Go PACs for sure. And while you're in there change to some better push rods too. 
LS6 Valve Spring Info?
Thread Starter
Burning Brakes
Joined: Feb 2006
Posts: 1,085
Likes: 3
From: Ottawa Ontario, Canada
LS6 Valve Spring Info?
Hi all, I broke a valve spring in my '02Z in the fall - got lucky and just had to change one spring - but I'm now replacing all 16 as a precaution.
What are the specs for the stock LS6 springs?
I'd like to put an aftermarket spring in but I want to put the WEAKEST possible spring in there as to not overtax the rest of the OEM valvetrain (upgrading to stronger springs is pointless with a stock cam and an otherwise stock engine...)
As far as I can tell the Comp 918's are popular, any other "weak" spring upgrades I should be aware of?
Thanks!
P.S. I don't want this to turn into a "what spring is best" thead.
What are the specs for the stock LS6 springs?
I'd like to put an aftermarket spring in but I want to put the WEAKEST possible spring in there as to not overtax the rest of the OEM valvetrain (upgrading to stronger springs is pointless with a stock cam and an otherwise stock engine...)
As far as I can tell the Comp 918's are popular, any other "weak" spring upgrades I should be aware of?
Thanks!
P.S. I don't want this to turn into a "what spring is best" thead.
Drifting
Joined: Mar 2002
Posts: 1,298
Likes: 12
From: Salt Lake City UT
Springs
Depends on what cam you are running.
If you have the stock cam or .550 lift or less for the cost it is hard to beat the stock LS6 springs (yellow). I run them in my race engine ( low lift cam) and just change them every season. I have never broken one or had other issues (i.e. weakening and loosing rpm's).
There are lots of good single beehive springs out there. The 918's have had some issues in the past but hopefully have resolved those issues.
You can generally stay with a single beehive spring up to .575/.600 lift.
If you have the stock cam or .550 lift or less for the cost it is hard to beat the stock LS6 springs (yellow). I run them in my race engine ( low lift cam) and just change them every season. I have never broken one or had other issues (i.e. weakening and loosing rpm's).
There are lots of good single beehive springs out there. The 918's have had some issues in the past but hopefully have resolved those issues.
You can generally stay with a single beehive spring up to .575/.600 lift.
Safety Car
Joined: Jul 2004
Posts: 3,904
Likes: 28
From: Vancouver Washington
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Weak is really not the best term.
the PROPER springs for the cam lift may be more appropriate.
I use comp 918s with a 581 lift cam. ( never had an issue with 918s )
behive springs with or for cam lift up to .600 and you will be fine
the PROPER springs for the cam lift may be more appropriate.
I use comp 918s with a 581 lift cam. ( never had an issue with 918s )
behive springs with or for cam lift up to .600 and you will be fine
Thread Starter
Burning Brakes
Joined: Feb 2006
Posts: 1,085
Likes: 3
From: Ottawa Ontario, Canada
Agreed... I want to use the SOFTEST springs possible that are as strong or stronger than the stock LS6 springs.
The proper springs for the stock cam are the stock LS6 springs.
What is the closed and open seat force ("pressure") of a stock LS6 valve spring? Searching is getting me nowhere...
The proper springs for the stock cam are the stock LS6 springs.
What is the closed and open seat force ("pressure") of a stock LS6 valve spring? Searching is getting me nowhere...
Burning Brakes
Joined: May 2008
Posts: 1,147
Likes: 1
From: Mohegan Lake New York
stock LS6 spring is 90lbs closed @1.8" open 294 lbs @1.25" comp cams makes a beehive spring that is direct replacement but is triple the price of stock ls6 springs and has a tad more seat pressure 105 lbs@1.8 installed height (SCOOGIN-DICKEY) $56 VS $155 I'm gonna replace my stock springs on my 85k stock Z/06 with GM SPRINGS I will be replacing the keepers also.Keepers fail when they have a lot of time on them so replacement is recommended they are also inexpensive.I consider valve springs "wear" items as you don't know when they start to get weak and either bounce on the seat or start to "float" (not good) as the only indication is the car starts to slow down but sometimes its so gradual you don't notice.I think that probably most of the broken springs did not break cause they were old /worn out but as a result of losing their tension and floating (not following the contures of the cam) and while floating come in contact with the piston
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Former Vendor
Joined: Jan 2007
Posts: 1,584
Likes: 17
From: Lubbock Tx
I would use either the PAC1218 or PAC1518, we stock both of them and they are great for what you want. The spring pressures are slightly higher than stock but not at all something to worry about.
