Steve Adkins

Back in 1969, did they measure HP at the rear wheels or fly wheel?

Ganey

Flywheel w/ optimum setup.

Steve Adkins

How much loss can you figure by the time it gets to the rear wheels?

1Bad69

I think you are looking at 15-20% depending on if it's stick or auto ...

TTop Tony

I'd be willing to bet its more then 15 to 20%. From what I've been told they had no accessories hooked up when they did the tests back then. A modern car has a 15 to 20% loss but they have the accessories hooked up when they measure them at the crank.

BB wowbagger

:withstupid: ....I belive thats the differens between SAE and DIN standards..When did they start to measure the engines with accesories :confused: :cheers:

TTop Tony

It seems like someone told my they started in 71 or 72. From what I remember the LT1 went from 370 hp to 320 (or was it 320 to 270) from one year to another without a change in the engine. Just a change in the way they measure it.

Steve Adkins

So a stock 69 350/350 with a 15% loss whould only have about 298 at the rear wheels?

TTop Tony

If I had to guess I'd say more like 250 at the rear wheels. but thats an uneducated guess.

Ganey

No way sto*k.

Gross to net ratings in 72.
71 LT-1 330 Gross 72 255 NET

Another ex. you may not be able to find! Have posted before.
425 Gross 325 Net

:cool:

Metal Wulf

I've always head that you take off 17% for the accessories, then another 15-20% for drivetrain loss.

so a 350/350 would be around 233-245 rwhp

:cheers:

sammyb

Yes, in 1972, there was a change Gross vs. Net. In addition, in 1972 GM lowered the compression ratio of all of its vehicles to run on lower octane fuel.

For instance, a 1969 427/435hp car was only 435 horsepower running on an engine dyno pulling absolutely nothing except the crank, cam, rods, rockers and pistons. In 1972, they lowered the compression then rated the engines while pulling the alternator, pumps etc. In addition, the horsepower ratings were slightly lowered on some cars to lower the cost of insurance. While I can't say I've ever seen a stock '72 on a dyno, there's a chance that some of the higher horsepower option cars were slightly underrated.

On modern C5s, where stock horsepower rating has been 350 for many years, the average stock dyno pull usually falls between 295-310 rear-wheel horsepower. 6 speed cars tend to pull higher numbers than the power-sapping automatic.

Sam