I was breezing through some old Hot Rod Magazines may 98 to be exact. And I stumbled across an article called Who's Jivin' Who? The Dyno don't lie... And they use a Dynojet 248C chassis to dyno several vehicles from the 98 Eldorado, Dakotas, Vipers, Cobras, and GTP's
But the most shocking runs are the 98 Trans Am vs. the 98 Corvette. Mind you these were done by the professionals at Hot Rod magazine using both factory cars. No intake. No exhaust. Just straight factory performance.heres the facts.

'98 Pontiac Firebird Trans Am
Miles On Test Vehicle: 4,233
Engine 5.7 OHV LS1 V-8
Transmission 6M
Rated Power: 305 Hp at 5,200 rpms
335 lb-ft at 4,000 rpm

Dyno Observed Power:
292.8 Hp at 5,400 RPM
307.5 Lb-Ft At 4,400 RPM


'98 Corvette
Miles on Test Vehicle 5,237
Engine 5.7 OHV LS1 V-8
Transmission 6M
Rated Power: 345 Hp at 5,600 rpms
350 lb-ft at 4,400 rpm

Dyno Observed Power:
285.6 Hp at 5,400 RPM
301.2 lb-ft at 4,100 RPM

Winner '98 Pontiac Trans Am with 7.2 HP!

What they say: Because we tested the Pontiac Trans Am first and were duly impressed by it's near-300 Hp rear-tire reading, we expected the Corvette, with an extra 40 advertised Horsies, to deliver in the neighborhood of 320 Hp to the road. We queried tuners and members of the late-model performance aftermarket who unanimously suspect GM is installing the same 5.7L LS1 motor in Z28's, Trans Am's, and Corvettes. Yes, the intake and exhaust tracts differ somewhat, but according to these sources, not enough to account for significant performance desparities. So what we appear to have are slightly overrated Corvettes and grossly underated F-bodies. Regardless of paper-and-ink power ratings, any of these cars is capable of sub-6 second zero-60 and mid-13 second times off the showroom floor, and that's all ya really need to know.

page 46 Hot Rod Magazine May 1998.


Wow thank God Dad kept all these old hot rod magazines. by the way he's the reason I'm into f-bodies. I remember him and his friend Ron restoring a 79 Z28 when i was like 10 and I've loved camaros ever since.

 

That's what everyone has been saying in the forum all along. No tricks, the corvette is GM's baby and gets the higher horsepower rating. The rating thing has beem wacko forever. Back in 1965, The 396 was rated at 425 horsepower at 6400 RPM. GM had a policy of nothing over 400 horsepower except in Corvettes. So,,,,, in 1966 they gave the Same 396 a bigger carb and called it 375 horsepower except it was at 5600 RPM. If Y'all know anything about peak power numbers, all They have to do is pick the RPM that has the power at point of the rating that They want to see, Say a ZL1 makes 500 horsepower at 6500 but They want it rated at 430, all They do is look at the Dyno sheet and pick the power at 5200 RPM where it made 430 horsepower. Although it makes well over 500 horsepower at the higher RPM, They would play the rating game and pick the 430 HP @ 5200 RPM for advertising and insurance purposes. So don't believe most of what You read about Horsepower Ratings.

 

Most tests show peak power, what is really important is the average power throughout the RPM range, and very few of the published tests show that.

 

Very true Pete.

 

Really nice bit of information. Thx for sharing this