Forced Induction - Comp 918's on boosted motor

Wondering if 918 comp springs are going to work with an MTI stealth II cam and 15 or so psi of boost. Already have the 918's, not sure if I should sell/trade and upgrade to a better single-spring. Opinions?

I think 918's are a very nice spring for that setup. I've seen a few broken dual springs but never seen a broken 918. Nice cam BTW!!!

Bobby

I ran 918's with stock heads/cam for a while on a ProCharged setup. They worked fine. I think I'd prefer a dual spring when using a larger cam though. The 918's are definitely good for the money.

I hope it works out well for the rear mount. Had trouble spooling the T70 out back with the hotcam and short gears. Need taller gears, and wanted to get rid of the lope... Cops in this area are Nazi's when it comes to that, and will have your car inspected. I read that the 918's were rated at .600 lift, but then I realized yeah, I'm under that, but... under boost won't it hang the valves? I hope the 918's work, def didn't want to go double spring on a street car.

I don't know that there is much of a difference between N/A and F/I springs all other things equal?

I don't know that there is much of a difference between N/A and F/I springs all other things equal?

Well, I'll stick with the 918's and see what happens. With 2.02/1.575" stainless valves and stock retainers, am I going to have a valve float problem up higher in the band? Not sure where the power range under boost is going to be with cam, but just don't want future problems.

well supposedly pple who have used the 918's are commonly pple who upgrade to LS6 parts or pple with nicer aftermarket H/C setups, and i think i remember seeing alot of them revving the crap out of their cars with no valve float...

i think you should be fine with the 918's, like u said they're rated to .600, so keep using em..what are the specs on the stealth cam? just curious

Wondering if 918 comp springs are going to work with an MTI stealth II cam and 15 or so psi of boost. Already have the 918's, not sure if I should sell/trade and upgrade to a better single-spring. Opinions?

The 918's are a lot more spring than most people give them credit for. They were originally rated to .615" lift and then down graded once the 921's came out...most likely a ploy to sell more dual springs.

If shimmed to .050 within coil bind the 918's can handle damn near most cams with up to .620 lift these days. I just wouldn't throw them on a LSK lobe at all, or throw them on a big XE-R lobe without shimming them.

They will work wonderfully with that little cam and you shouldn't have to worry about valve float.

Nate

was never sure but with the TTi street kit, at 15psi, it seemed I was getting valve float at 5500 rpms with the 918s. That was with a '01 z06 cam. I THINK i was because i couldnt trace it down as being an ignition prob but i would suddenly get massive misfires at that rpm. 13 psi and got no misfires. Just my experience which i know doesnt help

I vote for more spring too. I think with 15psi trying to blow the springs open, you will float the valves. JMO

dont know the specs of your cam but the this 222/228 .56whatever XE cam does just fine to 7000rpm @ 14psi with the single springs that came on these darts. They are similar to 918s, I read they are the same spring (made by PSI) as 918s but I'm not sure of that..

Either way they work for me, If I have to toss a 140.00 set of springs in once a year I'll deal with it ;)

Yeah, the stealth 2 is 224/220 @ .050 and .581/.581 lift. I just don't need major problems with the new motor, but also don't want double springs. *Keeps fingers crossed* Hope they work out.

When you mentioned lope, were you referring to the hotcam? How much of a lope do you get out of a hotcam with a rear mount? Doesnt it muffle a lot of it.

I think at 15PSI you'd want to go to a dual spring. I am running CC918's right now at 5PSI with no probs (mods in sig), but the new heads I have to install have duals on them. I'll be upping boost to 8PSI then. I think 15PSI might be a bit too much for the 918's. Just my $0.02.

Yeah, the stealth 2 is 224/220 @ .050 and .581/.581 lift. I just don't need major problems with the new motor, but also don't want double springs. *Keeps fingers crossed* Hope they work out.

Why so against the duals?

When you mentioned lope, were you referring to the hotcam? How much of a lope do you get out of a hotcam with a rear mount? Doesnt it muffle a lot of it.

Well the hotcam isn't giant, but it wasn't really tuned well, so it still surged, especially with the 42# injectors. I had a 3" bullet before the turbo and a 3" downpipe, and it made enough noise for people to notice the car was pretty far from stock, and by that... I mean, not smog legal...

Why so against the duals?

Not really sure, but on my 67, I had so many problems with duals and the solid roller. If I could get a dual spring that will utilize the same height valves without beating the hell out of everything, I would definitely consider it.

I think at 15PSI you'd want to go to a dual spring. I am running CC918's right now at 5PSI with no probs (mods in sig), but the new heads I have to install have duals on them. I'll be upping boost to 8PSI then. I think 15PSI might be a bit too much for the 918's. Just my $0.02.

My car initially had issues with the boost controller and hit 10# and 6500 rpm with the hotcam and z06 springs. Not sure if that makes a difference or not.

I floated 3 valves at 15psi on 918's with a 224/224/112 .567/.567 cam.

I now have a stronger springs but I don't know what they are.

I floated 3 valves at 15psi on 918's with a 224/224/112 .567/.567 cam.

I now have a stronger springs but I don't know what they are.

What kinda R's were you running when they floated?

I would get the Patriot duals. You dont only have to worry about the cam lift, but youre also going to have 15 pSI of air trying to push down the valve too. You have to think of both sides with FI. Im using PP golds with my baby GT2-3. Floating valves is ugly.

I looked into the patriot duals, rated at .650 lift. Do those springs require different retainers? Everywhere Im looking it looks like they're selling it as a kit.

The kit comes with everything needed for the install! Springs, titanium rtetainers, locks and even new valve seals. I got mine from Bynuspeed!

My engine builder had no problems recommending comp 918's for my motor, knowing full well I intend to run 15psi worth of boost.
Before even talking with him, I spoke with several techs with Comp, none of them had anything negative to say either.

Great, I'll have to get rid of my new 918's then, at least I hadn't installed them on the heads yet! They come with the machined spring seats don't they? That's the real reason why I didn't want to go dual is because I'd have to find the spring seats, but hey, if they come with it, more power to em. Never heard of Bynuspeed, how much are they? I found at lmperf (I think) $255 + $18 shipping) for the kit. Hit me up, and hit me up if you need a set of new 918's! LOL Thanks guys!

My bad, yes, they do also come with hardened seats! Its a killer deal fo' sho'! The also work with stock lifters.

My engine builder had no problems recommending comp 918's for my motor, knowing full well I intend to run 15psi worth of boost.
Before even talking with him, I spoke with several techs with Comp, none of them had anything negative to say either.

No offence, but they didnt have anything bad to say when the 918s first came out and all of them broke destroying countless motors. ;)

LOL, I posted my 918's for sale in the sales dept. I plan to run the CC 850-16 rollers, I had heard bad things about the Comp "R" lifters, and it's not an all out racecar, so I don't need morels. Thanks for steering me in the "safe" direction, better safe than sorry.

true that! I ran a set of Comp Rs for about 12k and never had one problem. I think the problems come from too much preload. You have to know how to properly set them up.

No problem on the springs. I always perfer a dual over a single performance spring. You have the extra incase something does go wrong. :cheers: