[Bersaglieri]

Did a cam swap on a LT1 350, cam is a hydraulic roller 218/228 .541/.541 112LSA GM Hotcam. Installed height is ~1.750" on the Isky 235D valve springs [130 seat/320 open]. Comp Stainless 1.65 rockers, .080 wall 1 piece pushrods, LS7 lifters, all brand new.

I gave the motor a few casual revs with the covers off and noticed a few valve springs/retainers spin. Takes a 7-8 hard revs to get them to make 180* of rotation. It's only happening on 3-4 cylinders, while the rest do not move that I could see.

I'm hearing/reading two different things. One that it's valve float and must be stopped. Two that valve springs can and will rotate like that and as long as it isn't excessive that it's not a problem. I guess my question would be 'what is considered excessive?'.

I'm not sure what to think. The springs are rated to .550 lift with could bind a 1.150. I tested a few of them and they are testing at what Isky rates them at, so they should be able to control the valve train right?

In my search for an answer I found a few videos like this from PAC.

http://www.youtube.com/watch?v=019Jyn9oB5k&feature=related

Thoughts?

-Dustin-

 

[84ta406]

Thats not a lot of clearance between max lift and what the springs are rated for, are they binding at all?

 

[Bersaglieri]

I don't believe so, although I'm hoping to go through and measure the installed height of every spring today. The ones I measured during install ran 1.750ish. They coil bind a 1.150, that's .600 lift to bind, ~.059 clearance. Isky recommends .050 clearance.

Are the Hotcam lobes [272/281 @ .006 lift] with 1.65's just too much for these springs? I'm planning on calling Isky on Monday to see what they say.

-Dustin-

 

[SStrokerAce]

I'm going to take a shot at this Dustin because I know you ;-) The spinning you see is due to the coil wound in the spring. A spring is basically a torsion bar wound up to save space, and the coil will dispurse some of the potential energy into thrust to spin the spring. Some springs never spin since there is enough friction by the valve in the guide, valve to seat, spring to locator, locator to guide/head preventing it. In the end it's the reason that when you lap a set of valves the lap line is basically polished off when you run the heads.

Valve float adds more of a wobble to it, or a BAD surge in the coils.

It's natural that some setups do this, I wouldn't worry about it.

Bret

 

[Turbobuick6]

Exactly what Bret said.

Now if your breaking tip and the ends are bluing you have a problem. Usually you don't see this on a street car though.

 

[Bersaglieri]

Thanks Bret and turbobuick6, I was starting to worry when no one responded.

I'll start beating on this bitch, monitor the valvetrain, and advise if anything abnormal happens.

-Dustin-