2006 build date
#11
03-27-2005 | 02:29 AM
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Joined: Jan 2005
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RE: 2006 build date
Re: horsepower
Back in the early ’70s, horsepower ratings fell through the basement seemingly overnight. Ever wonder why? There were several factors involved, including reductions in compression ratios on all engines (some so small it’s hardly worth mentioning, others considerable), and ratings taken at different rpm than previous years. However, the biggest reason for the dramatic changes was that starting in 1972 auto manufacturers adopted a “net” system of rating engine power, as opposed to the “gross” figures they had published in years past.
Simply put, the gross rating system was a measurement of an engine’s power, at the flywheel, taken without any restrictions on the engine’s ability to perform. Engines were set up on a dyno and the measurements were taken with no air cleaners in place, no alternator or other engine-driven accessories, and very often with tubular headers. Mufflers? No way! That changed in ’72, partly in an effort to “under rate” a car’s performance capability and mollify the insurance industry, and partly to give a fairer “real world” estimate of what kind of power buyers could expect from their car. Net horsepower ratings were taken with all the crank-driven accessories in place, a functioning air cleaner, and factory exhaust manifolds. As an example of what the new ratings did to advertised engine performance, the gross horsepower rating for a ’71 383 4bbl engine, with 8.5:1 compression, was 300hp at 4800 rpm. Its net rating was 250.
So when the venerable 426 Street Hemi was rated at 425hp, it was impressive. When the Viper came out and was rated at 400 horses, we all “ooo-ed” and “ahhh-ed” over it because it was the most powerful engine to come out of Detroit in over 20 years. But it still didn’t have the numbers of the Hemi. Or so we thought. In fact, it was more impressive, because that 400 horses was a net power rating, compared to the Hemi’s 425 horse gross rating! When the Viper V-10’s ratings got upped to 450 a couple of years later, the raw numbers showed an engine that had finally surpassed the published ratings of the legendary Elephant.
Back in the early ’70s, horsepower ratings fell through the basement seemingly overnight. Ever wonder why? There were several factors involved, including reductions in compression ratios on all engines (some so small it’s hardly worth mentioning, others considerable), and ratings taken at different rpm than previous years. However, the biggest reason for the dramatic changes was that starting in 1972 auto manufacturers adopted a “net” system of rating engine power, as opposed to the “gross” figures they had published in years past.
Simply put, the gross rating system was a measurement of an engine’s power, at the flywheel, taken without any restrictions on the engine’s ability to perform. Engines were set up on a dyno and the measurements were taken with no air cleaners in place, no alternator or other engine-driven accessories, and very often with tubular headers. Mufflers? No way! That changed in ’72, partly in an effort to “under rate” a car’s performance capability and mollify the insurance industry, and partly to give a fairer “real world” estimate of what kind of power buyers could expect from their car. Net horsepower ratings were taken with all the crank-driven accessories in place, a functioning air cleaner, and factory exhaust manifolds. As an example of what the new ratings did to advertised engine performance, the gross horsepower rating for a ’71 383 4bbl engine, with 8.5:1 compression, was 300hp at 4800 rpm. Its net rating was 250.
So when the venerable 426 Street Hemi was rated at 425hp, it was impressive. When the Viper came out and was rated at 400 horses, we all “ooo-ed” and “ahhh-ed” over it because it was the most powerful engine to come out of Detroit in over 20 years. But it still didn’t have the numbers of the Hemi. Or so we thought. In fact, it was more impressive, because that 400 horses was a net power rating, compared to the Hemi’s 425 horse gross rating! When the Viper V-10’s ratings got upped to 450 a couple of years later, the raw numbers showed an engine that had finally surpassed the published ratings of the legendary Elephant.
