I'm running a ~.600 lift cam on these springs and after the first track appearance, I can say I'm not too happy w/them.

I missed 3-4, over rev'd slightly and both #1 and #2 exhaust valves met the pistons enough to bend them and leave a slight mark on both pistons.

918's are supposed to be good to .625 lift and 7500RPM... I don't think I went past 7500 @ all. My limiter is set @ 6800. Why would this have happened? I'd love to call Comp Cams and ask them... but havent had the chance to do so yet.

What other options do I have for springs without breaking the bank? I see Precision Racing spring kits @ TSP but I think they will require machining for the seats...

ugh. Thanks for any pointers folks.

 

I would not blame the springs, You missed the shift not them.
A stock ls1 will do the same thing and bend pushrods, I am sure you have good pushrods so other parts will be damaged instead .

I shift my car at 7300 some times and never see valve float. I use the new style 918's on both my cars.

 

Honestly I think your pointing the finger in the wrong direction. A valve spring isn't the root cause of bending a valve. You are running a cam with a decent amount of lift, did you check piston to valve clearance after the install? If you missed a gear and bent valves, I would measure your PTV clearance before spending any money on springs. You may want to fly cut, or change your cam timing.

When you look at at spring being good for up to a certain lift it is because of coil bind, not piston to valve clearance.

 

with a 600 lift cam i would run double springs to be safe. i consider beehives for tr224s and such with .564 lift. i have banged the limiter a bunch of times with my PAC 1218s on my tr224 and never one problem. i also have a 6400 rev-limiter.

 

I didn't blame the springs for missing the shift, but I am blaming them for not getting the valve shut before it hit the piston. This motor is not stock, nor are the pushrods (none of which bent either). I too am using newer style 918s, but after this I'm not sure they'll be staying on the heads for the next time out. The very first head shop I called to discuss my misfortunes said I was nuts for running these springs and told me to move to a double spring.

I did check the PTV clearances with putty when I put the heads on the short block. I had over .060" of clearance on the exhaust and even more on the intake. Where the valve contacted the piston was right inside the valve reliefs already cut into the pistons.

If coil bind is what decides how much lift a spring can handle, then these same specifications also have no implication as to how much valve float might occur based on valve train function around different cam specs, right?

I think this is what I need to look into. PAC 1218s. Got it, I'll research those.

Any other suggestions?

 

Sounds like your answer there. You should use the double springs instaed of the 918's for that lift anyway.

 

918s again, are rated @ .625" lift @ 7500 RPM. They let you keep the stock seats and therefore cost quite a bit less to get installed, saving you the machining costs of double springs with hardened seats and whatnot.

I went the cheap way out, I now I'm paying for that. I was really looking for what double springs are best to use.

 

I would always use the spring or a similar spring to the one recommended by the cam manufacturer.



.060 PTV clearance in not enough, The minimum I would recommend would be .090. The thing here is the faster you spin the engine, the more likely you are to have a variance here. This is why you bent the valve. There are two ways to fix this:

1. fly cut the pistons
2. adjust cam timing

A springs job is to apply pressure on the lifter to follow the cam, while at the same time closing the valve. They are not there to prevent PTV interference. When a manufacturer gives you those specs they do so as a max operating range. When you go beyond this range, springs are susceptible to coil bind and even worse breaking. Increased spring pressure could help, but would not be a fix for your PTV clearance.

