Valve Spring/Coil Bind/Set up

I was helping a friend yesterday that has been having some valve train issues. I am a little baffled to be honest.

He has .519 lobe cam 1.78 rocker which is .923 lift, he had run .018 valve lash so .905 lift. He was running a PAC 1361 spring installed at 2.105" That spring coil binds at 1.215" so that left .890" room for lift. I asked him how did you install it at 2.105" when you have .905 lift and only .890 till coil bind.

Long story short we put a dial indicator on the motor with actual spring pressure and came up with a max of .863" lift which is .027 from coil bind tighter than most want to see but my question is, you can see very clearly that the coils have contacted each other but how is that possible with .027 clearance?

I started thinking about it and maybe when the engine is hot the cylinder head grows but the intake valve does not making the .027 he thought he had even less.

I have always set my stuff up with cam lobe x rocker ratio minus lash. He said he used to do it the same way until he was told by manufactures to check with an indicator.

So how far from coil bind is too far and how tight is to tight and why? I have a hard time getting my head around how the coil hits with any amount of clearance I would have thought that the clearance will running is even larger than it is checking on a stand do to flex in the pushrod/harmonics etc.

Thanks,
Billy Thompson

 

springs

I posted a spring scenario last week and did a bunch of research on it.
To answer your question my data says .040 min to .060 coil bind clearance on a high rpm hemi. Apparently, at high rpm the valve will "loft" a little and eat up the room while at the same time flex will eat up some lift. Probably going to vary with every combo.

I measured my lift at the valve with correct springs and set my clearance as close as possible without exceeding 530lbs seat. It came out to .060-.080. I made 3 passes and saw zero improvement in spring happiness. 3 intakes lost almost 50 lbs. This was shifting at 9000 rpm.

We're testing/racing next week and I will probably shim some springs all the way down to the minimum to see what happens. Pac assured me that when the spring is happy the losses will reduce...I don't buy it...I have substantially reduced the coil bind clearance and it hasn't done anything positive except squeeze out more runs before they hit the trash can.

I will most likely switch to PSI springs next year.

 

Pac has been having major issues on spring diameter lately. To the fact that most pro stock cars have left them. You need a Rimac to test. I've seen same set differ .050 in bind. Not a good product at all right now

 

Funny you talk about them varying because this particular car was beating random intakes when all shimmer the same.

Kind of prove that they didn't all have same distance to coil bind.

We are putting a PSI on now installed at 2.165, then coil bind at 1.180 so that gives us about .075 to coil bind going off of cam card and factoring lash. They went in about 540lbs at 2.165" we are hoping this combo can turn 10k plus with a 124g intake valve.

 

I've heard guys say that you should never trust the spec, always put the springs in a vice and measure coil bind on each one. I'm not sure I trust my vice that much.

 

Promod83. Your friend is doing something off. Not sure how he got his numbers but this is what I would be doing. Gross lift (I always include lash as many times you take that up in loft) +.060-.100 CB clearance + true coil bind. To find true bind you only need to check the outer spring. This is the spring 99% of the time will CB first. Lets say his springs CB at 1.210". We take that 1.210" + .923" + 0.060"=2.193" installed height. I am sure your friend is killing his springs extremely fast due to taking them into bind. He may even be having issues with breaking rockers and burning up pushrods.

Jay70Cuda,

Not sure where you are getting your information from but that is not true.......

I am not here to start anything but rather help out and answer any questions you may have.

 

Almost every 410 sprint car engine my guy has built ran Pac . They have started turning out springs so fast the quality has gone down. That was the first discovery then Pac introduced the tvs springs and they cost way more. Aka they check every wire all the way thru now. I have facts to back all this either way. I've never ran into a problem with the 1360 spring. 1355 yup. Not very consistent at all. Several sets. Different CB rates and install psi varys off there numbers as much as 35-40 lbs. I've don't run spring that close to CB due to if you damage one at the track and you happen to get a hold of one of those fat springs. Well..... Your tossing them at 40 runs anyways. Leave yourself wiggle room. Never once dropped a valve of tore up valve train parts once I did this. Jmo