Ok guys I got a question about valve springs and lift.

I have AFR heads with their #8017 springs which are LS1 style (not beehive) 1.29" diameter springs. rated at 1.800" installed height, 135lbs on the seat. 340 lbs open pressure at 1.23"

Coil bind is at 1.050" as advertised. Spring rate is 360lbs per inch.

AFR says max recommended Lift is .600". My question is why??

At 1.800 installed height, and 1.050" coil bind, thats .750" of lift. Now add in an extra .050" for clearance from coil bind, thats .700" lift. From everything i've seen, a springs max recommended lift is about .050" from coil bind at the installed height. These springs theoretically will handle .700 with plenty of clearance before it reaches coil bind. Hell, if you want .100 " of clearance from coil bind, thats .650" of lift.

Where do they get this .600"? is that for spring life?

Reason i ask, is my cam grinder is recommending near 155lbs on the seat, and shims of .060" to get that pressure at the 1.800" installed height. If they are only rated to .600 as AFR states, a .060 shim will kill my lift to .540"
I want atleast .570".
If I'm right by my specs, then with .650" of lift with .100" coil bind clearance, and then .060" of shims, i'll have .590" which is PERFECT

Any thoughts?

 

Its not just coil bind that limits max lift. More than likely the locks will hit the guide seal first. Also they are likely going to the side of production tolerance caution with the spec.

If someone is building up the heads, give him your cam spec and go from there.

 

Thats what i was figuring, so i will probly need a stiffer spring at the same installed height, or go with a taller spring/installed height that has the pressures i need, but then i may need taller valves which would suck.

I'll be building the heads up. I got them already assembled, but the cam i want to run will need a slightly more specific spring so i'll have to upgrade more than likely, else i'll have to cut down on the cam aggressiveness/lift which i dont want to do.

 

Shims wont affect the distance from lock to seal.

 

let me get this straight, i can shim it .060" and the spring still should handle .600" lift?

that does make sense lol, that decreases coil bind clearance but judgin by the specs, i have plenty of clearance anyway, i just dont have retainer/lock to guide clearance. I only have about .600 to work with when the spring can handle more, correct?

Thanks for your help!

 

Yes from what you posted the spring should be fine. In any case always check what you have, because you never know... best to be safe than sorry. Checking clearance is fairly easy to do. You can assemble it without the spring and measure between the locks and seal and see what you've got... and check them all while you're at it. Knowing the installed height would be nice too.
If at all possible I'd also check those springs and see if they really are what AFR says they are. A valve spring checking tool will tell you, if you have access to one.

 

i'll probly get one just to have or borrow someones. thats a good idea. i already measured the OD with a caliper and its 1.29 inches so thats a good sign.

thanks for the help... i'll pull a spring off and check the height with a micrometer