Kevin84Z28

iTrader: (3)

From time to time I've heard that Chevrolet or GM (et al) under reported the horsepower of their motors. The story was always told about how CARB, FED, and the insurance industry regulations necessitated the lower numbers. I did a search on the internet for giggles and found an article that stated,

"Horsepower was measured in NET rather than gross rating beginning in 1975.
This meant that the reported horsepower was much lower than in prior years. The 350 cubic-inch V8 was now rated at about 155 horsepower."

That would be a "reported" loss of about 40 H/P from the 1974 base 350 c.i. based on a means of statistical semantics.

Wouldn't that mean that a L69 would have a GROSS 230 H/P, LB9 255 H/P, L98 260 H/P, Etc...

Here's a link to the article. Not much interest to it, just the one notation about H/P.

http://www.conceptcarz.com/vehicle/z...et-Camaro.aspx

AmorgetRS

iTrader: (6)

Net Horsepower is a much more accurate measure of a cars true crank HP compared to Gross. Gross meant basically no air cleaner, no accessories, no nothing to hinder the motor at all. That is where the difference comes in.

GM did under rate certain motors, like the LS1. Mine dynoed bone stock at 294 RWHP, it was rated at a measly 305. My 91 GTA dynoed at 170 RWHP, rated at 205 hp. Seems pretty accurate to me.

Guest

HP numbers for thirdgens seem to be fairly accurate, based on 1/4 mile times and dynos.

The changeover to SAE Net was 1972. As mentioned, its more realistic. The SAE Gross numbers were one off dyno motors with no accessories or anything else for that matter. The SAE Net was supposed to report a HP number that would be the HP you'd get as installed in the car, measured at the flywheel.

Kevin84Z28

iTrader: (3)

I agree with the reasoning, it's the perception that's developed. Say a person has a 1969 Camaro SS with a 325 HP 396 c.i. In the day they would say 325 H/P because of the way they determined H/P. If it was measured in today's standards it might be a 285 H/P 396 c.i. If my L69 were measured in Yesteryear's method, it might have been called a 230 H/P 305.

Orr89RocZ

iTrader: (20)

I feel the L98 was underated. 230-240hp in 89 or so, but my car easily made 220-230 at the tireswith just exhaust. Stealth ram swap and 1.6 rockers i put down 254whp and i was very lean.

I dont see an intake swap gaining that much power with stock heads/cam. Stock L98's have been known to dyno mid 2-teens. I've seen 210-230 whp stock or so with varying years L98s between vettes and fbodys. I think they were closer to 260-270 stock

Go figure the LT1 was rated at 275-285 hp but I"ve seen stockers with catbacks put down 260 thru the auto and closer to 280-290 with manuals depending on the years. LT1's have better intake, abit better heads and abit bigger cam, but i dont see how those smaller differences would change the L98 from 230 hp to LT1's 280 or so. L98 and LT1's are slightly underrated. LS1's even more so

GM has been doing that for awhile now. Even the new 2010 camaro SS put down 360's whp

okfoz

One thing that I notice is the 300 HP cars from the 60's perform about the same as our 220 HP variants. You look at Quarter mile times of late 60's Camaros and they are in the mid 14's... Just like most of the 350 powered thirdgens.

TOM-1LE

As stated, the thirdgens are pretty accurately rated in terms of net horsepower (except the '89 TTA -- see below). GM has been known to underrate some engines -- the LS1s were well known for this.

One of the most notoriously underrated engines of the last 25 years was the Buick Grand National/Turbo Regal of 1986/87 and Pontiac Turbo T/A of 1989. For corporate image reasons, and due to its rather rudimentary chassis and poor braking performance, GM did not want Buick to advertise the GN with substantially more horsepower than the Corvette's 230-240 (86/87). Therefore an "advertising" decision was made to rate the GN at 235-245 horsepower (86/87). The TTA was rated at only 250 hp (versus the '89 Vette's 245).

The GN's actual output was estimated by magazines of the day to be around 285-300 hp, far beyond the Corvette.

AmorgetRS

iTrader: (6)

I believe that would be that they actually Over Reported the HP of those earlier cars more then they under reported the HP of Thirdgens.

scottmoyer

I think I mentioned it before that a guy I knew in Minneapolis mentioned to me that it was a disgrace that my car said Z28 on the side. He stated that a "real" Z28 has performance, power and speed. That same day, I raced him and it was an even race. His car, original 1969 Z28 with factory headers against my stock 350 IROC-Z. My car is rated at 225hp, his at 290. Take the parasitic loss into account on his car with Net vs. Gross hp ratings and the cars are equal.

After the race, he acknowledged that the IROC-Z was worthy to wear the name Z28! He had just never seen how fast it was and was ignorant to the power and performance behind the L98.

TOM-1LE

Most people, even self-proclaimed "car people" are unaware of the gross vs. net SAE HP rating change that took place in 1972. This, plus the rose-colored glasses that some people remember the old muscle cars with, automatically leads them to assume that a stock '69 Z/28 has 65 more true horsepower than an L98, which is not true.

I think the reason most people "remember" the older muscle being so great is that some of the "average" cars were truly slow back then. Anyone who is used to driving a typical 307 2-bbl Impala, 6-cyl Maverick, 6-cyl Nova or 48-hp Volkswagen, all of which were extremely popular cars back then -- yet were lucky to run the 1/4-mile in 20 seconds -- would consider even a 14-second car to be a wildly powerful beast.

Today, many ordinary family sedans have over 200 hp and can run 15-second quarter miles. This has changed what we perceive to be "fast," but the reputation of the old stuff continues to cast a long shadow, true or not.

Kevin84Z28

iTrader: (3)

Yes...exactly the point I was making. I've always read about (and had a few) of the 60's and 70's muscle cars and their big H/P motors, verses the anemic third gen with it's smogger 305 or 350, when everything being equal they're not that far apart if not spot on the same.

91interceptorZ

iTrader: (3)

chevy did underate a few motors...back in the day....the old rare 427 corvette stingray....I believe rated at 425hp but actually put out in the 600hp range.....there were talking about it on a barret-jackson auction.....car went for a crazy $$ amount.....I know not camaro related but anyway....I don't know what year or many details cause it was a vette and I was just kinda watching it.......