Horse power changed in 72 from the crank to the to the wheel also from gross to net what is it now

Well it's still "net" and I'm assuming it's done at the rear axle, er, I guess I mean the front axle http://www.chevelles.com/forum/smile.gif now days.

Could someone please explain to me how bhp differs, you know back in the '50's when Chevy's hot new small block was out, they would use "brake horsepower" measurements. What is this and how did it work?

The way I understand it was measured on a dyno with open headers and no accessories.

The difference between gross and net is that the old gross numbers were made with a low restriction exhaust system, no water pump or alternator loads and an optimized inlet stack (chrysler even resorted to a cooled inlet stack on some tests).The net numbers are more like what you get in a real car: real exhaust, water pump and alternator in operation and a standard air inlet. Also, the correction factors changed from 60 degrees Fahrenheit and sea level to 85 degrees and 500 feet elevation. All of this is measured at the crankshaft with a dynamometer (or "brake") which may be like a large electic generator or may be a hydraulic pump to load the engine.

[This message has been edited by JWagner (edited 06-02-99).]

Back in the "good-old days," most manufacturers rated HP in terms of Gross HP. This was HP at the crank without any accessories, the coldest air-charge you could get, and low humidity. All of the auto manufacturers blatently over-rated there HP figures and the numbers you hear from the original GM, Ford, Chrysler,...specs aren't very accurate. Today, HP figures are rated in SAE net HP. There are many different sets of conditions but you will see something like (SAE J13430 HP), generally this is around 70 degrees air temp with about 60-70% humidity if memory serves. All accessories are connected and running as well as a full exhaust system. Also, BHP (brake horsepower) refers to horespower derived from an engine dynomometer that utilizes a pony brake, mostly a water-brake dynomometer like the SuperFlow 900 which is currently the industry standard. Hope this provides some clarity.