UstaB-GS549

getting nervous about the valve springs in my 14,000 mile 02 Z06. There have been enough failures reported on 02 cars that I think it's worth switching them out. I don't ever plan on modding the engine and I run 6 or so DE events a year along with a few AX.

I'm leaning toward just getting a new set of springs from GM because as far as I know, they are designed to last the life of the engine.

The Comp 918 springs seem to have a good reputation, but the seat pressure is higher, they are more expensive and they have had failures in the past too.

I would be interested in opinions from guys who either race or have a lot of miles on either type of spring.

sothpaw2

This is a difficult issue to deal with. I have done some research here on the failures.

It seems that most of the failures don't result in a dropped valve and so almost no one blows the engine. Then again, a lot of the time they are not on track at high rpm at the time.

There isn't any difference in an '04 spring or an '02 spring. So to be sure, you would go to the Comp 26918 spring and maybe hardened pushrods as well (I an not sure the pushrods are mandatory).

It seems like most of the cars with failures also have a lot more than 15,000 miles on the car (what I have now on my '02). I don't think of read of one yet below 30,000 miles.

It's going to cost me $400 for labor + the spring cost+any other hardware (?retainers&locks) to do the change, so I am thinking I want to wait on it. This even though I plan on doing 2 HPDEs right away this year.

I haven't had the best experiences with my '93 vette and other cars on doing preventative repairs. On the '93 replaced the Opti and then got a bad one brand new, and then the ignition module went up (?mechanic screwed it up in the assy/dissassy). This time I'm going to take the approach "If it ain't broke don't fix it" at least for a while. If I don't have any other repairs needed then I can do some elective spending next year. Now I want to enjoy the car and worry less.

UstaB-GS549

I can get the stock 02-04 springs for $60 or so, the tool to compress the springs for another $100, and my labor is free.

I know that most guys have had springs fail at fairly low RPM, but even then the valve probably dings up the top of the piston.

The sad part is that I could be replacing perfectly good springs with bad service parts. I guess I could take the approach of replacing the springs every other year (roughly 10,000 miles) and view it as routine maintenance. What are the odds of having a fatigue failure in that amount of time?

96CollectorSport

Here is a valve spring compressor made just for the LSx motors.
It's $199 from SDPC, but looks better than the old crank style.

VetteDrmr

I just did this, and with the Crane compressor (which is what I'm assuming you're referring to), it's a piece of cake. I spent as much time replacing the spark plugs, wires, etc. as I did swapping out the springs, maybe more.

To the best of my knowledge, the "yellow" springs are working just fine. I just replaced my 148K mile springs, so maybe I don't have enough time on them yet. I *do* know I always get the oil temps up over 150 degrees before I let her run.

HTH, and have a good one,
Mike

sothpaw2

I think the odds of a fatigue failure are pretty low at 10,000 miles but also almost equally low at 14,000 miles. I do fatigue analysis for a living. Please keep in mind that the fatigue life curve is plotted on a logarithmic scale--what I mean is that a small difference in stress makes a big diffrenence in life. A 10% difference in stress might mean 2-3 times more life.

Personally, as we are worried about the '02 springs, I can't see changing to the same ones. I would do the 26918 and be done.

davidfarmer

I ran those (stock) springs at 7500rpm with a BIG GM cam with no problems ever. They work great with the the light-sodium valves, although they can't handle heavier aftermarket valves. Just my 2 cents worth.

UstaB-GS549

I guess that's why I'm not really sold on the Comp 918. If the seated spring load is a little higher that the OEM spring, then something else has to be improved for equal life. Sut, suface finish or something. If the knee in the curve is at 10^6 cycles... I wonder how many miles that is?

UstaB-GS549

Good information! Thanks.

sothpaw2

I suspect that the 26918's are not hardened as to be so brittle. They are good to a 0.600" lift so they are supposed to be designed for this loading. Surface finish could be a lot better for the extra money.

My issue with them is more that they come from Comp--not to bash Comp, but they are a performance 1st company. I don't know that they are designing their products to last 100,000 miles. Most of these modded cars aren't built for longevity.

davidfarmer

just throwing some number is, I get around 22 million cycles in 10000 miles. So depending on whether you think fatigue is a problem or not (I don't), then you should definitely give changing some thought. I really don't think fatigue should be an issue in these springs used with a stock cam.

I only studied fatigue briefly in engineering school, but we used 1 million cycles as "infinite". In other words, if you built it so that it would last 1 million cycles, then it should last "forever". Again, 2 or 3 lectures in materials class isn't much background.

TommyBoy72

Not to hijack but should I be proactive on an 01 Z06 with 53k miles? I was considering doing this but the write ups I found never mention if there are access issues to reaching all the valve springs.

VetteDrmr

If you use the Crane valve spring compressor there's no problem with access. It's one of the few high dollar tools that are a true bargain.

As far as being proactive goes, if your engine is stock I don't think you ever need to change them out from a breakage standpoint. I think mine were getting weak and I was seeing some valve float at higher rpms. Can't say for sure since I don't have a dyno, but I figured after 150K miles it was time.

Have a good one,
Mike

TommyBoy72

While normally I would agree with this logic, but a local with less miles suffered a failed valve spring in his 02 Z06. His is completely stock. We both autocross so the car does often see high RPMs. I am just starting to do more research on this as I was under the impression this is pretty uncommon but with the local's failure it at least has me doing the research. I appreciate any advice.

UstaB-GS549

It seems that some 02 Z06's may have a bad batch of valve springs. There have been enough failures that I figure that it would be wise to switch mine out. Especially since they are single springs.

At this point I'm leaning toward just replacing them with stock springs. I just got a reply on the other forum from a guy who just broke a Comp 918 spring. Without modifications to the engine, I can't see any benefit in aftermarket springs.

TommyBoy72

Ah, so the stories are primarily 02s? I hadn't caught on to that until you just said that.

UstaB-GS549

At least that's the impression I have. I normally don't trouble trouble by fixing things that are not broke.

sothpaw2

I have asked here about '01s and not heard of any failures. There was rumored one failure to a non-member's '01, no details.

Very few failures if any on '01's or '04's, documented cases in Z's made in calendar year 2002 ('02's and '03's).

TommyBoy72

Thanks for the info. I spent some $ on the CLB instead although mine has the newer part - just to be a bit safer.