bearcatt

We all read and hear alot of things...

http://www.gmhightechperformance.com...ine/index.html

The '01 base circle reduction did not require a change in dimensions of any other valve train part; however, the 405-horse cam was a different story. "I wasn't comfortable reducing base circle that much," Hicks told us, "without compensating for it somehow, because the position of the plunger within the hydraulic lifter is not optimal any more-you're too high in the lifter.

"There's different ways to correct the geometry. The one we selected to minimize the impact on our manufacturing operations was to increase the length of the valve. The valves in the '02 LS6 are 0.6mm longer than the valves in all other Gen III engines."

With .025 inch more intake lift, the same intake duration at "fifty-up" but a little less duration at lash and the same rev limit; something had to be done to the rest of the valve train to keep it in control at high rpm. While the '02 exhaust lobe doesn't have quite the aggressive profile as the intake, it's still got more lift, so something had to be done there, too. The choices GM made were to decrease valve weight and increase valve spring pressure.

2002 LS6 Engine Valves
Not only are '02 LS6 valves...


"With the higher lift, we needed to reduce the mass of the valvetrain or start getting into a float condition," John Juriga commented. "We went to hollow stem intake and exhaust valves, very similar to what we used in the '96 LT4. We pushed the edge with a state-of-the-art 0.8mm wall thickness-very thin stuff. The exhaust stems are sodium-potassium filled." The '01 intake weighed 99 grams but the '02 weighs only 76. The '01 exhaust weighed 86 grams but the '02 exhaust weighs 63 grams. The exhaust stems are filled with a 78 percent potassium/22 percent sodium mix to help cool the valve. "NaK" is unstable and may spontaneously combust when exposed to air with 50 percent or higher humidity. Do not cut open or shorten '02 Z06 exhaust valve stems.

As a result of the more aggressive cam, the valve springs were also changed. "Even with the lighter valves," Juriga said, "we still needed better control because we open and close them very fast. The closed loads are the same-400 Newtons (90 lbs.) on the seat-but the open loads increase from 1150N (259 lbs.) to 1310N (294 lbs.) for both springs."

A bigger cam, lighter valves, stiffer springs-so goes the ruthless pursuit of power. And what's this new camshaft and valve train stuff worth by itself? Jim Hicks: "You can do a direct A/B comparison and there's an easy 8-10 hp there, whether you change the back pressure or not. There are other changes in the '02 package-exhaust system and induction system-which increase the power more. The overall power increased about 20 hp and the cam was half of it. Again, that's because it's a short-duration design with low overlap so it's not really affected that much by back pressure.



.

bearcatt

Good choice.


.

mchicia1

Thanks .

I used to be obsessed with max HP and would choose my parts accordingly.

But theres nothing wrong at all with 400 rwhp and stock idle/mpg/drivability/longevity! The beauty of having a very light car.

bearcatt

I hear you, I've been there.

I'm very happy with my pretty much stock 2004 Z06. I like how light weight it is too.

The only thing I've done is install hardened pushrods, new LS6 yellow springs-retainer-keepers, Harlen-Sharp trunion upgrades and maintaince.

The only other thing I plan on doing possibly is a bigger radiator, oil cooler and maybe high output fans to bring the temps down a bit. I know I could program the fans to kick on at a lower temp but I don't want my fans running all the time.



.

mchicia1

Yup, the c5z is a stout car already. My dad has one and its just as fast as my FRC. Those gear ratios help out a lot. We did the same thing on his car and got rid of the silver springs for the yellows as well. Good preventative step IMO.

I was in the market for a c5z before I got my FRC, but with my cam/head install experience, I opted for the much cheaper FRC since I knew I would be modding it anyway. Goal from day one was efficiency/reliability over power, so I am sticking to my guns. I was initially going to do just heads only and stay that way, but my year ls1 cam just effing sucks, so I have to swap it now to hit my power goal.

One thing I realized...you always get used to the power, no matter how much. But you NEVER get used to your car NOT leaving you on the side of the road . That feeling knowing you will get 30 mpg and can drive across the country with no issues never gets old.

bearcatt

That's weird that your Dad's Z06 had silver springs, so did mine with three orange strips.

The modification path you're taking seems to be one that will give you the best of both worlds in terms of power and reliablilty.

Once in a while I like to take road trips, so reliablilty is important.
LOL, getting stuck on the roadside is not something I want to get use to.

Eric D

The spring in the picture above would be the LS6 (2001) spring only. Single spring part number is 12565117.

As stated in my Original Post, the current NEW springs are full yellow and a much better replacement spring compared to the ones it replaces.

mchicia1

Unfortunately, with my last GTO, which made 460, I got both used to the power and sitting stuck on the roadside.

This was all last summer....


1) First the oil pump went (stuck relief valve)
2) Then the clutch went
3) Then the rearend exploded at the track (ok not the cars fault)
4) Then the lifters went and put debris through the motor and took out the cam bearings and the cam.

NOT FUN. I ended up just cutting my losses and sold it to a friend as is then bought my frc. So, that car jaded me a little bit in terms of modding cars to the extreme levels. The lifters going was the worst obviously...which is one of the reasons the first thing I did on the FRC was swap to ls7's and the good ls2 trays.

That gto was perfectly fine (just slow) with boltons only. Going with big *** cams just takes it toll on the valvetrain overtime (not just your springs).

The Wrench

To get factory-engineering answers to all the questions about the various LS1-LS6 valvetrains, just Google "The Ruthless Pursuit of Power - the Sequel" by Hib Halverson. Really informative reading about the development of the '02 LS6.
If I remember correctly, there was advice that using the '02 cam and springs with the heaver valves would lead to stress if the rev limit was not reduced to below 6300 or so.

DG

bearcatt

(sigh)

12499224 is the new replacement part number.

I can promise you that they no longer make the yellow springs.
The new yellow springs are now painted blue with the newer part number.

I searched every vendor that sells GM parts on and off of the forum. Many of the pictures on various websites show yellow springs. Even vendors on this website will send you the blue springs to replace your old yellow springs.

I ended up buying a new set of yellow springs from a member on LS1tech otherwise I would have used an aftermarket spring.

If you find a brand new set of yellow springs they will be left over stock.



.

bearcatt

Man, I'm sorry to hear about all that. What a bummer last summer.







.

bearcatt

Like the link I posted earlier ?
http://www.gmhightechperformance.com...ine/index.html


By the way vettenutts is a mechanical engineer by trade and he knows his stuff.

Here's an example...
http://forums.corvetteforum.com/c5-t...e-pattern.html



.

The Wrench

Yeah that's the link - sorry for redundancy.

dG

bearcatt

It's all good, it a great article.

baxsom

I never run that high anyway so a set of .025 longer pushrods should allow my 01 Z06 heads, 02 Z06 cam, and yellow springs to work.

Eric D

For what it's worth, I stand corrected on the color. I spoke with the engineer in charge of small block valve springs this morning. He confirmed the current replacement springs as you pointed out are blue. I was using the GM EPC which I believe needs to be updated. Later today I will have a list of most current part numbers and colors of the springs that I will post.

lucky131969

That will be very helpful........and find out about that balancer

voda1

The 12499224 number is a 'set' of 16 springs from GM Performance Parts.

12565117 is 2001 LS6 spring - discontinued.

12586484 is the 'individual' 2002-2004 LS6 replacement spring from GM Parts. It has been replaced by number 12625033. Can't comment on the color.

Eric D

I can comment on the color for 12625033, it is Blue.