VALVE SPRING COIL BIND QUESTION

I understand the theory behind setting up valve springs close to coil bind eg 0.050-0.060. However, is it that critical in a street strip engine that isn’t seeing constant high RPM. I have found a float issue in my new bullet at approximately 7000rpm. Problem is, I only have 0.640 lift (nett with deflection measured at the retainer), and any solid roller spring worth their salt sets up anywhere from 0.160 to 0.200 from coil bind. And no I can’t shim my current springs any more. It isn’t a pressure issue, more like a frequency problem.
Some say don’t worry and others say it’s super critical. Thoughts please?
Thanks in advance.....

Valve float causes all kinds of havoc in the valve train, it ain't a ship, don't float them
As far as distance to coil bind that is done, to my understanding from several different cam techs, is to prevent harmonics from the coils in the springs at the upper RPM.
On your deal, problem, you didn't say if it is a flat tappet or roller cam and or what seat and open pressures your dealing with so if it is floating them at 6400 not do to hydraulic lifters pumping up the you have two choices, change the springs to another type and or shift it before 6200 RPM
BTW I set all my motors up with more seat pressures than most cam company recommend and shoot for within 10 lbs. at the open height to start with based on lower seat pressures allow the lifters to float at max lift more than when you have more seat pressures on flat tappet type lifters, solid or hydraulics 140 to 175 on the seats and up to 375 lbs. at max lift and try to get from .050 to .100 from coil bind. Which is not always do able with the valve springs available today.
I'm bless to have a large supply of new and old valve springs, a very good valve spring tester and a lot of valve spring shims to shoot for perfect on all 16 springs
Please let us know what you do and the results That will help others on here as well

How do you know it’s a float issue ?

What are the symptoms?

Solid roller.

We could hear it on the dyno and when I removed the rockers and there was a text book pattern on the valve tips.

It could be as simple as a similar spring with a different spring rate is needed. As you mentioned, the spring you're using is hitting a frequency that is causing it to go in to surge, it's likely a similar spring of a different rate won't do this.

Tom Vigue has done some testing on his spintron where he mentioned running the spring around 0.200" from bind without any issues.

Found some cool iskys but .160 from coil bind.

You said you "only have .640" lift". Lift isn't the primary factor in valve float. Lobe shape is! Cams with .400" - .500" lift can float early if not properly set up. (i.e.: NHRA Stock Eliminator cams often referred to as having "square" lobes".)

If you can't "shim" your springs more, can you get more pressure (open as well as seat) from the other end using -.050" locks and/or retainers?

I'm no cam expert, but I had valve train issues and caught retainer damage before it let go all the way. Going from 160/360 to around 200/400 made a difference and even helped maintain more consistent valve adjustments between checks.

What is stopping you from adding more shim? I recently shimmed mine to .050-.060 and had to add a good amount of shims, but comp said as long as I could get the valve seal on not to worry about the shim stack. I haven't run it yet to see if there is a performance difference, i wasn't having a problem before but did this off of comps recommendation.

What spring?
what installed height?

Closed & open pressures w/ current spring?
How close to coil bind w/ current installed height?
What type (diameter & wall thickness) & length are the pushrods?
How much deflection between measuring lift w/ soft spring and measuring with actual spring?
What type of rocker arms & what ratio?
What type of cam lobe ("Drag", "Endurance", ?)?
What's the hot lash setting?

Also, what could you "hear" on the dyno? And what did the dyno data indicate (e.g., valvetrain "crash", or no incremental gains or even losses of measured air flow at RPM intervals, or screwy AFR readings, or...)?

Spintron has rudely schooled me on coil bind. Back in the day, everyone assumed that (with symmetrical springs) each coil will collapse separately and simultaneously, and the inter-coil distance will shrink but remain equal to full lift.
This never happens. The top coils smack each other long before full lift, and this collision is added & subtracted to the position and stored energy of every coil.
A spring at full chat looks like a slinky.

But did you see anything that shows the benefit of setting up the spring to lift closer to coil bind to help reduce the harmonics or spring surge? Or is it a tradeoff where it can help tame the surge, but at the price of weakening the spring prematurely?

