mph476

iTrader: (7)

what causes valve spring failure on low lift cams... (.525)???

ACDenali

iTrader: (8)

Not letting springs warm up before thrashing on them will cause failure..
Did a spring let go on you?

blkZ28spt

Aftermarket valvesprings are stronger but also more brittle especially when cold.

mph476

iTrader: (7)

i'm debating on doin a cam swap...not goin to name it here...might cause a war...but spring failure is a big concern to me...I want something that will add great gains but little or no maintenance...I don't plan on revving the hell out of it, so I was just wondering what typically causes spring failure...

blkZ28spt

You aren't going to be able to get much of a cam with "little or no maintenence" on the springs. Should be able to get at least 25k miles out of them if you treat them well.......the only way I know of to get a cam/springs that will not need replacing later on (it's not really a big deal to swap the springs if you have the right tools though) is to get a Hotcam or an LS6 and use the LS6 springs. Problem with that is you leave a fair amount of power on the table to a newer/better grind.

Racehead

I always wait for my oil temp guage to come up to at least 130f. or so before i'll rev it over about 3500 rpms. Once it hits 150 or so then the skies the limit

mph476

iTrader: (7)

so there are cams out there that don't require spring changes ever 15k or so

Mirek

Improper valvetrain geometry will result in failure.

Casperws6

don't forget the ASA cam. has nice torque curve

mph476

iTrader: (7)

so the hot cam and asa cam don't require spring changes every so often?

mph476

iTrader: (7)

so the hot cam and asa cam don't require spring changes every so often?

Viper

iTrader: (6)

Anytime time you change the geometry away from stock and up design, you should check the springs at least every 15K on a typical LS1Tech.com cam and I'll say 30K on a hotcam , LS6 or ASA.

In other words if you took the time to change the cam and spend the money, wouldn't you want to protect your investment and check on it once in a while so you don't spend MORE money if it blows up down the line? Sounds logical to me.

ACDenali

iTrader: (8)

They don't, but its a good rule of thumb to keep an eye on them and change them every so often as needed. When you start building motors up expect things to wear out quicker, especially since you will be running it somewhat hard I'm assuming.

black_knight

iTrader: (1)

Spring failure is caused by:

Beating on it before getting up to temp

Lobes with fast ramp rates

Improper installation

Valve float

...to name a few

KALEL

how do you check the seat pressure??

Casperws6

i don't understand why you would want to check the valve springs on the LS6 cam if that's a stock cam that came in the vette. I mean if someone with a stock vette drove the car for 30,000 miles, would he have to check valve springs also even tho he hasn't swapped cams? I mean does the manufacturer suggest changing them ever "X" amount of miles? It's just a question that popped up?

blkZ28spt

This isn't exactly to the point, but valve springs can fatigue over time as well. It's not unheard (or so I hear) to have springs that get "tired" over time even when stock. Given that it wouldn't be a bad idea for this hypothetical vette owner to check his springs once in awhile even if everything was stock. Also I don't know what methods GM uses on installs, etc, but I can only imagine that it's of a higher quality standard than what many of us do in our garage in our spare time.

Tranzor

The reason a stock z06 doesn't have to check the valve springs every 30k miles is that a stock z06 has the LS6 with the proper valvetrain geometry and valves matched to the LS6 cam.

The stock C5 'Vette has an LS1 with the same cam as an LS1 F-body, so if you just add the LS6 cam, you throw off the valvetrain geometry... plus the heavier LS1 valves will put more stress on the stock LS6 valve springs which were designed to be used with the lighter weight LS6 valves.

DavidNJ

I believe you'll find that even stock springs lose stiffness. However, not enough to impair performance within stock specifications. They need to warranty it to 100k or so for emissions purposes. So they design not to exceed those.

They could change that by putting a spring maintenance procedure in scheduled maintenance. And I wouldn't be surprised to see that in the LS7. As many here are aware, Ferrari specs a timing belt change requiring an engine removal every 15k miles.

I believe there are two failure modes here. One is high cycle fatigue. A crack propagates until the spring fails. That is what happens to NASCAR stock cars.

The second is creep, a long term plastic deformation that causes the lose of spring rate (the 30 million or cycles in 30k street miles is well past high cycle fatique limits). This is accelerated by high spring temperature, which is why extreme spring situations use spring oilers. ARE LS1 valve covers with oilers are relatively inexpensive ($475) and clear high ratio rockers. It is a way to extend spring life. I use them on my SBC.

That said, I would just change my springs annually and check my lifter preload/valve lash a little more frequently.

David

P.S.
For reference, the .842 lifter flat tappet cam in my late model is 248/256 with 1.8 and 1.6 rockers respectively. That is about .59 and .52 at the valve (CI Bowties actually lose flow over .6). Yet the the .020 numbers are only 276/284. I wanted to run 1.9s, however my engine builder put his foot down. Maybe next rebuild we will use hollow stem intakes and the 1.9s.