1973 Pontiac Firebird Formula 455-SD

[Stan Weiss]

Originally Posted by Travis Miller

Refactoring of engine horsepower by NHRA actually started as early as the 60's but it was kept a secret for whatever reason until they published a book called the "Factor Finder" in 1972 followed by an updated version in 1973. Sometime in 1973 is also when NHRA started listing the refactored horsepowers at the bottom of the column in the classguide.

What engine combo are you trying to find out the date when it was refactored?

Stan