Valve spring calculations

[trotterlg]

I have a new set of LS6 valve springs for the 3.1 high compression build. They are rated at 90 pound seat pressure at 1.8 installed height, if I install them at 1.7 inches the seat pressure will be about 123 pounds. I put one in a vice and turned it down to coil bind, measured 1.177 inches. Added .025 inches and came up with a minimum open measurement of about 1.202 inches. This gives about .500 valve lift ability which seems more than necessary for a 3.1 performance cam. Anyone see any flaw in my coil bind/usable lift calculations? Open pressure would be about 285 lbs. The top stock 3.1 spring retainer fits perfectly and using a tophat type seat/seal from a SBC will work for the spring seat/locator. If I had deep pockets I would just buy new comp cam stuff. P.S. I still need a solid core hot roller cam. Larry

[geoffinbc]

Yea that sounds right but a healthy roller cam is capable of more than .5 lift. So you just have to keep that in mind.

[AaronGTR]

Yep, I'm going through all this right now. I was using a cam with a little over .51" intake .52" exhaust lift with LS6 springs, and that was a little too much. Top two coils were touching, and I worn out a lifter and the end of a custom pushrod. (check out my head gasket thread for pics)

0.50" is as high as I would go without either using the comp springs or machining the spring pockets in the head so you can install them at 1.8". I'm doing that myself because I don't want to buy new springs and I'd like a little less spring pressure since I'm going to a less aggressive cam. The solid core billet steel cam I had also F'd up my cam bearings and my oil pump drive. If you use the solid core OEM style cam for a regrind then you should be ok, but it wouldn't hurt to make sure your cam bearings are good first and that the cam bore is straight. I may be getting mine align honed and over size bearings installed.

[trotterlg]

Glad my calculations look reasonable, I may go with a little less than .500 lift and add a little duration, this will be a fast turner in a light car so a little low end loss would be ok. If your old cam could be salvaged and it is a solid core, I have a local cam grinder who could probably fix it up for me to run in my engine. Let me know how bad it looks and if you would like to part with it. I think your cam bearings look like mine, and my engine was fine inside, think that is some strange finish they put on them to let the cam run in. Larry

[AaronGTR]

The cam looks like it has no damage at all. I've already had one person offer to buy it off me, but no price given yet. I can give you specs if you want them.

[trotterlg]

I'd probably get it ground some because I need the exaust valve open less then .200 at TDC because of my iron head pistons, but I am interested, am a little concerned about it eating your oil pump drive gear. Were you running 1.6 lifters with it? Larry

[AaronGTR]

Stock roller lifters, custom pushrods, modified SBC roller rockers.

[trotterlg]

I think I will go with stock pushrods and adjustable roller rockers. Let me know what you would want for the camshaft. Larry