Can someone explane to me net verses gross horsepower. I had a 1962 FI Corvette that was rated 360 hp. Now I have a 2002 LS1 rated at 350 hp. How do these two engines rate against each other in hp and torque??? Which powerplant has the highest rating and how were they rated. Thanks for you're time...

 

I am not too sure how to compare your C2 to the C5, but there is rear wheel horsepower and crank shaft/flywheel horsepower. The horsepower of any car you buy is quoted as crankshaft horsepower or the amount that is produced at the engine (ex. Ls1 350). However, we only really car about rear wheel hp because that is what gets the car moving. There is usually about 15-20% of horsepower lost through the drivetrain, generally more is lost with automatics than manual transmissions. So if you have a manual ls1 350hp, then you should have about 15% less or around 300 rwhp.

 

Here are a couple of definitions that demonstrate the difference.

SAE gross horsepower:
A production engine's actual power available at the flywheel or output shaft (usually crankshaft) as tested with an absorption dynamometer. It differs from SAE net horsepower in that many of the accessories (such as alternator, water pump, etc.) are not attached. Engines before 1973 were primarily measured with these "gross" numbers. Since 1973, "net" figures were published. This confusion caused many people to suppose that their engine had been seriously de-tuned when they saw that the same engine in 1972 had 400 hp but in 1973 had only 235 hp. (This example is from the Cadillac 500 cubic inch engine).

SAE net horsepower:
The brake power (power available at the flywheel or output shaft -- usually the crankshaft) of a fully equipped engine fitted with all the accessories necessary to perform its intended functions unaided. In 1973, automobile manufacturers began publishing their engine specifications in "net" horsepower and "net" torque instead of "gross" figures. In many cases the published numbers were significantly lower in 1973 than in 1972. Some of the decrease was attributed to the addition of pollution equipment, the lowering of compression, and the use of regular unleaded gasoline instead of premium leaded fuel. However most of the decrease in number was a switch to "net" figures.

 

I don't recall the exact time when the switch was made, but during the early years the horsepower reported was 'Brake Horse Power' which was measured at the engine without all the auxiliary equipment, like the generator and waterpump, attached. Horsepower measured this way came out at about 80-100 HP more than if it was measured like we do today. Your 360HP C2 probably corresponds to a current HP rating of 260-280. Someone please correct me if I am wrong.

 

What would be great is if a member of the forum who owns a C5 and a C3 could have them dynoed and see how they compare. That would give us a pretty good idea between gross and net ratings.
I use to own a 69 427/435 (3x2). I would be real interested in how my 98 and the 69 matched up horsepower wise.

 

Muscle cars of the 60s ran mid 14s to high 12s with 7" slicks and tuning as street driven cars.
Grumpy Jenkins or Sox and Martin, etal ran a lot quicker turning them into real race cars but that is a different story.
12 second cars were only the top of the list - street hemis, 454 chevelles, 427 Corvettes and Camaros, etc. and that was only accomplished with slicks, good tuning, low gear ratios, maybe headers but certainly open exhaust (dump tubes).
A good running show room stock C5 will run in the high 12s low 13s on a good track and weather.
The early cars and today's Corvette and F bodies weigh about the same so do the math. LS1 is rated 350 hp at the crank and the big motor muscle cars were rated 400 and up and there was always talk that they were often underrated by the manufacturers.
The 62 fuelie wouldn't stand a chance against most any C5.

 

I saw on tv one time they basically said engines back then were rated at the crank with no accessories...just the real power the engine was capable of producing, not what it was actually going to be able to use while in the vehicle in a real life scenario. I built the motor for my brothers 68 Mustang quite a bit stouter than stock and I still don't think it would keep up with the ol C5

 

Thanks everyone for you're time and input.....