Prior to 1972, American car makers used the SAE (Society of Automotive Engineers) “gross” measurement of horsepower. Gross meant the figure was taken from an engine running on a dyno, with no air cleaner assembly, accessories or exhaust system connected.
By 1971, car makers began reducing compression in many engines in order to meet upcoming emissions requirements and to use unleaded fuel. General Motors and Chrysler began advertising both gross and SAE net figures in 1971, derived from an engine tested with air cleaner assembly, accessories or exhaust system connected.
The net ratings, which were applied across the board for 1972, must have been a shock to some customers. Suddenly, muscle cars appeared to lose 100 hp or more.For example, the Corvette’s optional LT-1 350 cu. in. small block V-8 had 370 gross hp in 1970 (with 11:1 compression), then a 330 hp gross rating (with 9:1 compression) for 1971-1972 with a 255 hp net rating. The mighty Chrysler 426 cu. in. Hemi kept its high compression and 425 hp gross rating for 1971 and showed 350 net hp.
Quote "People were stunned to see that an LS6 Chevelle SS, with 450-hp rating, put down 288 rear wheel hp in the dyno test. That would have put a net hp rating at around 350 hp for that big block." Quote HEMMINGS
Jester OUCH!!
Quote “Rear wheel horsepower was at least 30 percent lower than the reported gross figure, in some cases even more,”Quote HAGERTY (But now tests are done with a 12 to 15% figure)
Keep in mind that some muscle cars came specially prepped from press fleets and testing, sometimes with non-factory super tunes. That’s one reason that making comparisons using vintage Dyno & road tests from the factory can be different. Different axle ratios, testing methods, drivers, test conditions and other variables also affect results. NHRA ratings like the 1970 LT1 were done with cars that weren't modified' ( just Supertuned ) for the track And rated at 425 HP! NHRA didn't test cars off the show room floor LOL The factory did that!And any team running stock class super tuned their cars ( to max out performance of stock parts and settings like Timing, plug heat ranges, lighter visc. oil, Tire sizes, Carb jetting, loose lifter settings ETC 'ETC Same as we do on our Dyno tests on Muscle cars to get max performance While on a Dyno!!!!!
Don't tell me you guys put a car on a dyno and don't change the tune of the engine to make it better or do you get your 3 runs and just leave it alone get your graph and HP readings and leave:drunk:
! LOL
Quote "You don’t need a dynamometer to estimate net horsepower for classic muscle cars, or to check claims of current models. Roger Huntington, the renowned technical writer who penned articles for many car magazines into the 1980s, developed a formula to show the relationship between quarter-mile performance and power output. Others have refined those formulas and developed calculators, in which you can use performance figures and vehicle weight to get estimated hp. (To check hp figures for this article, we used calculators at http://www.stealth316.com/2-calc-hp-et-mph.htm.)" Quote
444 HP
QUOTE "Ford rates the modern BOSS with its DOHC 5.0-liter V-8 at 444 hp. Car & Driver, driving one the way most drivers would (not powershifting), recorded a 12.8-sec. ET at 113 mph. But Muscle "Mustangs & Fast Fords", with hot shoe Evan Smith banging off full-throttle powershifts and the car running on drag radials, scorched the quarter-mile in just 12.07 sec. at 114 mph." Those mph figures and the formula for figuring out HP from drag strip times gives you Different HP readings on the same car!!!!
The L72 tested to 450 hp at 6,400 rpm , but was changed to a rating of in the books and on record to 425 hp at 5,600 rpm at a point Lower on the rpm curve, these gross ratings were purely a fiction to satisfy insurance companies and the safety lobby!! That's why the early engines 427 FORD, 427 CHEVY, 426 HEMI, ETC ETC all came in at 425 HP in the books even though they made much more HP higher in the rpm curve!!!!
QUOTE "racing officials frequently “factored” underrated engines for the purposes of classification; Chrysler’s very strong 340 cu. in. (5,567 cc) engine, for example, carried a conservative 275 hp (205 kW) rating from the factory, but the NHRA treated it as a 325 hp (242 kW) engine for racing purposes." Quote
I Dynoed and helped crews tune these old engines at the time these factory ratings were present and from actual experience saw that these engines were under rated and produced much more HP at Higher RPMs then was advertized!!!! The 426 425 HP Hemi ran between 450 and 525hp on the dynos from engine to engine !!!! And the early LT1 was hovering around 400 some less some more! I know and others know but to convince anyone that refuses to except that is a like trying to tell someone that the Bible isn't all factual And if Snake bit enough times you DIE!!
I'll Continue later
LOL my typing finger has a blister
ain:
Jes
ain:er OUCH!