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The Delta 490 (displacement 4.9cc, not .49 cuin) was introduced to the Australian scene in mid 1952. The engine was designed and built by South Australian engineer, Allan McCollouch for the somewhat legendary, or natorious, W Wilton (Bill) Evans. The engine was Evan's answer to the English Frog 500 and local Sabre .29 recently introduced by Gordon Burford.The first engines were twin ball race, reear rotary valve. To reduce cost, the ball races were soon dropped. Final versions were plain bearing, front rotary induction.
The engine was produced in small numbers for about 15 months with production totaling no more than a few hundred units. All featured 360° porting, ED style, produced to varying standards with the "good ones" being very good indeed. The plain bearing RRV engines used the same crankcase, but had "cooling fins" turned onto the exterior of the front race housing to turn it into a feature. Engines with plain and finned heads have appeared (see photos), as well as two and three bolt backplates with straight and bell-mouth venturis.
Although Evans announced other models, the 490 RRV and FRV were the only ones made. Bill Evans turned his interest to speedway racing, although he maintained some interest in model engines as the Australian Enya agent. McColloch, who was also responsible for Evans' Gee Bee Red Special, appears to have had no further involvement with model engines.