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horsepower ratings, new v.old

This is a discussion on horsepower ratings, new v.old within the Firebird / WS6 forums, part of the Vehicle Specific category; I am curious on how horsepower ratings have changed from say a 1969 Chevelle with 375hp to a 2001 T/A ...

  1. #1
    Junior Member
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    Apr 2007


    Question horsepower ratings, new v.old

    I am curious on how horsepower ratings have changed from say a 1969 Chevelle with 375hp to a 2001 T/A with 325 hp. Aren't they figured differently now than they used to be? Also, how would you compare the old muscle cars with the new ones in the ratings? Just curious!

  2. #2
    Join Date
    Mar 2007

    2000 Trans Am

    First of all the ls1 makes 350hp and 355trque, now the chevelle that made that much power also had a bigger motor and those cars back then were heavier, a full wieght chevelle with that much power is in the 14s a ls1 car with 25less hp is mid to low 13s.

  3. #3
    Member SAGGIN's Avatar
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    May 2007
    Elk Grove, CA

    02 SS, 03 BMW 745

    I don't think rating really apply becasue our cars are pony cars and back then they were muscle cars and you can't really just compare the care based on numbers or ratings. Thats what I think IMHO.

  4. #4
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    mrr23's Avatar
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    Jul 2005
    orlando, fl

    2014 camaro 2ss/rs

    originally, motors were rated with no accessories attached to the motor on the dynos. it was called gross ratings. as the years passed, they started dynoing them with the accessories on them. they call that net ratings.
    Cold Air Intake, Muffler Delete, Vinci High Performance Dual Valve Springs, Hardened Pushrods, Yella Terra 1.85 Rockers, Some Hydropdipped Stuff, Strut Tower Brace, Some SS Badges, boost/vacuum gauge, fuel pressure gauge

  5. #5
    Firebird Encyclopedia 9T8W66's Avatar
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    Oct 2006
    St. Clair Shores. Michigan

    Navy Blue Metallic
    `98 Formula M6 HdTp

    Yeah Pre `71 Cars all recieved a gross rating post `71 cars recieved the net rating. Although the factory ratings were sometimes underated for Insurance reasons The `71 455 HO Engine in the Trans Am and GTO's was rated 335 HP Gross and 310 HP Net and was the top performance engine in `71 This is also the year all GM cars went to unleaded gas and compression ratio's dropped.
    The previous year the 400 Ram Air IV was rated at 370 HP gross but actually made over 400 HP
    Weight isn't a factor as much as you might think. A Chevelle GTO or 442's average weight was about 3600 lbs.
    I raced a Buddy with an original `69 GTO Judge, Car was equipped with 400 Ram Air III [366 HP], M21 4spd and 3.90's Only changes on that car was a Super tune and modern radials and it would run door to door with my LS1.
    If he got out ahead I had a hell of a time trying to catch him so the cars were pretty even in power.
    Semi Retired Street Racer
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  6. #6
    Junior Member
    Join Date
    Apr 2007


    makes some sense now. thanks

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