Do valve springs need to be changed when cams are upgraded?

[Howieau]

As the title suggests, do the stock valve springs need to be changed when bigger cams are put in? Its just that I have bigger cams than stock in my car done by the previous owner, but Im not sure if he upgraded the valve springs. I had my head in getting reconditioned recently and needed valves replaced cos they were thinning so I gave him replacement valve/springs etc from another head. I didnt think the springs would be an issue, but now im thinking that if he took the ones out of my head and put in the stock ones I gave him off of another head, he might have taken the stronger ones out and put stock ones it.

Im just thinking if valve springs dont need to be upgraded with cams, then the past owner probably didnt put stronger ones in.

[RobertoX]

It depends on the lift that you will be running as to whether the springs will become bound. It also depends on the ramp profile of the cams and the revs you run the engine at as to whether you get valve float.
There are also other factors like the strength of the springs and the stress that they'll see with the new cams.

So it depends on the lift and profile of the cam and the motor that you are putting them in...

[love ke70]

get decent after market ones.
the extra money is worth it if you want it to last, and as the head has to come off to change springs id suggest doing it just for peice of mind.
with all these threads you keep starting you'll end up replacing the entire thing soon

[ed]

decent after market springs??

why???

care to add anything specific other than 'peace of mind'??

you need springs whose natural harmonic freq does not coincide with the operating parameters of your engine, and whose rate and travel match the lobe profile. clearly the oem springs (or whatever was in there) accomodated your obviously not-too-beserk cam profile, and your engine builder would definitely note whether the ones you swapped in went to coil bind when he put bolted it together...

maybe if you were running a motherload of boost, maybe if you have decidedly nasty cams. but otherwise?? peace of mind? with respect to what? oem spring quality is sure to be greater than 90% of aftermarket springs...

broke? fix? aint...

[styler]

only put in stronger one if they are needed, check for binding like mentioned but the main reason to change them is over time they tend to go all over the place with specs and a new set isnt usually very expensive.

[The Real Roadrunner]

i know from experience that 3sgte gen3 springs bounce with 18psi@7800 if that helps.

[EldarO]

isnt engine RPM more of a factor than anything else?

thats the impression i was under, if someone could shed some light for me that would be lovely.

Why is boost a factor?

Elmo.

[ed]

boost will blow the vales open if the spring tension is too low - ie valves wont seal.

engine rpm is a factor but certainly not the only factor

[ed]

threads:

http://www.v-eight.com/tech_forum/viewtopic.php?t=25

and

http://www.v-eight.com/tech_forum/viewtopic.php?t=65

[EldarO]

thanks for the info ed, appreciated!

Elmo.