stock valve springs

pfordamx · 11-25-2011, 05:43 PM

Ok I was just wondering if some of you guys could clear this up for me. After reading this forum for some time I've noticed a lot of people talking about running some pretty high valve spring pressures in stock. Which to me doesn't make since a motor that your only allowed .500 or less valve lift I figured the object would be to run the lightest spring you could with out valve float or coil bind, because it has to take more power to compress a stronger spring, the only thing I could think of is the rpm your turning must mandate the higher pressure spring so you don't float valves

Jeff Lee · 11-25-2011, 07:38 PM

Very radical cam lobes, often described as "square lobe" which will bounce the lifter like it is on a trampoline. That and high RPM.

pfordamx · 11-25-2011, 09:28 PM

ok i've always heard of square lobed cams, and associated it with lots of duration and very agressive ramps almost like running a solid roller with flat tappets. but i didn't realize they were aggressive enough to require that much spring or that they would actually bounce the lifter like that, probably under estimating how much cam is in most stock class motors.

Jeff Lee · 11-25-2011, 11:50 PM

You might have a .280" lift measured at the cam lobe with a 1.5 rocker ratio for .42" lift measured at the rocker arm.
It may be packing' the same duration numbers as a .450" lobe lift / 1.5 RR roller cam that measures .675" at the rocker.
That's .170" difference in lobe lift. Picture that in your mind.
And it really is fun on test-n-tune night beating the back-halved, roller camed, dominator equipped big engine with a Stock Eliminator car!

11-25-2011, 05:43 PM	#1
pfordamx Member Join Date: Sep 2011 Location: Oklahoma City, OK Posts: 214 Likes: 3 Liked 7 Times in 5 Posts	stock valve springs Ok I was just wondering if some of you guys could clear this up for me. After reading this forum for some time I've noticed a lot of people talking about running some pretty high valve spring pressures in stock. Which to me doesn't make since a motor that your only allowed .500 or less valve lift I figured the object would be to run the lightest spring you could with out valve float or coil bind, because it has to take more power to compress a stronger spring, the only thing I could think of is the rpm your turning must mandate the higher pressure spring so you don't float valves

11-25-2011, 07:38 PM	#2
Jeff Lee VIP Member Join Date: Jul 2007 Location: Anthem, Arizona Posts: 2,766 Likes: 0 Liked 3 Times in 3 Posts	Re: stock valve springs Very radical cam lobes, often described as "square lobe" which will bounce the lifter like it is on a trampoline. That and high RPM. __________________ Jeff Lee 7494 D/S '70 AMX

11-25-2011, 09:28 PM	#3
pfordamx Member Join Date: Sep 2011 Location: Oklahoma City, OK Posts: 214 Likes: 3 Liked 7 Times in 5 Posts	Re: stock valve springs ok i've always heard of square lobed cams, and associated it with lots of duration and very agressive ramps almost like running a solid roller with flat tappets. but i didn't realize they were aggressive enough to require that much spring or that they would actually bounce the lifter like that, probably under estimating how much cam is in most stock class motors.

11-25-2011, 11:50 PM	#4
Jeff Lee VIP Member Join Date: Jul 2007 Location: Anthem, Arizona Posts: 2,766 Likes: 0 Liked 3 Times in 3 Posts	Re: stock valve springs You might have a .280" lift measured at the cam lobe with a 1.5 rocker ratio for .42" lift measured at the rocker arm. It may be packing' the same duration numbers as a .450" lobe lift / 1.5 RR roller cam that measures .675" at the rocker. That's .170" difference in lobe lift. Picture that in your mind. And it really is fun on test-n-tune night beating the back-halved, roller camed, dominator equipped big engine with a Stock Eliminator car! __________________ Jeff Lee 7494 D/S '70 AMX