How many miles are Comp 921's good for?
 

I have probably 20K on my H/C setup and going to go get it retuned in the very near future, but was curious how many miles 921 springs are good for? I have AFR205's and a 224/228 114 with .581/.581 lift which isn't taxing on the springs I know, but should I change them out when I get it tuned?

Thanks.

you can just pull one off and check it, the only way you will really know

Personally I would swap them, valve springs fall into the ounce of prevention category.

very true vettenuts, as its just a function of how many revolutions the springs go through that will determine how long before they fail. The amount of lift on the cam doesnt have as much bearing on the spring life as how harsh the ramp rates on the cam are.

Anyways sorry that wasnt to answere you were looking for. I would say either check them, or just get new ones.

OK, so when I check them what do I look for? Not sure how to tell if they are fatigued...

I pull all of my springs and check each winter. Buy pulling one, the question is which one to pull?

I like the 918s and now the 921s very much. light wt and Not too strong.

my only driving is on a road course with constant 3000 to redline 6700.for 20 to 45 min at a time, 3 to 4 times a day, two days every month.

My cam is a 224/224 581/581 112 on a LS6 with polished LS6 heads. and I do use sodium filled valves.

Too much spring effects valve seat pressure and release.

just find a machine shop that has a spring tester. Basicly just a way to comperss the spring to a determined hight and see the force in pounds it produces.

Just look up the specs for the springs, i'm pretty sure its 135 lb. @ 1.770 and 400 lbs. @ 1.220. I would double check though this is just off the top of my head if i remember right. So you just compress the spring to those hights and measure the lbs of force its makeing. that will tell you the condition the spring is in.

Each cylinder will have different dynamics, so you really should pull them all.