"Full chat" - You're originally from the UK, right? Never heard that expression used elsewhere...

All of the reccos I've seen are just trying to avoid coil bind while using the shortest spring. Other benefits? IDK.

PAC 1343. Installed at 1.870.

255@1.870
610@1.230
7/16 full taper with 0.165 wall
Deflection is approximately 0.020 with spring
T&D rockers 1.6 ratio
Crane 0.427 SR lobe with 1.050 base circle
0.020-0.022 hot
You could hear a flutter at 7000. The dyno reflected this with a squiggly line then suddenly drops off. Also tips of valves have a snow angel pattern.

set up looks ok. What is the condition of the valve job/ guide?

Not that I'm an expert on this stuff, but nothing appears "wrong" from the parts description above.

What type of cylinder heads, valves (material, length & size) and spring retainers (material)? Trying to get a sense for how heavy the valvetrain components are...

An "out of the blue" question: How old is that Crane lobe design? There have been lots of advancements in lobes over the years w/ the advent of Spintrons, etc., and some newer designs are promoted as having better high RPM dynamics than comparable older lobes.

Does that cam have the early Hi Low No Pop lobes on it? They had inverted flanks, those lobes would start to open the valves and then let them close a little and then go to max lift
they didn't make them very long either
Cam lobe designs have changed a bunch in the last 30 yrs, especially drag race lobes
Good luck on finding and fixing this problem

I haven’t removed the heads. Was hoping to just swap out the spring.

W5 heads
Ferrea 5.165 6000 series 11/32 Stem 2.08 and 1.60
Comp tool steel retainers with X2 -0.100 moly locks
Allegedly the lobe is a modern design and is improvement on the old 420 lobe
There are a lot of engines over here using that lobe and some spinning them to 8000 with no float issues. Mopar, Chev, Ford and GM Holden engines.
Got me stumped!

I have been told the 427SR lobe family is a modern lobe design. A so called improvement on the old 420 lobe family.

Was assembled with new exhaust seats, fresh 3 angle job and new guides. All was mint when checked and installed.

Not sure that I was looking in the latest Crane lobe catalog, but there wasn't a 427 series. There is a 428 series, which is described only as an aggressive oval track design.

Maybe you need to look into whether a different spring might be required to keep things under control. Not sure what else to suggest at this time.

What is stopping you from adding more shim?

He's already close to the minimum installed height for the combination described: 1.870 with .640 net lift means he's down to .080 before coil bind, per the 1.150 spec for that spring.

Sounds like a spring change is the next best step. I'm pretty sure a comp 944 would fit right in there and put you around 270 closed .

Possible rocker arm geometry problem, call Mike at B3 racing.

He was the reason I went T&D in the first place.

I’ll have look!

Crane told me it was a SR lobe with 0.427 lobe lift.
Wondering if the reduce base circle of 1.050” and relatively short duration 304(266@50) and 308(270@50) with only 0.427 lobe lift makes for an inherent aggressive lobe design.
Just try to cover all bases.

Does it transition from "OK" to "Chaos" over only a few hundred RPM, or can you see things in the data getting progressively worse over maybe the last 800-1000 RPM until it comes unglued?

I still think you need to explore other spring options.

From where I sit........ which is from a position of having not tested any of your stuff...... it certainly appears as though that spring, in that application, with that cam/RR ratio........ isn’t a match made in heaven.

I doubt fiddling with the installed height is going to fix it(but never say never).

I’ve tested many SBC’s with similar lift cams, using stud mounted rockers in Dirt modifieds that would go to 8K with less spring than you have........ and many of them used fairly aggressive cams.

With what you’ve got into springs/retainers/locks, etc....... it might be less $$$ to use a different cam profile and keep the springs.

If I were to look at different springs, I’d be tempted to try something with a damper..... or perhaps if you have enough available installed height, something like the new conical springs.

The only “SR” lobes I see in the lobe master catalog are designated “street roller” profiles(nothing with that lift though).
Perhaps the high rpm stability wasn’t a primary design parameter for that series of lobes....... and they just aren’t all that happy at high rpm.



Do you know the checking height for the 304/308?
If it’s .020”......... that’s not an aggressive lobe at all...... at least the intensity near the seat doesn’t look to be.

