[uneasyrider]

In 1972 SAE net hp was rated at the tail shaft of the transmission with the AC and any other option (including the alt.) turned on. It was averaged between 4spd and auto. cars. This gave a “more realistic� hp rating than the gross hp ratings of the muscle car era. Before SAE net they would measure the hp at the flywheel with out even a water pump or alternator attached to the engine and “open� exhaust a lot of times. The problem with SAE net is that they never set stringent enough guidelines on exactly how to measure it so it has been “doctored� many times in the resent past to give falsely higher hp claims. The Ford Mustang is a good example of that. A few years ago they were caught “doctoring� their advertised hp and rating it several hp higher than it was to compete with Chevy’s Z28. As a rough figure you can add 20-30% to the SAE net figures to get what it would be in “’60’s� hp. The problem though with trying to directly compare ‘60’s hp figures to ’70 and later figures is that a lot of the ‘60’s cars got under rated for insurance purposes. Example: 426 hemi was rated at something like 425hp at around 4,500rpm. The engine was capable of making hp clear up to around 6,000rpm. This actually meant that at 6,000rpm it was pushing out closer to 500hp. Now if you knock 30% off that figure to get rear wheel horsepower (NOT SAE net, SAE net is NOT at the rear wheels) you get approximately 350hp at the rear wheels. I was watching one of those Dream Car/Two Guys/TOO MUCH MONEY shows that dynoed a real Hemi Cuda and it put down 320hp at the rear wheels so the calculation isn’t a bad rough guess.

I got a buddy that has a '70 Road Runner that's putting 414hp and 458ftlbs to the rear wheels. Given that the car is manual trans. and no options I'll say it burns up 20% to the rear wheels so that's about 496hp at the flywheel.

For 184hp at the tail shaft of the trans. and AC guessing 20% loss 220hp at the flywheel.