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Old August 28th, 2009, 11:56 AM   #1
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What are the real hp and torque ratings of 455 motors?

Are the horsepower ratings true or not? The older 455 ratings seem right but did they rate the newer ones(72-76) @3000 rpm? What were the actual ratings @ 5000 rpm?
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Old August 28th, 2009, 06:35 PM   #2
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Most of the engines were purposely rated below the actual hp and torque to ensure they could meet the stated rating posted for them.
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Old August 28th, 2009, 09:02 PM   #3
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Wasn't it from '71 on that they started rating them in net HP? As opposed to gross HP.
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Old August 29th, 2009, 02:19 AM   #4
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They differ from car to car but will be in the stated ratings. They truly mean nothing as the only measurement that counts is how many you are putting on the road and can only get rear wheel hp and torque from a dyno.
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Old August 29th, 2009, 02:27 AM   #5
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http://www.442.com/oldsfaq/ofeng.htm#ENG 1964 - 1990 Engine Performance does not say when there system was changed.
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Old August 29th, 2009, 05:29 AM   #6
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If you do the math. My 68 W30 was rated at 360 HP it ran a 13.9@97MPH on a perfect day, it's closer to 325 HP. If a 70 98 Olds had 365 HP it should run in the low 14's, they might run a mid 15 sec 1/4 mile at best.
Some motors were closer than others.
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Old August 29th, 2009, 09:00 AM   #7
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The 98 was alot heavier tho wasn't it. Did they rate them @ 3000 RPM because of insurance in the 70's?

Last edited by nickd; August 29th, 2009 at 09:04 AM.
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Old August 29th, 2009, 09:10 AM   #8
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It was 1972 when they changed the way horsepower was rated. If I remember correctly, it was rated off the back of the transmission with a closed air cleaner and exhaust.
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Old August 29th, 2009, 09:49 AM   #9
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According to the article in the link below the early "gross" ratings were taken with a basically bare engine with open headers and optimized timing. The later "net" ratings were acquired with all the accessories and exhaust in place, stock ignition timing. Both were taken at the flywheel with the engine on a test stand.
The HP numbers weren't written in stone, that's for sure. Just about whatever they needed them to do they did.

http://ateupwithmotor.com/terms-and-...orsepower.html
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Old August 29th, 2009, 09:53 AM   #10
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68-76 Olds 455 HP rating: Not enough.
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Old August 29th, 2009, 10:27 AM   #11
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Is there such a thing as to much hp. Me thinks not
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Old August 29th, 2009, 10:27 AM
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