Oxford Plains Speedway and Beech Ridge Speedway were Si’s "home" tracks for most of the 1950’s. In 1952, he won the opening day race at Beech Ridge – the beginning of a dominating year where Si won his first track championship. And, he was just as dominating at his other "home" track where he won back to back track championships at Oxford in 1953 and 1954.

In the early 1950’s, Si frequently raced on dirt tracks in Quebec until the track promoters told him to stay away because he won too much.

Si moved to Massachusetts in the late 1950’s where he built winning race cars for others as well as himself, winning races at the old Peabody (MA) Speedway and Norwood (MA) Arena.

He returned to Maine following his retirement as a race driver in the early 1960’s. Si Parlin used his wealth of racing experience and mechanical skills to help many local racers.