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?

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

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.

Why so against the duals?

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...

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.

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.

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