The 1971 spec chart shows 340 gross / 270 net (as-installed) for the base 442 455. The chart didn't specify a difference in rating due to transmissions. However, in 1972 - with minimal changes to the drivetrain - the ratings were 250 net for the automatic and 270 net for 4 speed cars with the hotter cam and big valve heads.

The 1970 base 455 was rated at 365 gross, so a 25 gross hp difference between and 1970 and 1971 if the ratings were accurate.

Terry

 

The 1970 horsepower figures were underestimated according to others. I just was wondering how accurate the 1971 ratings were relative to the rear wheel dyno numbers?
thanks
joepenoso

 

From what ive seen, with GM's underestimations in power, the rear wheel horsepower usually matches up with their advertised horsepower (since there will be a drop from crank to rear wheel but that drop is made up for by the fact that the crank is actually putting out more power than advertised, essentially making up for that estimated 20% loss) with that in mind the net horsepower would most likely be extremely close to the true rear wheel horsepower.

Most likely 270 rear wheel horsepower for a stock 71' 4-speed and 250 rear wheel horsepower for a stock 71' auto. Then you can add vette442's 25hp estimate to that to get the 70' model estimates. But then again, as i always say, in the world of Olds whats horsepower? just a fancy number on a piece of paper. Torque is where its at

 

I gotto agree. I am new to Oldsmobile and previously owned a new 1977 4 speed, 3.23 Firebird formula 400/220horse. I wondered if the 71 455 auto Olds had more than 200 RWHPstock. I just got it and haven\t driven it yet for any distance.
joepenoso