Not buying it. I would not even bother to check it. The only thing to check is the load, open and closed. If the spring weakens you will see it on the open and closed loads.
Stock 340 springs vs comp 901-16
- Thread starter 4spdragtop
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Not buying it. I would not even bother to check it. The only thing to check is the load, open and closed. If the spring weakens you will see it on the open and closed loads.
4spdragtop
Well-Known Member
So coil bind... Take installed height(say 1.65") SUBTRACT the MAX valve lift(0.468"). Leaves me 1.182" Correct? Coil bind is at 1.100" so we are safe there?
Thanks all!
Thanks all!
nm9stheham
Well-Known Member
Yes you are; I think you are getting this stuff down!
nm9stheham
Well-Known Member
Yes it will. But if you do not have a spring tester, then free length is all you have to check for spring weakening. Hey, I ain't gonna force you to believe anything.... but it is a parameter that has its uses.
The spring ends distort take up some extra compression distance when you first start to compress the spring; that makes the spring rate deviate from linear when you get close to free length. So taking the spring rate and the difference between free length and installed height won't compute out like when the spring is working in its linear range.
4spdragtop
Well-Known Member
I was going to spring test them but I didn't want to bug the machinist. I looked at cheap spring checkers and they ain't cheap.
So I wasn' going to buy one. A free or installed height out of spec would be a test I could do myself and be an indicator.
When I ask questions I also want to know how we arrived at that answer. I may ask lots and they seem to domino lol. But I' weird in that I like math and a lot of these questions/answers boil down to math.
I do appreciate the help, I realize how much work is involved in getting the answers.
Thanks all!
So I wasn' going to buy one. A free or installed height out of spec would be a test I could do myself and be an indicator.
When I ask questions I also want to know how we arrived at that answer. I may ask lots and they seem to domino lol. But I' weird in that I like math and a lot of these questions/answers boil down to math.
I do appreciate the help, I realize how much work is involved in getting the answers.
Thanks all!
4spdragtop
Well-Known Member
Installed height with 747 retainers and no shims or springs.
#4 EX 1.6875" shim 0.0590"
#4 INT 1.6955" shim 0.0585"
#4 EX 1.6875" shim 0.0590"
#4 INT 1.6955" shim 0.0585"
I have a spring tester. When I didn’t, my machine shop or Jim at Racer Brown would let me check them on theirs. You better be in the spring’s linear rate between closed and open, or you are using the wrong spring. You better be in the ball park with recommended springs if your cam manufacturer does not give you the specs. There is no reason to check free length. Closed spring height should not be close to free length. High Performance valve springs are ground flat on the ends and are made of very high strength alloy steel. If you are building a High Performance engine, you better be checking everything, or trust someone is doing it for you. A lot of us can tell all kinds of horror stories of things we have found.
nm9stheham
Well-Known Member
If you have the tools, by all means use them. If not, then you have to make do.
BTW, as for being in the linear range, for sure that is the case with straight coils. It changes with beehives, as those are progressive rate springs. So you are not in in a linear spring range with those; part of the point of them is to have the natural frequency of the spring/mass changing, to help avoid resonances.
BTW, as for being in the linear range, for sure that is the case with straight coils. It changes with beehives, as those are progressive rate springs. So you are not in in a linear spring range with those; part of the point of them is to have the natural frequency of the spring/mass changing, to help avoid resonances.
You are spot on about the math; it's a very good tool for some of these issues. It's heartening to see someone 'getting it'!
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