If you want cheaper, use the 1218, if you are willing to pay another $50 for longer life and even less worry, get the 1518 as they are nitrided. The 1518 is good to .650 lift, but that's irrelevant as the pressures are the same as the 1218
If you want cheaper, use the 1218, if you are willing to pay another $50 for longer life and even less worry, get the 1518 as they are nitrided. The 1518 is good to .650 lift, but that's irrelevant as the pressures are the same as the 1218
Last edited by SDPC; Apr 22, 2010 at 11:42 AM.
Advanced
Joined: Feb 2007
Posts: 52
Likes: 0
From: San Jose California
I got the PAC1218's, but you should look into getting the PAC1215's as they have less pressure. I can't remember the exact numbers, but I would have bought them if they hadn't been out of stock at the time I was buying.
Thread Starter
Burning Brakes
Joined: Feb 2006
Posts: 1,085
Likes: 3
From: Ottawa Ontario, Canada
If K RIPPER is right about the stock LS6 springs ("90lbs closed @1.8" open 294 lbs @1.25"), then I have a question about the 1215's on the LS6 cam...
PAC claims 293lbs @ .600" lift (1.200" height), so at the lesser lift as reported by the stock LS6 spring measurement (.550" lift or 1.250" height) the PAC 1215 would only have about 277lbs of open force.
If the GM spring is rated at 294 that would make me a bit nervous... I doubt GM put much "extra" stiffness into their valve springs, rather, I bet they did a PILE of testing to get them just above the minimum requirements for the cam profile. Looks like the 1215 may have been conceived as an LS1 spring replacement, not an LS6 spring raplacement.
On that same note, the open force on the stock LS6 cam for the 1218 and 1518 would be about 302lbs, only 8lbs higher than the stock springs. Looks like PAC has designed a spring that's taller than the LS6 spring with a lower K value.
This looks like a no-brainer replacement... 1218 for stock/budget minded and 1518 for long life/worry free/upgradeability. For $65 extra from SDPC the 1518 looks like the way to go.
Last edited by Blue Angel; May 3, 2010 at 12:38 PM.
Tech Contributor
Joined: May 2008
Posts: 2,843
Likes: 16
From: Howell Michigan
St. Jude Donor '09-'10-'11
If it were my car I would go with the new LS6 springs. They were improved in 2004. The old part # was 12565313 and the newer replacement is part# 12586484. The spring rate is about 60Nm. 
Former Vendor
Joined: Jan 2007
Posts: 1,584
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From: Lubbock Tx
I still support upgrading to an aftermarket spring, however.
Tech Contributor
Joined: May 2008
Posts: 2,843
Likes: 16
From: Howell Michigan
St. Jude Donor '09-'10-'11
That's the part number for an individual spring. $9 each (approx) x 16 = $144. A whole set from GM under the kit part number of 12499224 is $56.95. If you want to stay with stock LS6 springs, that's the part number you'll want.
I still support upgrading to an aftermarket spring, however.
I still support upgrading to an aftermarket spring, however.
Why would go with aftermarker over the stock spring?
Race Director
Joined: Oct 2002
Posts: 16,477
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
Burning Brakes
Joined: Jan 2008
Posts: 986
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From: Galaxy Traveler
Specs in the manual I have reads this for the LS6:
Valve Springs - Valve Spring Free Length 53.4 mm - 2.1 in
Valve Springs - Valve Spring Installed Height 45.75 mm - 1.8 in
Valve Springs - Valve Spring Load - Closed 400 N at 45.75 mm - 90 lb at 1.8 in
Valve Springs - Valve Spring Load- Open 1310 N at 31.75 mm - 294 lb at 1.25 in
Valve Springs - Valve Spring Free Length 53.4 mm - 2.1 in
Valve Springs - Valve Spring Installed Height 45.75 mm - 1.8 in
Valve Springs - Valve Spring Load - Closed 400 N at 45.75 mm - 90 lb at 1.8 in
Valve Springs - Valve Spring Load- Open 1310 N at 31.75 mm - 294 lb at 1.25 in
Thread Starter
Burning Brakes
Joined: Feb 2006
Posts: 1,085
Likes: 3
From: Ottawa Ontario, Canada
Thanks for all the help and great info, guys/gals! This forum is what makes this car so practical to own - I can't imagine having to pay and trust someone else to do all this for me... 
Former Vendor
Joined: Jan 2007
Posts: 1,584
Likes: 17
From: Lubbock Tx
Tech Contributor
Joined: May 2008
Posts: 2,843
Likes: 16
From: Howell Michigan
St. Jude Donor '09-'10-'11