Quote:
Originally Posted by Harley Eaton
According to the Official Ford Parts book 1949-1959, all Ford passenger cars and Thunderbird, 1952 thru 1957 with 239, 272, 292, 312 engines use C0AZ-6564-A rocker arms.
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Not true. First of all, 52 and 53 did not have rocker arms - the engines were a flathead. There were two rocker arm ratios used over the years. The 57's and 58's used the high ratio rocker arms, the rest of the years used the other one as far as I know. They also had two different styles for adjustment as the writer has noted.
The COAZ came out in 1960 and is probably a replacement. All replacement were the lower ratio rocker.