old hp vs. new hp Hope someone can help. I understand that in the early 70's they changed the way that horsepower was rated. How does that compare to the new way? For instance, a 1966 Buick 310 Wildcat has 220 hp. A 1980 Olds 350 has 170 hp. They were tested differently. If they were both tested the old way, would the newer motor have more hp than the 170 it's rated at today? If so, how much? How are these hp's calculated? Thanks for any help. By the way, I love this web site. It is soooo informative. Jim
Hello Jim, I read this little story a few months ago and decided to copy it and store it in a WORD document, useful info that I keep on copying and copying "In 1971, the entire American automobile industry changed the way it rated horsepower. The older system, called brake or gross horsepower, was measured without a transmision attached to the engine. The engine ran open exhaust and was free of power-robbing accessories. The brake horsepower technique did not even require the engine to run it's own waterpump let alone a alternator, airpump or power-steeringpump. In 1971, the Society of Automotive Engineers (SAE) method for measuring net horsepower was adopted. Following SAE procedure J245, the engine was now required to run the test with all power accessoires, muffled exhaust and the transmission and torque converter in place. The combination of lower power from less compression and a different way to rate power was a shock to car enthusiast throughout America. The big, bad 454 Chevy (sorry about this, was just in the text ) that used to carry a 390 brake horsepower rating, now had a 285 net horsepower label. This can be read as more than a 100 hp loss, unless you are careful and knowledgeable. Likewise, the 300 bhp version of the 350 with fourbarrel carb was now packing at just 175 net hp.''
