After being excluded from his first ride, he showed his class by eventually finishing 3rd with 11 points after defeating future triple World Champion Erik Gundersen in a runoff.
Sigalos joined Ipswich Witches from Hull Vikings in 1981 after a record £35,000 deal which included fellow American John Cook.
He made his second and last World Final in 1983 in West Germany, but struggled on the day and finished in 8th place having scored 8 points.
Sigalos became World Pairs Champion with Bobby Schwartz in November 1982 at the Liverpool City Raceway in Sydney, Australia.
His partner and team captain "Boogaloo" Bobby Schwartz proved his worth by finishing second to Sigalos in each of their six heats.
By finishing the Final undefeated, and with the ending of the World Pairs Championship after 1993, Sigalos remains one of only three riders to achieve the feat, the others being Ivan Mauger in 1969 and Ole Olsen who did it in 1973 and 1975.
He was runner up in the AMA National Speedway Championship in 1981 and 1982 and finished second and third for the United States in the 1980 and 1983 World Team Cups.