Horsepower change from 1971 to 1972?

[Silvius]

I have not been able to find a definitive answer on whether horsepower actually dropped from 1971 to 1972 models. I know the rating methodology was different; a 1971 350 was rated at 255 gross horsepower and the 1972 was rated at 175 net horsepower. While I understand that the ratings were changing in the industry at that time, my question is:

Was compression lowered for these trucks in 1972?

Was the actual horsepower the same from 1971 to 1972?

The answer may already be on the board, but I didn't find it in my searches; only explanations of the different methodologies.

Thanks for any help!

[67_C-30]

Originally Posted by Silvius

I have not been able to find a definitive answer on whether horsepower actually dropped from 1971 to 1972 models. I know the rating methodology was different; a 1971 350 was rated at 255 gross horsepower and the 1972 was rated at 175 net horsepower. While I understand that the ratings were changing in the industry at that time, my question is:

Was compression lowered for these trucks in 1972?

Was the actual horsepower the same from 1971 to 1972?

The answer may already be on the board, but I didn't find it in my searches; only explanations of the different methodologies.

Thanks for any help!

Compression was the same, and for the most-part they were the same engines. The rating system changed, but the engines performed the same from 71-72.

[JameslovesJammie]

Anybody have torque figures for same engines?

[Jtrux]

My sticker on the fender said 250 hp and 350 torque but the torque numbers sound kind of high to me but that's what it said.

[67_C-30]

1971
V8-350 4 BBL 8.5 CR 255HP@4600 355TQ@3000

1972
V8-350 4 BBL 8.5 CR 175HP@4000 280TQ@2400

Source: MOTOR'S Truck and Diesel Repair Manual - published 1973

[Silvius]

Thanks for the input!

[ChevLoRay]

The difference in ratings from '71 to '72 are the difference in BHP vs. SAE ratings. Old School way of rating horsepower was Brake Horse Power, a system used (and abused) for many years. SAE (Society of American Engineers) was a standardized system of rating that enabled the "leveling" of the playing field. This came about at a time when engines of some makers were under-rated, in the horsepower game, and had an unfair advantage in racing. For instance, the original Z-28 engine (the 302) was rated at 290 HP. In reality, if I remember Hot Rod from the era, it was closer to 320 HP. Same thing with the Boss 302, the Hemi, the ZL-1, L-88, etc. People assumed they had less horsepower, when it was just rating system that changed it. My new '71 VW had a 60HP engine but in '72, it was (I think) 57HP...maybe less.

When the smoggers came on the scene in '73 and especially '74-75, they did have less horsepower. Lower compression, restrictive carbs, antiquated (by our standards) emissions controls and ran like dogs. Engine run-on (dieseling) was common-place. That required an engine stop solenoid to help cure. No computers to read the data and make adjustments on the fly. We actually had to read the plugs, adjust the carbs, play with the compression, and use outhouse ingenuity to achieve better results from the crappy engines that we had to use. Oh, the play on words is intentional. I wanted to use other words, but that wouldn't be nice, would it? This is a family-friendly site.