One of my own all-time favorite model diesels! Introduced in early 1959, the FROG 349 was designed by George Fletcher. With its rear drum valve induction, cross-flow loop scavenging and single ball-race crankshaft (a plain bearing version was also available), it broke new ground in the context of British model diesel design.
The FROG 349 was manufactured initially by International Model Aircraft (IMA) and later by Davies-Charlton (D-C) Ltd., surviving in the marketplace until 1966, when all FROG production was terminated. This well-made and powerful engine is a most dependable motor for use in mid-sized control-line models and large sport free-flight applications. In its standard production form, it did not achieve its full performance potential, mainly due to manufacturing cost considerations. A little knowledgeable tuning realizes much of that potential, turning the FROG 349 into a very sprightly performer indeed by the standards of its day.
The full story of the FROG 349 may be found on Ron Chernich's "Model Engine News" (MEN) web-site.