Question: C5 ZO6-Why two HP ratings, 385 & 405

[rrp]

This is my first posting. This site was extremely helpful when choosing my first corvette. I've just purchased a silver 2001 ZO6. What a great car. It has met all my expectations and then some! Thanks for all the great information.

Quick question; Everything I've read states the C5 ZO6 engine produces 385 HP, yet the insignia on the car says 405 HP. How is the 405 HP rating determined? Is that horsepower in relationship to the HP generated after the exhaust or some other factor?

I've wanted a corvette since I was five years old, 49 years later, its in my garage.

Better late than never,,,,,,,,,,,,,,,,,,,,,,,,,,,

[Pac-man]

The first year Z was rated at 385hp. From then on, a few things were changed, intake,etc, and the Z rated 405hp. Both ratings were at the crank so you need to adjust for drivetrain loss.

[DRTH VTR]

Welcome to the CAC.

I think this is essentially right-

In 1997, the only Corvette was the targa roof coupe.
In 1998, the convertible was added.
in 1999 (and 2000), the fixed roof coupe was offered.
in 2001, the fixed roof coupe got the LS6 engine and other goodies, and became the Z06. It was rated at 385 HP. The fender badges just said "Z06" with no horsepower designation.
in 2002, the HP rating went to 405HP, mostly due to improvements in the valve train. There may have been some exhaust modifications as well- I am not sure. The fender badges now said "Z06 405HP".

That is strange that your car has the 405HP badges. I suspect that someone changed them at some point. My 2002 has the 2000-2001 badges, which are not correct for my car. They were on there when I bought it with 5800 miles. I cannot explain it.

[kruzmisl]

You picked a good one to start! Enjoy the corvette addiction!

[toms94]

First off welcome to CAC! Stick around and your questions will be answered. Yes I would agree kruzmisl, you are starting with a good one.

[CTYANK2]

Originally Posted by rrp

This is my first posting. This site was extremely helpful when choosing my first corvette. I've just purchased a silver 2001 ZO6. What a great car. It has met all my expectations and then some! Thanks for all the great information.

Quick question; Everything I've read states the C5 ZO6 engine produces 385 HP, yet the insignia on the car says 405 HP. How is the 405 HP rating determined? Is that horsepower in relationship to the HP generated after the exhaust or some other factor?

I've wanted a corvette since I was five years old, 49 years later, its in my garage.

Better late than never,,,,,,,,,,,,,,,,,,,,,,,,,,,

For your first Corvette you picked one of the best ever. Good luck with it. Is your car stock? Maybe the prior owner made a few minor changes that he figured added 20hp so he upgraded to the Z06-405hp insigna to reflect the improvements? Or maybe he just wanted it to look faster!

Hmmmm ... I have a new C6 Z06-505hp insigna ... if anyone wants thier C5 to look faster I'll sell it!

[RVN]

Hmmmm ... I have a new C6 Z06-505hp insigna ... if anyone wants thier C5 to look faster I'll sell it!

Who's C6 did you steal those from?

(signed) "I want my C5 to look faster" btw, my trunk emblem is loose and my ZO6 fender badges rattle!

[twiget]

Welcome to the CAC!

Check out the Model Center. There is a lot of great information there about the C5 Z06's.

I remember when the 2001 Z06 came out. Everyone was all excited about it, then the next year the 2002's came out with an extra 20hp. A lot of '01 owners were ticked off at GM for upping the HP so quickly.

Here is a link to a comparison between the 2001 and 2002 LS6 motors.


Jason

[CTYANK2]

Originally Posted by RVN

Who's C6 did you steal those from?

(signed) "I want my C5 to look faster" btw, my trunk emblem is loose and my ZO6 fender badges rattle!

Yea, I couldn't get your emblems off so I left 'em loose.

Actually I ordered a C5 emblem and was sent a C6 emblem - called the company three times and they said they would send the C5 emblem and a postage paid return for the C6 emblem - they never did!

[Hib Halverson]

There were four major differences between the 385hp LS6 (MY01) and the 405hp LS6 (MY02-04)

First, a more radical camshaft with higher lift and a smaller base circle radius. To go with that lighter valves were required. The intakes have hollow stems and the exhausts have sodium filled, hollow stems. Lastly, the valve stems are longer to restore valvetrain geometry after the base circle radius reduction.

Secondly, the exhaust system was changed. The 01s had the same exhaust as base cars. The 02-04s LS6es had a unique mid-section having only two cats and those cats were speical, low-restriction units not used on other C5s.

Third, the MAF has no honey screen and the airbox on the 02-04s is different, having less restriction.

Lastly, there are, undoubtedly, calibration differences between the two engines.

Why did GM introduce the Z06 at 385-hp then raise the power to 405 the next year. As I recall, there were some late-breaking valve train development issues that prevented the 405-horse valve train from reaching production in 2001.

If you want to know more about both versions of the LS6 engine, see:
http://www.idavette.net/hib/ls6/INDEX.HTM
and
http://www.idavette.net/hib/02ls6/index.htm


Fourth,