I tried to do a search about Valve Spring pressure but I could not find any info. My questions is, how do you know when you have enough vs to much spring pressure without the side effects of your cam lobe been grinded away or your lifters been damaged by the spring pressure. Is there is a formula to determine what is the right valve spring pressure for a determine Cam? Thanks....

 

Good question. I wish I knew the answer. What you said though implies what I believe, that the best spring is one that 1) doesn't break and 2) is the lowest pressure able to avoid valve float and the other problems you mentioned and (3 has the lowest mass. I've chosen the Comp 918s to go with my Comp 222/224 cam. I hope they're the right choice; I'll find out pretty soon on the track.

 

Edwin,
The supplier of the cam will be able to tell you what the spring requirements are for any cam you buy from them. Most of us stick with the hydraulic lifters which with proper springs can handle around 7500 RPM at a maximum.

But there are limts to how much spring pressure these lifters can handle before they collapse. A professional race engine builder here in town told me that the LS1 and the LS6 can handle about 130 Lbs of seat pressure at a maxamum. After that he says the oiling system has a hard time getting them pumped up properly. I would suppose, and I am just making an educated guess here, that these limits tend to show themselves at lower RPM levels since the oil pressure is lower at low RPM.

I have a pair of 2001 LS6 heads with only 2000 miles on them. When I had them ported I had the guys at the shop put their spring pressure measuring tool on them. The seat pressure was only 80 Lbs.

By contrast my Comp cams 228 duration 588 lift 114 LSA cam called for the 918 springs. These have a seat pressure which is right where my race engine building advisor said the limits were, 130 Lbs.

I have an A4 and I have the rev limiter set at 7000. I shift at 6500. However if I leave it in first gear with my 3.73 gears in the rear I can be on the limiter before you can say "Oh My God!" for real.

 

I carefully tested all my Comp 918 springs @1.800 installed height(new), and 8 measured ~120#, 7 at ~125#, and one at ~130#. They do lose some pressure after a few heat cycles. I have a .560 lift cam and it rev's to 6500rpm without any problems........

Stan

 

Thanks for the comment, Stan. Did all your springs spec at 1.80 installed height without any shimming? Interesting variation in seat pressures but all within 8 percent. Were those pressures taken at install or after some miles? Lift on my cam is .566/.568 w/ moderate ramp so I think they should be fine. I'll check them next year after I've put on some track miles. Thanks again.

Cass

 

I checked pressures before I installed them with my bench mounted spring tester. During the install I height mic'd my valves using the new titanium retainers, and all were within 0.010" of each other (1.800 +- 0.005"), so I didn't require shims. Your cam setup should work well with the 918's. Some people suggest dual springs for safety, but I chose single springs based on my moderate lift and ramp rates. The Comp beehives are great for high RPM harmonic suppression too.

 

Thanks again, Stan. Sounds like you may have already seen this but I'll post it anyway just in case. Sounds like a solid design. Hope they work well in my car too.

http://www.krcperformance.net/newcontent/beehive.html

 

Thanks guys for your imput to this thread. I just wanted to know if there is some kind of formula to determine the pressure exerted on the valve train (i.e. lifters and came lobes) by a particular spring ... Manleys, Comp Cams etc... Does the pressure place in a valve spring before coil bind is achieve has something to do with that hypothetical damage??? And I mean the damage reciprocated to the valve train.

 

Wish I could help you with an actual formula but I doubt one exists. The best sources of info, I think, would be vendors like Comp who make the parts or tuners/engine builders who have enough knowledge and experience to provide good guidance on what works and what doesn't. There are plenty of sponsors here that could help you out. If you want to try another source, LS1tech.com's internal engine board has some serious engine fanatics who might be able to help you out. Good luck.

 

Thanks tcm c5...