Var

iTrader: (1)

I'm going to be buying the FM-11 cam( 228/230 576/595 112LSA and apparantly has an aggressive ramp rate ) for my 2001 Z06 and i have a few question. There is a similar thread made today reguarding the F13 and people said that that the 918's will be fine and others said go 921 duals for safety. Nobody said anything about spring harmonics..nobody asked how high the car is going to rev, or how often the owner is willing to change his valvsprings. I read this link but the numbers do not apply to me.

I would like to include more factors into my questions.

First off my vette is my daily driver, so i could easily put 2-3k miles on it in a month. I would like to have my valvesprings last the longest they possibly can before i have to change them, or even check them.

I will be setting the rev limit @ 6800rpm once tuned. I do not drag race, but i go for spirited mountains drives @ sustained high rpm and sometimes to a road course.

1--If your choices were between the 918 and the 921 duals, which would you choose and *WHY*. Also assume that they cost the same so price wont be a factor.

2--Will either spring last longer that the other?

3--Will either spring be completely ok to 6800rpm?(assuming the use of titanium retainers and chromemoly pushrods)

4--Are both these springs drop-in without having to modify the spring seats?

5--Does either spring have a longer warm-up time than the other before you can rev to a certain rpm?


any other random info you have OR suggestion for even a different valve spring is appreciated as long as you can back it up with reasoning.

SouthFL.02.SS

1--If your choices were between the 918 and the 921 duals, which would you choose and *WHY*. Also assume that they cost the same so price wont be a factor.
I'd go with Patriot Gold Duals or PRC duals.
2--Will either spring last longer that the other?
Tough to say.
3--Will either spring be completely ok to 6800rpm?(assuming the use of titanium retainers and chromemoly pushrods)
Yes.
4--Are both these springs drop-in without having to modify the spring seats?
Yes.
5--Does either spring have a longer warm-up time than the other before you can rev to a certain rpm?
General common sense applies. No real precationary procedures.

Var

iTrader: (1)

why would you go with the Patriot Duals or the PRC duals over the COmp duals?

99BackNBlackZ28

iTrader: (5)

Futrals cams do not use agressive ramp rates (compared to comp XE-R, etc).

LSUxBlake

iTrader: (3)

Saying theyre not agressive compared to XE-R lobes doesn't mean they're not agressive, because they are.

I am running Crane Duals with my F11 by the way.

SouthFL.02.SS

Comp 921 is a hell of a spring. But, for the money, I'd get a Patriot Gold or PRC dual which is damn good also, at a savings. I'd spend the money on 921's if I were running a huge cam. Just a personal preference. No scientific data to back up my argument.
I'd use duals either way, though the 918's are up to the task.

vettenuts

iTrader: (4)

1--If your choices were between the 918 and the 921 duals, which would you choose and *WHY*. Also assume that they cost the same so price wont be a factor.

I think you need to examine your spirited canyon driving to answer this one. First, if you are truly driving sustained high RPM, you need a good timing chain and I would also get the chain damper as well since that is what it is designed for. I went with the Katech chain (JWIS). Second, call Comp and get the harmonics on each of these springs. All springs have harmonic frequencies. On the dyno and when accelerating hard, you pass right through them. Most people aren't even aware they exist. However, if you are going to sustain a high RPM, then this becomes more critical. With only these two to choose from, I would go 921 but am not sure about how well the lifters will stand up to the 921's and sustained high RPM running. But based on the spring designs, I would hazard to estimate that the 918's have lower harmonics then the 921's, but I don't have any specific numbers on either.

2--Will either spring last longer that the other?

I would guess the 921's would last better just due to their design.

3--Will either spring be completely ok to 6800rpm?(assuming the use of titanium retainers and chromemoly pushrods)

4--Are both these springs drop-in without having to modify the spring seats?

Yes.

5--Does either spring have a longer warm-up time than the other before you can rev to a certain rpm?

With any aftermarket spring, I usually wait until my oil is 160 before going above 2,000 RPM and then 180 degrees before I drive it hard. Not sure there are any set "rules" on this, but I feel more comfortable doing this and it really isn't any major inconvenience to do so.

