How much valve spring is to much for a cam.
How much valve spring is to much for a cam. I have always been curious what would be to much spring for a cam.I have a 585 lift cam in my car know not sure what springs is on it bought the car used like this.What would be a good lift spring to go with on a 585 lift cam?What would happen if you put to much spring on it like a 700 lift spring?Basically trying to figure out how much is to much?Would rule of thumb be 100 over the lift of cam?
the trick to this is getting the right spring pressure in the range your cam lives at. You dont want to put a spring in thats going to be 160lbs seat pressure and 400 lbs at your .700 lift (this is totally hypethetical). Basically youd only have about 275 to 300 lbs at open and thats not enough. A good .600 lift spring would be ideal for your case. comp 918, pac1218, or even a pac 1518 shimmed to the right height if you want the nitrided spring. Main thing is to get your spring shimmed to where it is near its advertised lift when the cam is fully open so that you have enough pressure in order to control the valve.
a lot of dual spring kits are .650 rated. Me personally I have the lunati gold duals and ran into valve float issues with the heavier retainers at 6800 rpm. I needed to shim them a tad since my cam is only a .610 lift.
well youll need to determine your lift, and the type of lobe you have on the cam. If its super aggressive youll need stronger springs. Your typical open psi on a street LS1 is 400lb open. Stock rockers don't like much more.
Too many people over-spring their motors. Unneeded spring pressure just eats up hp and is also hard on the rest of the valvetrain. You only need a good beehive spring with that cam.
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When chosing valve springs you need to look at the information given for the valve springs and compare it to your cam. For example, I am going to use PAC 1218's with a Comp Cam 220/218 .581"/.562" 111 LSA.
1.800"(recommended valve intsalled height)-1.140"(coil bind spring height)=.660" (spring opperating range)
.660"(opperating range)-.581"(max cam lift)=.079"(distance left before coil bind)
.079"(distance left before coil bind)-.050"(recommended tolerance before coil bind)=.029"
So if my math is right these springs will safely handle this cam with .029" of tolerance.
1.800"(recommended valve intsalled height)-1.140"(coil bind spring height)=.660" (spring opperating range)
.660"(opperating range)-.581"(max cam lift)=.079"(distance left before coil bind)
.079"(distance left before coil bind)-.050"(recommended tolerance before coil bind)=.029"
So if my math is right these springs will safely handle this cam with .029" of tolerance.
I would throw a .025 shim under the locator though and take the spring to its open pressure point specified my the manufacturer. I have .030" of my springs that I didnt shim for and ended up with some high rpm valve float
My thoughts too. If you subtract .029 from 1.800 you get 1.771". I would want the installed valve spring height to be somewhere between these 2 numbers. If I were above 1.800" then I wouldn't have the advertised 130lb seat pressure when the valves are closed, and would lead to valve float as you said. If I were under the 1.771" I could get coil bind. I think after I rebuild my heads I am going to shoot for 1.775-1.785" installed spring height. This will give me more closing force and keep me safe on coil bind.
