WE ALL KNOW THAT GM DOWNPLAYED HORSEPOWER RATINGS FOR INSURANCE COSTS AND EMISSIONS, BUT DOES ANYONE HAVE OR KNOW WHERE I COULD FIND THE "REAL" HORSEPOWER OUTPUTS OF THE C3 MOTORS?

I don't know of any actual dyno pull articles about those 60's-70's muscle car motors. I've heard lot's of stories about 500-600HP Hemi's and ZL1's. I'm sure that if you've got Smokey Yunick or Bill Jenkins running the tests, and setting everything up the right way, they probably pulled some pretty amazing numbers out of those engines. Unfortunately, guy's like me just aren't as knowledgeable about jetting and timing curves and things. I have a 454HO crate motor with a ZZ502 cam that could be making close to 500 at the crank if I was a professional tuner, but common sense leads me to believe that all my driveway tuning probably has me somewhere closer to 400(less than the factory 425HP rating with the stock cam). I guess there's potential, and then there's reality. I'll bet some of those old Mopar 440's with the six packs were consistantly less powerful than the same motor with a single 4BBL, simply because they were harder for a regular guy to keep in tune. Didn't really help much with your question, just seeing if we can stimulate a little activity. Good luck

I WAS JUST WONDERING BECAUSE I KNOW, EVEN AFTER 26 YEARS OF DRIVING, THAT MY CAR STILL HAS MORE THAN THE RATED 220HP.

Here's yet another twist to horsepower numbers, in 1972 GM was forced to switch to net ratings instead of crank hp ratings. Plus, at the same time emission controls were showing up, octane levels were dropping, and leaded fuel was being phased out. It makes it very difficult to compare performance from year to year.

Engine HP ratings from the past are great reference points, but should never be considered as the rule. That 220hp is an average number that GM provided, based on testing of multiple engines with the same configuration as yours.
1. Two engines with identical parts doesn't mean identical numbers.
2. As mentioned above, all car companies "fudged" thier numbers, for insurance purposes.
3. H.P. ratings in the 60's/70's were obtained by someone with pencil and paper standing next to a Dyno watching needles swing. Two different people could Dyno the same engine on the same day and get different numbers.
New cars are tuned for emissions and milage, so there is ALWAYS more hp hiding inside. Timing, fuel mixture ratio, air intake and exhaust restrictions are all hp "hiders".

Look at the current GM "Goodwrench 350" crate motor. You can look at several different dealer ads, and see this engine rated anywhere from 185hp-210hp. Probably depends on what each dealer obtained from Dyno-ing one themselves or from GM provided numbers.

I would look for magazine articles/reviews from when your Vette was new, like Hotrod or Popular Hotrodding.

|UPDATED|4/27/2003 2:07:59 PM|/UPDATED|