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<blockquote data-quote="71ProjectJunk" data-source="post: 409862" data-attributes="member: 7655"><p>Yes, the horsepower rating went from "gross" to "net" in 1972. So, the 240 HP gross engine went down to 164 net because of the lower compression in 1972 and mostly because of the change in how HP was measured. In 1971 some manufacturers rated their engines in both net and gross hp. Just the change in how engines HP was measured easily took out 20-25% of the advertised power. Net HP measures the engine as it is run in the car with manifolds, full exhaust, all emission equipment, alternator, water pump, PS, AC, engine fan, air cleaner, everything as the engine runs in the car. Gross HP is how HP is usually measure on your local dyno room, engine with no accessories, water pump run by an electric motor, no emission, no air cleaner, no exhaust. There is a huge difference in power when you have no accessories, air cleaners, exhaust etc... </p><p></p><p>As for wheel HP like Superbond measured on his car at 214 HP. Wheel HP is even lower than net HP, because that takes into account ALL parasitic loses including the transmission, and rear end. No manufacturer has ever used rear wheel horsepower to rate their engines. Rear wheel HP on an automatic transmission car will be anywhere from 15-20% less than what net HP is. On a Mustang with an automatic transmission and a 9" rear end you are looking at closer to the 20% mark. So, that 351 which made 214 HP at the wheels, probably was making close to 260 HP at the flywheel (net HP as all engine accessories and exhaust are hooked up), and easily 330-350 Gross HP as HP was measure in the muscle car era. To put that into perspective, in 1971 Chrysler rated all their engines in net and gross HP. The 426 Hemi was rated at 425 gross and 350 net HP, that is a 75 HP drop in just how the engine HP is measured. Chevrolet did the same thing the 1971 350 LT1 was rated at 330 gross HP and 255 net HP, that is a drop of 75 HP, just on the way HP was measured.</p></blockquote><p></p>
[QUOTE="71ProjectJunk, post: 409862, member: 7655"] Yes, the horsepower rating went from "gross" to "net" in 1972. So, the 240 HP gross engine went down to 164 net because of the lower compression in 1972 and mostly because of the change in how HP was measured. In 1971 some manufacturers rated their engines in both net and gross hp. Just the change in how engines HP was measured easily took out 20-25% of the advertised power. Net HP measures the engine as it is run in the car with manifolds, full exhaust, all emission equipment, alternator, water pump, PS, AC, engine fan, air cleaner, everything as the engine runs in the car. Gross HP is how HP is usually measure on your local dyno room, engine with no accessories, water pump run by an electric motor, no emission, no air cleaner, no exhaust. There is a huge difference in power when you have no accessories, air cleaners, exhaust etc... As for wheel HP like Superbond measured on his car at 214 HP. Wheel HP is even lower than net HP, because that takes into account ALL parasitic loses including the transmission, and rear end. No manufacturer has ever used rear wheel horsepower to rate their engines. Rear wheel HP on an automatic transmission car will be anywhere from 15-20% less than what net HP is. On a Mustang with an automatic transmission and a 9" rear end you are looking at closer to the 20% mark. So, that 351 which made 214 HP at the wheels, probably was making close to 260 HP at the flywheel (net HP as all engine accessories and exhaust are hooked up), and easily 330-350 Gross HP as HP was measure in the muscle car era. To put that into perspective, in 1971 Chrysler rated all their engines in net and gross HP. The 426 Hemi was rated at 425 gross and 350 net HP, that is a 75 HP drop in just how the engine HP is measured. Chevrolet did the same thing the 1971 350 LT1 was rated at 330 gross HP and 255 net HP, that is a drop of 75 HP, just on the way HP was measured. [/QUOTE]
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