Hey Guys,
I'm new to this message board, this is my first post.
My fathers looking at a '72 Chevelle SS w/350 and 4-speed...only 5,800 original miles!!! I'm a bit confused about the horsepower ratings on these things... for a 1970 Chevelle the most power from a 350cu. was 300hp, while in 1972 it was only 170hp. I know the beginning-middle of the '70s was the end of the muscle cars, but is this drop in hp true??
Someone told me that HP ratings changed from HP at the crank, to HP at the rear-wheels, in which case, 170hp doesn't sound too bad...
I know this is probably a dumb question but any help would be appreciated..thanks

Hey,
I'm pretty sure the 350's mated with 4 speeds in 72 were rated at either 165 or 175 HP. Also I think that's at the flywheel. That's basically all that I can tell you, besides stuff you already know.

72 was the first year of "net" hp ratings, where 71 and earlier were "gross" hp ratings.

Virgil

I Think Trever has it right. For the Chevelle in 1972 the two 350's available were the L65 350 2bbl carb that was rated at 165 horsepower (which my 72 originally had) and the L48 350 4bbl carb which was rated at 175 horsepower.

Horsepower was still taken at the flywheel but with all acccessories installed. Alternator and stuff like that. I think even the exhaust was installed instead of open headers.

1971 and before the horsepower was done at the flywheel and with open headers just like your regular speedshop would do.

Just think about this the 71 and the 72 engines were equipped pretty much the same except some distributor differences maybe. The L-48 in 71 is rated at 270 gross hp and the L-48 for 1972 is rated at 175 net horsepower. That is a 35% drop in rating the horsepower. Sort of like cooking the books in Washington D.C. to make the deficit look smaller. They just wanted the insurance people to think the engines had less horsepower than they had in 1971.

Hey Guys thanks for your help!

One more question, Virgil, you mentioned that in '72 they used --"net" hp ratings, where 71 and earlier were "gross" hp ratings-- so then is there any way to figure out what the "gross HP rating for for this '72 350cu. is?? I guess it would be similar to the HP figures for the '71s then right?

Just curious thats all smile.gif Thanks!

Larry "Plain 69",

I just read your reply, thanks...it makes a little more sense now!!!

There's no way to "figure" anything about the older HP "ratings". Note that I put the word "ratings" in quotes, because they weren't "ratings" at all int he modern sense. That is, those motors didn't put out onywhere near that kind of power. They were pure ad copy.

One of the absolute funniest ones was the "375 HP" 327, the L79. That as many will recall was a 327 with very small dome pistons, double-hump heads, and a "151" cam. A good running motor but certainly not a racer. If you build that motor today and put it on a dyno, I'd about be willing to eat it if you could get 325 HP out of it. Once in a car, it is probably good for about 260-280 HP.

In 72 they changed to actual measurements made on real-world motors, instead of pure unbridled fantasy. The later ones are with the motor as installed in the chassis it's meant to go in; with full exhaust, air cleaner, all "accessories" (emissions controls, not things like A/C) installed and operating, all essential accessories like alt, WP, etc. operating. The change from fantasy-land to reality usually reduced the "ratings" by around 30-40%, sometimes even more than that.

So just enjoy the joke of the old 60s "ratings" when you see them, and realize that most of the time they have little or no connection to what the engine was actually capable of.

RB69SS396Conv your just about right on everything except an L-79 is only rated at 350 hp in 66 and the 67 Chevelles were rated at 325hp.

The 375 hp 327 also had fuel injection as well.

You also would have to think that when they dynoed these engines they were probably not your regular engines just off the production line either. The ring gaps were probably perfect dead on and ignition timing was dead on as well as the carboration.