Can anyone shed some light on the power ratings. I knwo that 71 were reduced in C/R as compared to the 70. I believe that the only difference between 71 and 72 was that the power rating was taken at the rear wheels (net) and in reality the 71 and 72 were indentical. Any facts would be appreciated.

You hit it right on the nose, before 72, the engines were tested sitting on a stand, no accessories, air cleaners or mufflers. To the best of my knowledge, they are pretty much as they were in 71. LS5 in 71 rated 365hp gross, LS5 in 72 rated at 270hp net, showing a 25% reduction. I had always thought the loss was about 30%, then I just read an article that said it was 20%, but when I sat down and figured out the LS5's, it worked out to 25%.
71 LT1@330hp, 72 LT1@255hp = about 22% loss

I was always under the impression that gross HP was the engine on a stand with no accessories, net HP was the engine on a stand with all the accessories and rear wheel is ( as it indicates ) rear wheel HP. A supposed loss of 15 to 20 % from gross to net and another 15 to 20 % from net to rear wheel.
My 427 is rated 390 gross but the dyno shows 248 rear wheel which is a loss of 142 which is about 36% of gross. Doing the math, that is -78 ( 20 % ) from gross and -62 ( 20 % ) from net, give or take a few. That would all depend on your accessory load and the transmission, clutch or torque converter loss etc.
Hopefully I will get a better feel for this if I ever get my engine back and can assemble it and get it to a dyno for tuning before it goes into the car.

|UPDATED|5/13/2003 10:53:25 AM|/UPDATED|

Not sure if this helps, but I referred to it quite a bit before getting my '79

http://www.cccvette.com/fast-corvettes.htm