Grant B

I came from a turbo car (Supra), thinking "Wow, these LS1s can make good power NA. What can break on a stockish NA motor?". Now that I read about some people changing their valve spring every 10k, I am kind of concerned. I plan on doing many open-track events, and generally spend LOTS of time at high RPM whenever possible. The car will eventually be H/C. But the problem is, I am a lazy bastard and don't like doing maintenance or fixing things if I don't have to.

I would like to better understand what causes valve springs to wear out quickly. I haven't been able to find any good threads about this. Looking at the Z06 LS6 cam, its not that much less aggressive than others. We aren't talking about double the lift, or even 20% more lift. Its just got a little less lift, little less duration and a little lower ramp rate and yet GM makes it reliable enough for a stock car with a warrenty.

So what causes valve springs on hot cams to wear out 10x faster than stock? My guesses are:
1) RPM
2) Lift
3) Duration
4) Ramp-rate
5) Spring stiffness? Correct me if I'm wrong, but a stiffer spring will always wear out faster.
6) Spring height? Will a taller spring wear out as fast?
7) Metalurgy and spring design, which I know nothing about. I think we will all agree than OEM parts are generally much higher quality than aftermarket parts.

So, wouldn't we want the softest spring that we could get without float? And lighter valvetrain components to reduce the need for a stiff spring. Some of us aren't going to rev as high as others, so it would make sense that those of us sticking around 6500 rpm max have softer springs than those going to 7000 or above. Is it possible people here are using springs that are too stiff, which is decreasing their service lift? Or am I totally full of ****?

About number 6: Are there any heads with facilities for longer springs? Like AFRs?

I need power from 4500 to 6600 (assuming thats a safe rev limiter, I assumed it was since thats the factory Z06 limit). If valve spring life means I have to live with 450whp instead of 480whp on AFR heads, then so be it.

Thanks for any help,
Grant
'99 Pewter FRC C5

PS: My last car had a directly actuated 4-valve shim-over bucket valvetrain, so if I say something really stupid that doesn't apply to pushrod motors, please don't flame me too badly

Old SStroker

The short answer is "stress" and "frequency". The closer to it's max travel limit you compress the spring, the more stress (psi) the wire sees. You do this with high lift and limited spring length. The higher the rpm, the more the acceleration loads and things like toss which stress the spring. At some stress level (like with OEM engines, even an LS6), the springs will live 100K plus if you keep the revs within OEM limit.

If people are losing springs in 10K on LS engines with reasonable lift and rpm limits (like you propose), they aren't using the correct springs. If you want 4500-6600 power on an otherwise stock LS engine, have a complete valvetrain designed for you including cam, pushrods, springs, retainers, and maybe rockers and even lifters. Your rpm goals are not outrageous, so you should be able to get a system that will increase power and also give you a heck of a lot more than 10K miles, unless most of them are on track. .

I believe Hot Rod had a LS1 spring tech test in the July issue. Very interesting.

Nightclaw

So, how does one know when to change springs? I'm coming up on ~10k on Comp 918 beehives being squeezed by a TR 224/224 561" stick. I also have Ti retainers and chromoly pushrods, with stock rockers and lifters. Is spring replacement a "regular maintenance" thing, or is there a symptom (besides breaking a spring or floating a valve) that's a tip-off that it's time to change springs? My engine sees the high side of 4k on a regular basis, but with stock tuning, it never goes over 6250. Thanks, and sorry if this is a "cam newbie" question.

-Brian

Viper

iTrader: (6)

"So, how does one know when to change springs? I'm coming up on ~10k on Comp 918 beehives being squeezed by a TR 224/224 561" stick. I also have Ti retainers and chromoly pushrods, with stock rockers and lifters. Is spring replacement a "regular maintenance" thing, or is there a symptom (besides breaking a spring or floating a valve) that's a tip-off that it's time to change springs? My engine sees the high side of 4k on a regular basis, but with stock tuning, it never goes over 6250. Thanks, and sorry if this is a "cam newbie" question."

I've got the same question; I'm at close to 15K on Isky 295D's with the same cam. How do you know when?

Also , CStraub has a post out there from January this year or so, about how they put a timing light on the valve springs and were horrified to see the bouncing going on at high RPM; he was working on a better lock/retainer system. FWIW, people are still looking into why the valve springs are only lasting 10-15K.

https://ls1tech.com/forums/generation-iii-internal-engine/147013-any-news-super-7-locks-yet.html

Plan B

Pull a couple out and measure them.

Nightclaw

Ugh. That can't be the only way (and yet it wouldn't surprise me if it is). <sigh> Well, no such thing as a free lunch, I suppose...:p

Let me ask another question. Having a TR224, by today's standards my cam is one of the less radical ones around in terms of lift (.561"). If I made an investment in double springs (or better singles), would I come close to having a maintenance-free valvetrain (ie: last closer to 60-70000 miles instead of 10-15000)? What it boils down to is that I put too many miles on my car to be replacing valve springs every 10-15k miles (that's about 6-7 months of driving for me).

MyLS1Hauls

iTrader: (2)

Good springs are lasting longer 10k. I've got 25k on my 918 blue stripes with an XER cam. They are still going strong. You can't get better single springs for this application than 918s...period. When I port a new set of heads for my car, I'm still going to run 918s. IMO, there is no need for duals with what I'm running. Also, dual springs will not necessarily last longer than singles. It's totally dependent on the characteristics of the spring (take a look at posts from a year ago on REV 1116 duals and breakage). Remember too, RPM plays a role in how fast the valve is opened and closed, so the lower the rpm you drive your car at, the less stress the springs see. Also, I will be measuring my 918s again soon to see how much if any they have lost in the last 10k miles. Last I checked, they were within 10% of their initial rate...but springs always sag a little after the first few heat cycles.

BADFNZ

iTrader: (19)

It also depends on your driving characteristics and valvetrain weight. Someone who does a few WOT blasts a day is going to go through springs more often than someone like me who goes WOT maybe once a week. Also, if you have titanium retainers or lightweight valves, less stress is put on the spring. Also, if the springs are broken-in and heat cycled correctly, they will live a much longer life.

I have over 20k on my Comp 918's but of course I drive like a grandma, have lightweight LS6 valves, and have a rev limit of 6700.

Cstraub

iTrader: (1)

Heat is the biggest killer of valve springs. Impurities in the wire itself get hot and break the wire down. Springs like the PP made from super clean chrome silicone have less of these impurities and because of this reason have better spring life.

Chris

corvet786c

iTrader: (6)

I know this is an older post but would like to add that forced induction applications put a lot of stress on the springs. The stress of the intake valves from boost can wear them down a lot.