84 Z28 5.0 HO

HI
i would just like to know if anyboy has tested the hp ratings on the 1984 305 5.0 H.O.
Its it rated at 190 hp stock but that seems a little low. I know GM underated the hp reading on some cars in the 80's


thanks,

ME Leigh

I don't think its underrated.

Vader

If I'm correct, that's SAE net HP, with the engine installed in the vehicle, exhaust connected, accessories on, and measured at the wheels, so all driveline losses are accounted for.

v8unleashed

iTrader: (3)

are all of the modern day measurements of hp are at the wheels?

and didnt that change at some point in the 70's, explaining why some cars had monstrous hp numbers in previous decades?

dimented24x7

iTrader: (2)

someone told me SAE net was measured at the output of the trans, is that true?

ME Leigh

SAE net hp rating are measured at the flywheel, with all of the available accessories connected and running, stock exhaust, and everything like the production vehicle will have.

v8unleashed

iTrader: (3)

so am i wrong about the older cars? or were they measured without accessories, and that's how they registered so high?

MattW

iTrader: (1)

my 190 HP H.O.e runs a 14.7
so who knows if its actually 190 hp

Sickness91Z28

iTrader: (1)

I used to have a an 84 Z28 H.O. (1992 Z28 Clone)...the High Output L69 package 305 REALLY surprised.....I noticed a big difference between a stock 305. I too heard that the H.O. were rated at 190 HP.....that took me by surprise...

ME Leigh

Older Gross horsepower ratings used all of the performance goodies to measure the power output. Bigger carbs, headers,better intakes, good exaust, no accessories. And sometimes higher compression and other things not seen on production engines.

Vader

In 1972, the entire industry switched from SAE Gross HP ratings to SAE Net HP ratings.

SAE Gross (or Brake HP) was measured at the flywheel, no alternator, PS pump, water pump, other accesories, no air filter assembly, no transmission, and tuned for maximum output at 60°F and with the best fuel available. Intake and exhausts were optimal for making peak HP. Fuel mixture and timing curves could be adjusted anywehere the tester wanted. Engines were typically tweaked just to make the best dyno numbers, and probably ran like crap a idle an lower RPMs in that same trim.

The SAE Net ratings required all accessories (including things like mechanical fans that were inadvertently "forgotten" in the old rating system) were mounted and operating, at a higher 77°F / 39% RH standard for test air, with the engine in normal tune, as delivered with full factory exhaust system as installed in car, full intake system with air filter. Measurements were still taken at the flywheel, but with pump gasoline.

For example, a Cadillac 500CID in 1971 made 400 hp, but the very same engine in had only 235 hp. Same bore/stoke/compression, same heads, same valves, etc.

For another example, the 1972 LT1 was rated at 330 hp (SAE gross) / 255 hp (SAE net), 370 lb./ft. torque peak.

It is rumored that GM artificially lowered their numbers on some engines even more by testing with transmission connected, and the HP reading was derived from the output shaft of the transmission, NOT the flywheel. this was in response to intense auto insurance industry pressure to lower the HP of vehicles to make them "safer". I guess it didn't take a lot to fool a pencil pushing accountant at an insurance company into lowering the annual premiums.

SAE net HP numbers (and actual outputs) continued to decline during the "dark ages". Emission control systems were relatively new and untested, combustion chambers were enlarged to control detonation from the "camel-urine" embargo fuels and to reduce NOx emissions before the advent of EGR. And possibly more ominous, public pressure for big HP engine was increasing due to the general public's ignorance of the fact that increased efficiency is the same as more power in any given engine. Some people still haven't learned that. Around here, we call them "liberals".

As systems became more sophisticated, and liberals were learning that low power didn't equal better efficiency and cleaner air, compression ratios were increased, timing was added, intake and exhaust flows were improved, and the power outputs increased in line with increased efficiency and lower emissions (DUH!). What we had been saying all along was becoming evident to the not-so educated, but vocal minority. (The important point here is that if you take away the tree that the liberal is hugging, machine it into a large wooden club, and vigorously beat them about the head with it, they'll either learn to research and learn before opening their mouths, or be beaten into blithering, Caravan-driving ignorance.)

Current test numbers still don't reflect drive line losses, but I expect that in an effort to equalize the ratings systems again, we'll see a change in the future to actual road wheel power and torque. So much for all those "260 HP" Toyotas. We'll see Road HP number drop again from the current advertised levels, but we'll also see the skinny-tired FWD and AWD vehicles drop dramatically from their currently inflated ratings. Sure, the 220 HP Mazda can make 220 HP, but at 6,800 RPM and with so little torque that it probably won't overcome a lot of wind resistance at anything but that RPM. They won't last long at that rate, no matter how well assembled they are. Ask Mazda how long the warranty is in effect if you operate at rated HP for daily driving.

Damon

My personal experience with an L-69 5-speed car (190HP rating) was that it was about 1 car length behind a stock 5-speed 5.0 Mustang (rated at 225HP by Ford) through the 1/4 mile. Sounds reasonable until you factor in that the F-body was at least 100 lbs heavier than the flyweight Mustang. Seemed to me like the 'Stang was overrrated or the Z was putting down a little more than it's factory rating. They were surprisingly fast cars.

NTChrist

Vader!!?! Where did that come from?