an ex-tech moderator from another GM forum once told the LT1 actually makes about 290-295 horses at the flywheel instead of the 275 GM rated it at....is this true????? he said the reasoning was for insurance purposes and to preserve corvette supremacy. (he also said the LS1 actually makes the same 350+ hp as in the corvette instead of the claim of 310.) thatd be pretty kewl if i got "free" horsepower i never knew i had lolz

 

The only way to tell is to Dyno a stock car...I've never done it, but I hear they are around 250 at the wheels.

 

yes that is true GM also rates the Manual 6 speed trannies to hold up to 450 HP but alot of people have more of that going to them with no problems they tend to under rate everything just to be safe for the most part and the LS1's pretty much do have the same HP as a new vette but they want the vette guys to feel special so they under rate 1998-2002 f-bodies

 

That would be cool!

 

There is no Difference between the LS1's in the F-Body's and the Vette's... It's the same exact motor. They both dyno around the same rwhp but the Vette's IRS chew's up more power then the f-body's solid rear.
As for the LT1.. My old 6spd 96 SS Dynoed at 274rwhp stock... Factory freak? Maybe

 

LS1's are underrated but LT1 aren't really

 

Were definately dummed down. LT1's weren't as much. The only reason LS1 vettes are faster then F-bods is the weight difference. Gm likes to use the same engine a lot. New GTO will use LS1 and the performance model will use the current LS6 Z06 vette engine. LS1 puts out 340 LS6 supposedly 405. I'm pretty sure my M6 LT1 will dyno around 240-250 stock like it's supposed to.

 

Question. There is a percentage of HP loss that is expect from any vehicle platform that is lost due to drivetrain scavenge. What is that percentage? I know the percentage changes with different platforms, but what is the average number? I'm thinking it is 15%. If that is right, stock LT1's that dyno 250 RWHP, taking into account the scavenged %, would actually be around 288 HP. Well over the published 275 HP. This sound right?

 

yup, Bad1LeZ...the drivetrain loss percentage is y i asked... 250-260 RWHP seems to be too much if the engine only makes 275 i was thinking it was closer to 285-290 myself.

 

15% is a little high I think for most 4th gen fbodies. I thought they were a few % less because the t-56 is a really good tranny, and we know the rear end. Of course, automatics will see a little less.

The Lt1's are good for 275 or perhaps 285 flywheel... They're pretty much on cue. I asked some people at the dealership why the lt1 vettes were 300 - and was told a slightly more agressive tune and better exhaust manifolds.

Ls1's are more underrated. Perhaps in 98' to keep SOME interest in the older lt1 cars, perhaps also to keep insurance companies happy. They're fast *** cars!

 

The vette also has a dual exhaust, where the F body doesn't.

 

The LT1's rating is definitely closer to reality than the LS1. It's true, the LS1 f-body makes more like 340-350hp, not 305-310.

But the LT1 in most cases is pretty close to the 275-285 rating. I believe the SS and WS6 are overrated at 305hp though, since I haven't seen any evidence at the track that the LT1 ram air cars are quicker than the non ram air LT1s. None of the ram air LT1s in my club have come close to my 13.74 bone stock time. But if they've got 30 more hp, they should be running 13.4s or 13.5s bone stock. Instead they run 13.9s to 14.0s like most other bone stock LT1s.

I believe the same is true with LS1 ram air cars though, they don't seem to make more power than the non ram air LS1s either.

 

Drivetrain loss on an M6 LT1 is pretty close to 12.5%.

 

We all saw the magazines get 13.3s to 13.5s out of the ram air LT1s, but I bet if you asked 100 ram air owners on here their best ET bone stock, not many would be much better than 13.9.

 

I know for a fact that GM underrates all its vehicles. They dont use the peak power rpm. (It is also true that they were way off on the ls1). Ive heard the 93-95 lt1s are around 290 to 295 at the most, (at the flywheel) and 96-97s are around 300-305.