It was falsely advertised as 305HP in '98 - '00 then upped to 310 in '01 and '02 for the Z28. What was the real difference? And what is the average HP a '98 - '00 Z28 making at the wheels? What is the average HP a '01 and '02 making? All stock of course.
Also, what is the gas milage of a '98 - '00 LS1?

Thanks in advance...

 

I think most of the improved power if from the LS6 intake, but they also changed the cam and a few other minor things.

My '01 T/A dyno'd 311 rwhp/334 rwtq at 1800 miles bone stock (not even broke in).

My old '98 Z28 dyno'd 316 rwhp/330 rwtq with a ported MAF, Whisper lid and SLP 2OTL cat back at 13K miles (broken in).

Gas mileage in both has been 17-18 in town (heavy foot) and 28-29 mpg in sixth gear on the highway.

Bottom line, the '01-'02 cars are faster.

 

The 98-00 model cars do have a more aggressive cam than the 01-02 cars though. I'd say 01's and up have about 10 hp on previous years but then again every car is different.

 

The numbers advertised by GM were in reality be putting down at the wheels. Very big difference in FWHP.

 

98' - 00' LS1's dyno stock at about 305 RWHP
01' - 02' LS1's dyno stock at about 315 RWHP
The only differences are the cam (not milder) which has greater midrange torque and the addition of the LS6 intake and block. The torque curve on the 01' -02's is flat from about 2K to 6K with a slight peak at 4200 rpm. My last dyno numbers are pretty stout considering the minor mods made to the car. 352 RWHP 361 RWTQ, these are SAE corrected averages under the curve not peak numbers.