Valve Spring Life vs. Lift
05-19-2006, 02:45 AM
#1
Staging Lane
Thread Starter
iTrader: (1)
Join Date: Feb 2005
Location: Morgantown, WV
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Valve Spring Life vs. Lift I understand there are many variables affecting valve spring life on the LS1 with aftermarket Cam installations. Just focusing on lift, at what point does lift start to compromise spring life >.560? >.570? >.580? Is there a number to stay below to avoid annual valve spring changes? I am installing AFR Heads milled to 11:1 with Comp 921 Springs and am specing out a cam for long valve trane life.
05-19-2006, 07:34 AM
#2
TECH Enthusiast
Join Date: May 2005
Location: Blairsville, GA
Posts: 555
Likes: 0
Received 0 Likes
on
0 Posts
I wouls imagine that so long as you stay within the specified range that Comp gives for the 921s, you'll be fine. That being said, pay attention to what cam lobe you run... XERs and LSKs are AGGRESSIVE, meaning they open the valve nearly instantly. While this is good for power production, it's bad for springs. If you go with an aggressive cam lobe, I'd suggest you get lightweight retainers/locks(titanium), adjustable roller rockers, and shim your springs to .050" from coil bind when open. While it's more stressful on the springs, it'll keep them from bouncing due to lower spring pressures.
If you haven't got your 921s yet, I'd strongly suggest researching several different springs. If you do have them, there's a lot of experts on here who can enlighten you on where reliability becomes questionable.
If you haven't got your 921s yet, I'd strongly suggest researching several different springs. If you do have them, there's a lot of experts on here who can enlighten you on where reliability becomes questionable.
05-19-2006, 01:00 PM
#3
TECH Fanatic
iTrader: (4)
Join Date: May 2002
Location: Fairview Heights Illinois
Posts: 1,851
Likes: 0
Received 0 Likes
on
0 Posts
I've seen comp 918's go for well over a year without a failure running .630" lift.
The install height on these 918's was increased to 1.895" which reduces the pressure and stress. They are not coming as close to bind as most springs out there. The increased install height was achieved by machining the spring pockets deeper, and replacing the stock spring-seats with thin flat steel shims. It's also on a cool running engine with a LPE2-3 camshaft. The lightweight Z06 valves were used so less spring pressure was needed for valve control.
The install height on these 918's was increased to 1.895" which reduces the pressure and stress. They are not coming as close to bind as most springs out there. The increased install height was achieved by machining the spring pockets deeper, and replacing the stock spring-seats with thin flat steel shims. It's also on a cool running engine with a LPE2-3 camshaft. The lightweight Z06 valves were used so less spring pressure was needed for valve control.
05-20-2006, 06:18 AM
#4
The gradual loss of pressure is a function of stress and temperature. For a specific spring, greater lift at the same installed height, creates greater pressure and also raises the spring temperature.
Things like isotropic polishing (REM polishing), coating, and valve spring oilers reduce spring temperature. Higher quality materials are also less subject (less not none) to the gradual pressure loss for a specific application.
While an LSK may seem radical compared to an XER, and XER radical compared to an XE, they are all mild compared to many solid rollers. And solid flat tappet designs are more radical off the seat.
Things like isotropic polishing (REM polishing), coating, and valve spring oilers reduce spring temperature. Higher quality materials are also less subject (less not none) to the gradual pressure loss for a specific application.
While an LSK may seem radical compared to an XER, and XER radical compared to an XE, they are all mild compared to many solid rollers. And solid flat tappet designs are more radical off the seat.
05-21-2006, 01:35 PM
#5
Originally Posted by DavidNJ
While an LSK may seem radical compared to an XER, and XER radical compared to an XE, they are all mild compared to many solid rollers. And solid flat tappet designs are more radical off the seat.
Bret
05-21-2006, 02:40 PM
#6
TECH Fanatic
I dont know if there is a set number for lift where valvespring life comes into question. There have been quite a few valvespring failures on stock LS6 motors (lift ~.551). I plan to change my valvesprings when my car is out of warrenty. I would say to be safe for 100K miles stay around .525, you could go with the stock '02+ LS6 camshaft and stock LS6 springs and probably be good for 50K miles inbetween valvespring swaps without a problem. Most of the aftermarket grind cams have very aggressive ramp rates (comp XE, XE-R, and LSk~ getting more aggressive respectively) all have more aggressive ramps than the stock LS6 camshaft. I hope some of this helps. One good thing about the duals you are thinking of going with is that you will most likely feel the loss in power at the upper rpms if you break a valvespring and you will have the backup to get you through till the swap. Hope some of this helps.
05-21-2006, 02:45 PM
#7
Staging Lane
Thread Starter
iTrader: (1)
Join Date: Feb 2005
Location: Morgantown, WV
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by niphilli
I dont know if there is a set number for lift where valvespring life comes into question. There have been quite a few valvespring failures on stock LS6 motors (lift ~.551). I plan to change my valvesprings when my car is out of warrenty. I would say to be safe for 100K miles stay around .525, you could go with the stock '02+ LS6 camshaft and stock LS6 springs and probably be good for 50K miles inbetween valvespring swaps without a problem. Most of the aftermarket grind cams have very aggressive ramp rates (comp XE, XE-R, and LSk~ getting more aggressive respectively) all have more aggressive ramps than the stock LS6 camshaft. I hope some of this helps. One good thing about the duals you are thinking of going with is that you will most likely feel the loss in power at the upper rpms if you break a valvespring and you will have the backup to get you through till the swap. Hope some of this helps.
