old hp vs. new hp Hope someone can help. I understand that in the early 70's they changed the way that horsepower was rated. How does that compare to the new way? For instance, a 1966 Buick 310 Wildcat has 220 hp. A 1980 Olds 350 has 170 hp. They were tested differently. If they were both tested the old way, would the newer motor have more hp than the 170 it's rated at today? If so, how much? How are these hp's calculated? Thanks for any help. By the way, I love this web site. It is soooo informative. Jim
Hey Jim, Good to hear this board is helping out:TU: Word of advice: If you have a question specific to any given forum, post it in that forum. If it's a general question like you have here, then post it in The Bench forum. I see you've put this question in a few forums...which is fine, but it clutters things up more than they need to be. The Bench gets LOTS of traffic and your question will be answered in good time:TU: :grin: If you post the same thread in 3 different spots, then you'll be getting lots of redundancies and mix-ups in the answers...so try to keep it simple. To try to answer your question... In 1972 they changed the HP ratings from GROSS to NET ratings. This substantially decreased numbers and really confused everyone. The ACTUAL HP ratings really didn't differ much from 71 to 72. Although in 72 you saw lots more smog crap and EGR junk being added to engines...and that did play a part in the decrease in numbers between the years. HTH:Comp:
Jim, Things have changed alot from when they started measuring Hp and torque. In the old days they measured the force needed to move 550 lbs, one foot in one second, It was called a pony break, we've come along way.:beer Nowadays Hp is measured at the rear wheels even though it's not the highest hp point which is at the crankshaft. The theory is, the power you use is at the rear wheels. Being somewhat new to this myself i'm not sure how they Dyno'd moters back then but I know nowadays it's very complex and they use all kinds of factors that i'm sure were not available in the early 70's. as far as how they come up with the numbers: If I remember right it's Torque x Rpm / 5252 = Hp I hope this helps ya,,,,,:TU:
Just to clarify here, the old "gross" system they would simply bolt the engine to a dyno with no alternator,p/s a/c, water pump or exhaust and let it go nuts......when they switched to "net" in 1972, they now measure the HP with all accesories and exhaust...it is NOT rear wheel horsepower, that is another thing altogether, but it is the flywheel output you could expect from the engine installed in the car. You usually lost about 60 hp going from Gross to net on a V8 Buick. Thats why a new ram air TA with 320 HP will kick your ass, in 1970 that engine would have been 380 or so..... Look at all the engine specs for 1971, then in 72 you see a huge drop. As mentioned the smog stuff didn't help but no way it cost you 60 HP. Take away another 20% from the net and you will get a rough guess at rear wheel horsepower. Does that help?? later Tim
HP ratings One other factor to consider when comparing HP numbers - in the 1950's and 1960's horsepower was GOOD and was used by manufacturers in their advertising to help sell cars. In the early 1970's horsepower became BAD, at least when it came to buying car insurance. Things got so bad with insurance costs that you could easily spend more on insurance than you would on car payments for many musclecars. As a result, the manufacturers started under reporting HP. This is why you'll see expensive engine options that added only 10-15 HP to the rated HP on cars like the Stage 1 Buick and the Ram Air Pontiacs. The real numbers were higher, but the "advertised" numbers were kept low to try to make insurance affordable.
Well the factory net rating on my 72 GS convertible 350 four barrel, dual exhaust is 195hp. The regular 350 was 185 I believe. Every engine is different, the only real way to get numbers is to put it on a dyno and go from there. I would think the smaller engines would lose less HP so you are probably closer to 180-200. depends on accessories and engine. Of course, put a four barrel on and a camshaft and it goes way up....especially because the 68 has higher compression than the 72. later Tim
