LS6 springs vs. 918's
 

I'm real close to putting in my cam now, and still can't make up my mind on what springs to get. I've done lots of searching on here and still can't decide. The 918's were recommended by the shop that will be doing the swap. I just don't see the benefit of the 918's over the LS6 springs on my small comp (216/220 .525 .532). The 918's seem like overkill. Why would I need more seat pressure than the LS6's provide. The LS6's are good for .600 lift, which is more than enough. I like the idea of going 70,000k+ miles without a worry. Longevity is a concern, and I don't see a performance benefit with the 918's. Any thoughts on this? :confused:

I am interested in the responses to this as well.

918s are much better springs. With the higher ramp rates of the aftermarket cams you will need the better springs. I think Comp Cams recommends the 918 spring for the 216/220 cam.

I don't think the LS6 springs will be good for your application...its about ramp rate not necessarily valve lift.

Comp cam recommends 915 (LS6 replacements) for that cam and 918's as an "Upgrade".
Just make sure you get 02 or newer LS6 springs.

QUOTE: Comp cam recommends 915 (LS6 replacements) for that cam and 918's as an "Upgrade".

What I don't understand is why the 918's would be an "upgrade." I don't see why using a spring that is stiffer than necessary will be beneficial. I"ve heard that you don't want to "over" spring your car either. The price difference between the two isn't much and I do want the best one for my car. But the way I see it is that the LS6 spring will last longer, and the 918 won't show any added benefit. Am I wrong? I'm sure comp has reasons for recommending their own spring.

I think how high your going to spin the engine would make a big difference also the LS6 has a very light valvetrain, don't know what your using? I have this cam on the shelf and will be using 921 springs that I have in the heads already.

Two things I see here:

** The 918 is a beehive design which means there is less reciprocating mass
near the retainer. That helps to control harmonics.

** The seat pressure @ 1.800" install height is 130# for the 918 spring.

I can't see that being overkill for an engine that spins to 6000+ RPM.
Seat pressure IMO is far more important than open height pressure.

The valve must come down in a controlled manner and not bounce.

Just some thoughts to help out.

QUOTE: Like as stated above..it's not always about lift. Ramp rates can be very hard on springs. Stock springs are mare for longevity, not performance. A 918 will last a lot longer on a faster ramp than a stock spring will, plus the valve control and stability will be better.

Yeah, but my comp cam does not have aggressive ramp rates. It's fairly "soft" from what I understand. This cam also only makes power to 6300 rpm. I could see if I was running higher lift or an extreme energy cam, but on my tiny, soft cam are 918's really helpful? What are we looking at with the 918's 30k mi?

I think I answered your question already.
915's are the recommended ones by Comp. (02+ LS6 springs Comp replacements)- So YES 02+ LS6 springs will work fine.

01 LS6 specs 204/211, .525/.525 116lsa
02 LS6 specs 204/218 .551/.541 117.5lsa
Comp 269 specs 216/220, .525/.532 114lsa

QUOTE:I think I answered your question already.
915's are the recommended ones by Comp. (02+ LS6 springs Comp replacements)- So YES 02+ LS6 springs will work fine.

Thanks for your help predator. No offense, but thats not my question. I already know LS6 springs will work "fine." I don't want to go the cheap route, and want to do 918's if they are best. My specific question is: If the 918's are considered an upgrade to the LS6 springs, how so? How can the 918's be better than the LS6 springs on such a small cam, with soft lobes? Is it worth it performance wise, to lose longevity in my situation?

I added to my post.

I ran that cam for around 8K miles on a 98Z with 01 LS6 springs with no issues so the better 02+ LS6 springs should be fine as well.