimes they didnt do much to change the carb. So I guess you could consider these 'transitional' engines as older designs. A good example here is a ST G-60 with PDP porting. As time went on, many developed into real nice power plants.

The Kraft 61 was one of the first steps at building a good, schnurle ported engine, designed for a muffler or pipe, from the ground up. The Webra Speed .61 and original Rossi 60 were huge leaps in performance as well.

At the moment, Jett does not make a .61 (10cc) full size engine. The larger 'big block' engines are .76 up to the 1.20 (Dub at one time did build a few big block .61 engines as special order). However, Jett does make the 60L engines. These are "40" size engines. Can be set up for either speed, or torque, or something in between, depending on how you wish to use one. A standard SJ-60L with the jett-stream muffler would be ideal for most larger .40 size sport planes, and for smaller pattern planes. For example, some of the older designs like the Phx 5 and Intruder that once used the ST53 engine are ideal applications for an engine like this. Even with an un-tuned muffler, the engine puts out great power for its size.

The Jett engines are sold direct only. Its the only way found so far to provide the best product support and service. Dub knows who bought the engine, and many of the engines are configured for special applications. Not quite custom built, but they are assembled to order.