SouthFL.02.SS

From JRP's sticky:


1. Comp 918’s: A few years back they had some problems with non-blue stripe springs breaking but they have rectified the problem. The beehive design is also a superior setup due to there light weight and harmonics.. Your stock steel retainers can be reused with the 918’s but titanium retainers are recommended for lightening up the valvetrain and for strength.

Outside Diameter (O.D.): 1.290"/1.060"
Inside Diameter (I.D.): .885"/.656"
Installed Pressure: 130 lbs @ 1.800"
Open Pressure: 318 lbs @ 1.200''
Coil Bind: 1.085"
Maximum Lift: 0.625"
Rate (lbs/in): 313 lbs/in

4. Comp 921’s: Also a dual spring like the Cranes above and come as a kit with everything you need for installation, rated for up to .650 lift

O.D: 1.300
I.D: .870 (outer spring)
I.D: .655 (inner spring)
135 LBS @ 1.770
400 LBS @ 1.220
COIL BIND @ 1.040
MAX LIFT .650


5. Patriot Gold Duals: See Crane and 921’s. The PP Golds come on all PP heads. PP are the only genIII spring setup to use the super 7 10* locks.

O.D 1.29
135lbs @ 1.800
385lbs open
coil bind @ 1.08
.650 lift

My Personal Indepedently tested PP golds:

seat: 143 lbs @ 1.800
open: 363 @ 1.200
coil bind: 1.060
Clearance: .140
spring rate: 367


6. PRC Dual Spring Kit: Kit comes with Dual springs, tit. retainers (using stock locks), seats, valve stem seals. good for up to .660 lift

seat : 140lbs
open: 390lbs
install : 1.800
coil bind: 1.07
1.290 O.D.
max lift : .660
matl : super pure chrome silicone

ninobrn99

iTrader: (8)

i personally was running the prc golds with my f10 and will reuse them with my f13 on the way the 921's do in fact have a thicker spring all together compared to the prc/patriots, but for the f11, any of these will suit your needs. We go with duals for an added piece of mind...besides, i think it comes out cheaper than getting new 918's and new tit. retainers...i think...

Var

iTrader: (1)

Ok so the issues of concern are

1-spring harmonics
2-lifter wear

Vettenuts..according to the link i posted above, the beehive design has a higher natural frequency than a dual spring of the same spring rate, allowing the beehive to rev about a thousand rpm's higher than the dual before harmonics become an issue. But since i want to set the rev limit @ 6800, i dont know if it will even be an issue. I will contact Comp Cams and ask them about it.

As far as stock lifters go, i've heard them to be pretty strong. What do you guys think about the retrofitted stock ones? It's in the CAM sticky (it's from Nasty Nate)

I'm gonna leave my lifters stock for now. 44k miles on them on an LS6. I think they should be ok.


SouthFL.02.SS--Let's say you could get either kit for free. You're not ever gonna change your cam from a F11. Which spring kit would you choose to compliment the cam? Would it still be the PRC's?

ninobrn99

iTrader: (8)

you could also call Allan or Blake (already posted in here) at FMS and ask them what they think. Many many people are running the that cam as well as bigger ones with duals with no harmonic issues. not really something you need to worry about for 2 reasons, you shouldnt need to take that cam that high, 2. the lift isnt too excessive to cause any issues. Just my opinion.
Nino

Var

iTrader: (1)

Ok can you elaborate on your opinion about the redline. Most dyno graphs i've seen for the F11 112LSA peak around 6500-ish and dont drop off after peak, so you can rev it a couple hundred past peak with no problem.

here's 2

https://ls1tech.com/forums/attachmen...chmentid=38492

https://ls1tech.com/forums/attachmen...achmentid=7373

looks like they shutdown before the cam dropped in power

another link

https://ls1tech.com/forums/showthrea...light=f11+dyno

and another

https://ls1tech.com/forums/showthrea...light=f11+dyno

SouthFL.02.SS

I'd still go with the PRC or Patriot Gold Duals. They strike a midground between the 918's and the 921's... Call Comp and Futral for their opinions. Even better, ask LG, as they have extensive Roadrace program.