The "500" number is "SAE Net" ie at the flyweel with accesories (more like 493). Wayne is sharing his 2WD "Wheel" Horsepower ie normal 4WD HP was naturally even lower - I think 366 was stated.

Here is what I wrote when HP came up on another board.

-mick

What's the difference (is there a difference) when people say "brake horsepower" and just "horsepower"?


Horsepower is the amount of work done over time. Lifting 33,000 pounds one foot over a period of one minute is working at one horsepower.

Automotive prefixes like "Brake", "SAE Gross", "SAE net" and "Wheel" offer clues as to how or under what conditions the horsepower is measured. Note that torque is what is normally directly measured by applying resistance to the engine - horsepower is then computed as Torque x RPM / 5252.

"Brake" and "SAE Gross" implied measuring horsepower at the flyweel with all engine accessories removed.

"SAE Net" (the most commmon US Auto HP rating and used since 1972) is also measured at the flywheel but with all the accessories hooked up.

"Wheel" is normally measure on a rolling dynamometer and thus takes into account losses in transmissions etc.