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Old 12-31-2010, 08:36 AM
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Valve springs, heights and rates. ??

Ok so I bought a 60102 voodoo to replace my trick flow track max cam. Lunati recommends the cam be installed with springs that are 100 lbs at 1.75 in installed height. My trick flow heads have springs that are 120 lbs at 1.78 in installed, but the trick flow springs have a spring rate of 360 lbs per inch whereas the lunati springs have a rate of 462 lbs per inch. I know that not using the recommended voids warrenty but that's the least of my worries being that this is the third cam I've had in this engine since I built it two years ago. Realistically, what would happen if I use the cam with my existing springs? What if I just preload the lifters just a little bit less, like 1/4 turn instead of 1/2 turn? Thanks for all the help.

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Old 12-31-2010, 08:44 AM
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if you leave them loose it wont be opening the valves all the way.
and that wont change the fact that the spring pressure most be overcome to open the valve.
that i do know.
if your current springs will work? i do not know
but there are people here that do..
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Old 01-01-2011, 10:59 AM
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Well, where are they? I went ahead and installed the cam, adjusted the rockers 1/2 turn past zero lash. I'll be alright.
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Old 01-01-2011, 02:25 PM
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Quote:
Originally Posted by RotorHead
Ok so I bought a 60102 voodoo to replace my trick flow track max cam. Lunati recommends the cam be installed with springs that are 100 lbs at 1.75 in installed height. My trick flow heads have springs that are 120 lbs at 1.78 in installed, but the trick flow springs have a spring rate of 360 lbs per inch whereas the lunati springs have a rate of 462 lbs per inch. I know that not using the recommended voids warrenty but that's the least of my worries being that this is the third cam I've had in this engine since I built it two years ago. Realistically, what would happen if I use the cam with my existing springs? What if I just preload the lifters just a little bit less, like 1/4 turn instead of 1/2 turn? Thanks for all the help.
The amount of preload on a hydraulic lifter will not reduce the spring pressure.
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Old 01-01-2011, 02:35 PM
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Quote:
Originally Posted by RotorHead
Well, where are they? I went ahead and installed the cam, adjusted the rockers 1/2 turn past zero lash. I'll be alright.
Attaboy, buck up against the system. You sound just like me when I was younger. Knew all the answers. My way was the only way. Nobody else knew anything. Took a lot of years and a lot of tears to finally realize that things are done a certain way for a reason. You're making a hard row to hoe for yourself young man.

Now, I suppose you will break in the cam with those springs in place? Yeah, pretty stupid to change down to light springs just to break in the cam, huh? Well, good luck!

http://www.crankshaftcoalition.com/w...ips_and_tricks
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Old 01-01-2011, 02:49 PM
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Going on your third cam? What happened to #1 and #2?

Closed and open pressure, spring rate and installed height are all taken into consideration when choosing a spring for a given cam's lobe profile, lifter being used, RPM range, etc. You really should use the companies recommended spring installed at the recommended height.

If cam #1 & #2 lost lobes, you have to take the engine apart and clean it out or cam #3 will probably fail also. Not to mention following proper break in procedures.

Good luck!
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Old 01-03-2011, 11:12 AM
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cam 1 was a summit 1102, after that I bought a trick flow top end kit and the cam that was supposed to come with it was back ordered so I went to the next one up and it was way too much, rpm range was 3500-6500, ridiculous duration. I didn't have the rest of the car set up for it, so I got the voodoo 60102 so I can drive the thing on the street.

I know how to change the pressure with shims but how do you change the installed height? or is the installed height just a reference point for your pressure, like compress the spring to X height and read pressure and shim as necessary?

Last edited by RotorHead; 01-03-2011 at 11:20 AM.
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Old 01-03-2011, 02:43 PM
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Quote:
Originally Posted by RotorHead
cam 1 was a summit 1102, after that I bought a trick flow top end kit and the cam that was supposed to come with it was back ordered so I went to the next one up and it was way too much, rpm range was 3500-6500, ridiculous duration. I didn't have the rest of the car set up for it, so I got the voodoo 60102 so I can drive the thing on the street.

I know how to change the pressure with shims but how do you change the installed height? or is the installed height just a reference point for your pressure, like compress the spring to X height and read pressure and shim as necessary?
You get the installed height by shimming or cutting the spring seat deeper. If the pressure isn't correct at installed height, then the springs are worn out or you got the wrong springs or wrong height.

