My father said that the R2800 was considered efficent because it put out 1 hp for every pound that it weighed ( up to 2500hp and weighed 2500lbs ) The carb. for that engine weighed 75lbs and I can just about stick my thumb in the jets. It burns about 100gl an hr at cruise. The radial only has 1 set of main bearings per row of cylinders. Radial engines have a master rod that all of the other connecting rods join on to.