'72 455?

[scott303]

I was looking up the engine stats on a 1972 oldsmobile 455 and it gets 270 horsepower, where as in prior years they got 370,although these were w-30's. I was just wondering why the significant horsepower loss? is the 1972 a two barrel?

[MagicRat]

Originally Posted by scott303

I was looking up the engine stats on a 1972 oldsmobile 455 and it gets 270 horsepower, where as in prior years they got 370,although these were w-30's. I was just wondering why the significant horsepower loss? is the 1972 a two barrel?

Most of the power loss was due to the way horsepower was measured.
A change in this measurement was made for the 1971 model year, so the HP numbers dropped (approx. 30%) compared with 1970 and previous years, even if the actual power output was the same.

This change applied to all auto manufacturers selling cars in the US, not just GM.

Government standards stated that for 1971 and later power had to be measured with the engine equipped exactly as if it was in the car, including stock air cleaners, exhaust, water pump, PS pump and all emissions controls installed and working.

In previous years, manufacturers had much more freedom to tune engines for max power and to leave power-robbing components off during their testing.

Also, prior so 1971, lots of power ratings were changed for advertising or marketing reasons, either to increase HP for more impressive numbers in the advertisements, or reduce the numbers to mislead the insurance companies.

Finally, there was somel real power loss in 1971 and 1972 (depending on the manufacturer) compared to 1970 as engines received lower compression ratios so they could use unleaded fuel.