Trending Topics
05-22-2006, 02:21 PM
#9
It is hard to upgrade from the comp 921 springs...the info on shiming in the above post is true..I have 25,000 miles on the TSP platnum duals on a cam with .600 lift and they are performing perfectly. There is a lot of 
out here about chainging your springs at 15,000 miles..you can do it if you like to change springs and spend money..If you want to ask someone about spring life try Geoff at Thunder
Racing or Jason or John at Texas Speed. They can share some words of wisdom on the subject with you. I am installing a custom cam with LSX lobes and I plan on running the comp 921s for a long time..
out here about chainging your springs at 15,000 miles..you can do it if you like to change springs and spend money..If you want to ask someone about spring life try Geoff at Thunder Racing or Jason or John at Texas Speed. They can share some words of wisdom on the subject with you. I am installing a custom cam with LSX lobes and I plan on running the comp 921s for a long time..
05-23-2006, 08:07 AM
#10
The 921's are certainly priced as a premium spring. However, they are designed for the small 1.3" OD and don't have any of the surface treatments (isotropic finishing, coatings) that reduce temperature.
The way I was taught to determine spring replacement time is by checking the seat pressure. Numerous manufacturers make a tool for this.
In is my understanding that the failure method for springs was creep, which is a gradual deformation under stress at elevated temperatures. All valve springs, even in production engines, would be subject to it. However, running at lower stresses and with lower performance demands, their springs have a long service life.
One way to reduce this is using valve spring oilers to cool the springs. However, it seems few LS1s do this.
The way I was taught to determine spring replacement time is by checking the seat pressure. Numerous manufacturers make a tool for this.
In is my understanding that the failure method for springs was creep, which is a gradual deformation under stress at elevated temperatures. All valve springs, even in production engines, would be subject to it. However, running at lower stresses and with lower performance demands, their springs have a long service life.
One way to reduce this is using valve spring oilers to cool the springs. However, it seems few LS1s do this.
05-23-2006, 09:34 AM
#12
Staging Lane
Join Date: Oct 2004
Location: AUSTIN, TEXAS
Posts: 70
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by 1fastWS6
According to one of the well known cam experts out there, Jay Allen of Cam Innovations, cam lift doesn't kill springs. He said that a mis-matched lobe ramp rate and spring rate are what kills springs.
05-23-2006, 10:00 AM
#13
TECH Fanatic
Originally Posted by M2SPEED
So what is the formula for figuring the correct spring for ramp rate?
There are so many "springs" in a pushrod valvetrain that software that approximates it is fairly new and very pricey. Any new application still needs to be tested. Here's some nice software.
http://www.profblairandassociates.co...ucts_Main.html
In decreasing order of relative spring rates:
1) valve spring
2) pushrod
3) rocker arm
4) rocker stud
5)> cam torsional rate, retainer, valve stem, etc.
05-23-2006, 11:23 AM
#14
TECH Fanatic
iTrader: (14)
Join Date: Dec 2003
Location: Salisbury,MD
Posts: 1,729
Likes: 0
Received 0 Likes
on
0 Posts
There is a crazy amount of varaibles involved in determining spring life. The spintron is an excellent tool but even it doesn't account for the heat and forces exerted by the moving gases in the motor during running conditions. My suggestion would be spend $75 for a moroso valve spring checker and pull your valve covers off once in a while to verrify seat pressure (I'm not sure if it works on stock rocker arms, but I know it works on my jesel pro series). Once it's dropped by a certain percentage over when they were first installed time to swap
And some of us do use spring oilers
And some of us do use spring oilers
05-25-2006, 07:58 AM
#16
Staging Lane
Thread Starter
iTrader: (1)
Join Date: Feb 2005
Location: Morgantown, WV
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by slt200mph
It is hard to upgrade from the comp 921 springs...the info on shiming in the above post is true..I have 25,000 miles on the TSP platnum duals on a cam with .600 lift and they are performing perfectly. There is a lot of out here about chainging your springs at 15,000 miles..you can do it if you like to change springs and spend money..If you want to ask someone about spring life try Geoff at Thunder
Racing or Jason or John at Texas Speed. They can share some words of wisdom on the subject with you. I am installing a custom cam with LSX lobes and I plan on running the comp 921s for a long time..
out here about chainging your springs at 15,000 miles..you can do it if you like to change springs and spend money..If you want to ask someone about spring life try Geoff at Thunder Racing or Jason or John at Texas Speed. They can share some words of wisdom on the subject with you. I am installing a custom cam with LSX lobes and I plan on running the comp 921s for a long time..
05-28-2006, 11:29 PM
#17
Staging Lane
Join Date: Oct 2004
Location: AUSTIN, TEXAS
Posts: 70
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by SStrokerAce
Not really, there are some aggressive lobes like the TK lobes that are much easier over the nose than LSK or XER lobes... FWIW those two lobes have a similar nose to them.
Bret
Bret
05-29-2006, 08:36 AM
#18
TECH Fanatic
iTrader: (14)
Join Date: Dec 2003
Location: Salisbury,MD
Posts: 1,729
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by AJay
Can someone briefly explain the shimming procedure or direct me to a link that has this info? Thanks
https://ls1tech.com/forums/generation-iii-internal-engine/451232-comp-xfi-lobes.html
Look at post #9
Hope that helps
05-29-2006, 11:04 AM
#19
05-29-2006, 03:17 PM
#20
TECH Fanatic
iTrader: (14)
Join Date: Dec 2003
Location: Salisbury,MD
Posts: 1,729
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DavidNJ
You can acctually link directly to a post: https://ls1tech.com/forums/showpost....58&postcount=9
