speedlink

LT1. Better handling etc.

1985 Corvette

Who believed the hp ratings GM use to slap on the old big blocks back in the days? C4 LT4 was a tad underrated (nowhere near what some LT4 zealots believed it was for real hp output). It isn't surprising GM sandbags on hp numbers.

Shurshot

That would not surprise me

Actually I would SUSPECT the old 426 Hemi to be less than 425 HP @ the crank

I am guessing by comparing it to the L72 425 HP 427 that put out an actual average of 380 HP at the crank,

Most old 427 vettes did not make even make 300 RWHP unless they had just had a fresh tune............ but for their day they were as good as it got and now they do it with high $$$ numbers

Big Dan 427

Was wondering the same thing.

Mostly speed! I agree with what you say except for the C6 part, I think most who will still buy a C6 have committed to the styling and deep discounts. I think with the price 6's are going for the hit won't be as bad as most think if folks want to trade up in a year or two.

I'm still confused by his question, it's as if he's asking (b/c he did say if all else was equal) is the LT1 at 450 more stout than the LS3 at 480.
Am I missing something?

HurricaneRN

Agree, although I was curious so I searched the local inventory. In a 50mi radius encompassing 1.5mil people and a ton of Chevy dealers the c6 inventory is sparse. Bout the only thing you find is GS or Z models, especially at the 5 dealers with c7 allocation.

racebum

GM has done this more than once. wouldn't surprise me, the late c5z was under rated by 10-15hp

maybe they do their dynos in 100deg high humidity?

CPhelps

The SAE J1349 standard that GM certifies to would seem to make underrating a thing of the past, however maybe not?

I was looking around at GM's Powertrain site this evening and noticed something interesting.
GM has a Gen IV 6.0L truck engine called the L96 that is listed :
Chevrolet Silverado HD < 10,000 lbs 360 hp ( 268 kW ) @ 5400 rpm SAE CERTIFIED
and
Chevrolet Silverado HD > 10,000 lbs 322 hp ( 240 kW ) @ 4400 rpm SAE CERTIFIED

Notice the difference in the engine speed when they did the rating.

Now look at the dyno charts:
360 hp L96

322 hp L96


The power curves look very similar, perhaps with more smoothing applied to the 322hp version, but GM took the power measurement of the 322 hp L96 at 1000 rpm lower (4400 vs. 5400 rpm), but the chart clearly shows it making peak power closer to around 5600 rpm, and just about the 360 rating used on the other version. Both are SAE rated. The 360 HP L96 even appears to make more than the 360 HP at around 5600 rpm, from looking at the curve. This trick sound familiar from the L88 days?

What if the LT1 is rated at 450 hp @ 6600 RPM but the car is indeed actually capable of a higher rpm? Maybe track mode unlocks it? This would possibly explain why every specification listing of the LT1 has claimed max engine speed of 6600 rpm, however several bash attendees noted a speaker mentioning 7000 rpm in 4th gear, and also the SAE paper that had a plot of the LT1 going to 7200 rpm. It would certainly qualify as the "surprise" we have heard about for the C7.

Kind of far fetched I know.