Last edited by Overdriv; 01-03-2011 at 02:48 PM.
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Old 01-03-2011, 03:38 PM
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I guess what I'm asking is, from the seat to the retainer is a certain height and you can't change the length of the valve, so what if the dimension from the seat to the retainer is a different height than the reccomended installed height? Or, is the installed height the distance you compress the spring and find your pressure? I don't know if I'm asking the question right but, the recommended height for my cam is 1.75 @100 and the springs on my heads are at 1.78@120. But even if I buy the springs from lunati I don't have the scale or any of the equipment to find the pressure or anything.
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Old 01-03-2011, 03:50 PM
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Quote:
Originally Posted by techinspector1
Attaboy, buck up against the system. You sound just like me when I was younger. Knew all the answers. My way was the only way. Nobody else knew anything. Took a lot of years and a lot of tears to finally realize that things are done a certain way for a reason. You're making a hard row to hoe for yourself young man.

Now, I suppose you will break in the cam with those springs in place? Yeah, pretty stupid to change down to light springs just to break in the cam, huh? Well, good luck!

http://www.crankshaftcoalition.com/w...ips_and_tricks
The only springs I have are the ones that came with the heads, what am I to do, go buy a set of soft springs just for break in? Look man, I don't doubt your wisdom one bit. If i thought I knew everything, do you think I'd be here seeking your advice? The springs are set up for a cam that has .480/.494 lift at the valve, and the cam I have now is .468/.489. The duration of that cam is .226/.224 and mine is .219/.227. Is .012 on intake and .005 on exhaust enough lift to make a huge difference is required springs?

Also, my existing spring have a rate of 360 lbs per inch and the lunati recommended springs have a rate of 462 lbs per inch.

Last edited by RotorHead; 01-03-2011 at 04:02 PM.
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Old 01-03-2011, 06:53 PM
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If you measure the installed height and find it to be too large, shims will bring it into spec.

If it's too small, you can use different locks and/or retainers to gain some installed height. There's a limit to how much you can add this way, however. Combining the two you might get up to +0.150"- but I've never looked for "plus length" retainers in 1.250" diameter.

To measure the installed height easily, use a snap gauge or inside caliper and measure that w/a vernier or dial caliper. If you're careful, you really only need a caliper w/the capability to do a "depth" measurement. This is where you use the rod that extends out of the bottom of the tool. Even a machinist steel rule will suffice.

More on valve spring tech HERE.

Don't worry about measuring the actual spring pressure. Instead of that, you are setting the closed and open pressures by setting the correct installed height.
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Old 01-03-2011, 07:40 PM
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I like the link, it's very enlightening. But I still have a dilemma, the springs that I have installed are installed at 1.780 but the recommended height is 1.75. Sounds easy enough to throw in .030 worth of shim but at 1.78 my spring pressure is 120 but I'm supposed to have 100. If I shim my springs .030" my closed pressure is going to be a lot higher than it is already, but it's already 20 lbs over the recommended pressure.
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Old 01-03-2011, 07:50 PM
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The springs you have now are quite a bit different than what you need. You really should get the correct spring and install it at the correct height.
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Old 01-03-2011, 08:08 PM
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ok, if that's what I need to do.
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Old 01-03-2011, 10:08 PM
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I think you will be fine with what you have, the springs you are using will have less open force than the Lunati does(about 30 lbs), which will help the lobe survive, and has more seat force(20 lbs), which you do need to prevent seat bounce/lifter pump up(often mistakenly referred to as valve float with hydraulics).

I wouldn't change a thing from what you have, your spring specs match what I'd want on there, I don't like the low 100 lb seat force figure Lunati gives, it is just too light. There have been complaints around the web of guys finding valvetrain/seat bounce problems with the light Lunati spring. Come to find out Lunati also lists a different spring for this same cam if you dig through the site and catalog - a higher seat pressure lower spring rate spring, and it is a near perfect match for what you already have.

I'd break the cam in with a light pressure stock set if you have them(would even be worth buying to use for break-in, cheap $30 springs from some place like www.competitionproducts.com), and use a good high ZDDP content oil and/or add a break-in concentrate with lots of ZDDP.
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