 

Let me start by saying, I personally think you are absolutely at fault. This has nothing to do with the valve springs, period. You can break anything and everything with abuse... and you abused your setup. Consider it a lesson learned, blame no one but yourself....Grow up, being an adult means taking responsibility


.060" on the exhaust is your first clue, this is WAY too close. The exhaust valves are 1500 degrees and do not like to be touched at all. Intake valves can stand a tighter tolerance because they aren't so hot and they are pushing on a piston that is moving away from them, while the piston is charging at the exhaust valve.
This tells me you REALLY screwed the pooch, and reaffirms its was your fault. The piston and valve are closest at about .150" (ish) lift, not at full lift. So you were lofting the valve terribly. If you understand anything about valvetrain you'll know that EVERY system has its limits. Some systems are perfect at 7000 RPM and at 7002 RPM are completely unstable and tear EVERYTHING up in an instant! If you didnt, you do now I hate to see this happen, and Im just being honest with you.
Its coil bind and installed height that determine the physical limitations of the spring. Now there is "Distance to coil bind that is a measurement of how much travel is physically possible for the valve to float or loft after full lift.
Those wont save you from yourself either, nothing will except you. I suggest you take responsibility first thing, everyone wants to blame everything on companies and its just tiring to see people goof up so bad, and to try to come bash products, no matter what the product, on a public forum.

Most of the time people had no right installing or doing what they did, or in your case intentionally or unintentionally went way beyond the intended limits of the parts and broke something. THEN DONT WANT TO TAKE ANY RESPONCIBLITY!!!! Its like watching Judge Judy, no one gets it....

This thread should say "I over-revved my car tonight and blew it up " That's it, maybe a little about what happened and how bad it was for everyone to console you a little, but not to throw out excuses on why you don't feel responsible and the parts are to blame

 

like previously stated, for a 600 lift cam i would go with double springs. if you want to stay with a beehive then go with the PAC 1518 as they are rated to 650 lift.

 

.600" lift doesnt need a double spring neccessarily, blanket statements are never good. I run over .600" lift with beehives all the time, not ususally a problem, but I know if I hit instability to back off and save the engine.

And it also has nothing to do with the limitation of the springs ability to handle lift. They could have been PAC, PSI, Crane, Lunati, Comp, etc, etc, and been able to handle .800" lift and it wouldnt change a thing. Those are all good parts, its the obvious abuse the parts took that caused the issue.

 

^^^^WOW ^^^^

 

Ahhh its nothing, its not liek I dont like the guy, Especially with the way almost everyone is penny pinching these days, I dont wish this on anyone.

Just a little "Honest Time". I went a little harsh to try to grab his attention then open his mind to other possiblities besides throwing innocent things under the bus....

I even left out the part about the springs being rated to 7500RPM...

 

For double springs, I used some Crane double springs with my TREX (.608/.612 lift). They did not require any machining to the heads. Not sure on the Crane part number, but Thunder Racing's number is 40-144832-16. Not sure on price, I bought them as a package deal. Good luck!!

 

I have used 918's for over 12 hours of road race track time with my TSP 233/239 .600 cam, but I'm not winding it to 7500, I shift at 6500. I asked for extra valve clearance when I ordered the pistons. I have close to .120 clearance on the exhaust.
The piston chases the exhaust valve up the cylinder, weak spring or over rev, that's where it hits. Those 918 springs are perfect for what I am doing, IMO they are not strong enough to run 7500. No margin of safety if you over rev.

 

Just save yourself the headache and put a double spring on it - you don't want to see what a 918 does if it breaks...

921's (double) with 30k on the clock, excellent, no issues at all

 

Yep, sounds about right. If I dropped a valve, I'd have been out for another year.

I think I'm going to go with the Patriot 8501's.

 

Patriots won't save the motor in this situation either. You are better off with the lighter setup that a beehive provides. You may want to do a little more investigation before just slapping in the Patriots. Doesn't sound like PTV is enough as previously stated. Engine was already too close to the edge, any mis-shift and you will be screwed.

Rated spring lift capability doesn't mean anything.

 

Are you going to recheck your ptv and cam timing when you change your springs. Even if you put the motor together perfectly the cam could be ground a few degrees off which will screw up your ptv.

 

One more thought. Valvesprings need to be considered 2 ways.

1 will they tolerate the lift of the cam?

2 can they keep the valvetrain stable with the lobe profile you have selected
(just b/c they will handle the lift doesnt mean they wont look like a slinky at 7k with an lsk lobe)