Even an old Comp hi-tech.420 would be 302/306 @.020 for 266/270@.050........ and those lobes are pretty smooth.

Do you know, or did you check the duration @.200?

Yep, chaos in a few hundred RPM.

Yes, the checking point is at .020. And stupid me didn't check the numbers at 200.......

That info should be in Crane's lobe master catalogue??

Apparently not.

Was the cam a custom-ordered directly from Crane (or through a Crane dealer) based on Crane's recommendation for your combination? If so, have you contacted Crane about what you saw on the dyno?

Or, dare I ask, was this a cam that someone had already and "this ought to work" determined why that's the one you used?

I'm starting to think Dwayne's suggestion that it might be cheaper and make more sense to change cams is good advice.

I think the next step would be to contact Crane and see if they can provide the .200 number.
It might help shed some light of the ramp speed of the cam.

Couldn’t hurt to get their recommendation for open/closed spring loads for the RPM you’re looking to turn, and see how it compares to what you’re running.

The bottom line is....... the cam may not be a very good match for the springs in that valvetrain combo.

It doesn’t sound like you tried revving it any higher.
It may just have a “fuss point” around 7k, and that it might have been okay higher up.

I understand the reasoning behind the current love affair with giant pushrods....... but I look at it as..........if you don’t need them...... it’s just extra weight the springs have to control. You only need what you need.
Imo, your pushrods are way way overkill for what’s in the rest of the valvetrain....... and there is extra weight there that I wouldn’t have added to that system.



Engine or chassis dyno?

FWIW, this is what my COMP RX measures:
Seat at .018" lash (.012" lobe) = 315
SAE duration at .018" lash (.016" lobe) = 307
.020 = 300
.050 = 266
.100 = 232
.200 = 184
.300 = 136
.400 = 68

Peak lift .434"

If you can get more data for your lobes, it's something in the same duration range to compare 'em to.

451RB, SR heads, steel valves, HS 1.5 rockers(measured closer to 1.55), Isky 9375/85 springs @ 250 closed, Comp RT .435 lobe, 302/272/193, 3/8” x.080” pushrods......... peak power at 7200, no indication of issues thru 7500.

The cam was specially ordered via Crane here in Australia.
The original spring pressure recommendations were 180-220 seat and 550-580 open. At the time I spoke them about the spring I had on PACs advertised figures and they gave me the green light. They said the pressures were a little higher than they would recommend, but that’s fine.

I contacted Crane direct at the their office in Olive Branch MS after this happened and the advice was to shim the spring more and after some more calculations I could yielding 280 seat and 640 open and 0.050” to coil bind measured with the retainer.

Im waiting here back from Crane about another issue I found with the cam but will have sit tight.

Their spring recommendation was 180-220 seat and 550-580 open on this cam. And I’m running in excess of that.
I kind of agree with what you are saying about the pushrods. Makes sense.
Should have listened to you and went the Comp .420 lobe.........too hard at the time and this was a comparable gentler lobe similar to that of the Comp.

This cam was not meant to be. First grind they sent me was on 1.100 base circle after I ordered a 1.050. And they ground 264/268@0.050 instead of 266/270@0.050 I ordered.
Apparently this was intentional as I was using a 0.815 roller wheel and this was done to compensate for that?? Might have to explain that one, I’m not sure.
But now I have found another manufacturing defect they are now looking at.
Never ends my friend!

If you wanted to do a test to see if it were more of “float” type of situation, or a spring “surge” situation, you could set up the current springs so they were pretty close to coil bind......... like .020-ish.
This changes to point of resonance, so if it’s a surge condition, it should make a noticeable difference.

I don’t think it would be enough of a pressure difference to add more than a couple hundred rpm to the usable range if the issue is really a spring load issue.

Of course....... the issue could be a little of both....... spring load, and surge.

The short answer is....... the bigger wheel adds some duration if the profile was designed around a smaller wheel.
The lobe design for a 1.050bc is probably done with a SBC in mind........ .750” wheel.
Using an .815 wheel on a .750 designed lobe generally adds 1-2deg@.050.

So I theory, those 264/268 lobes, if designed for a .750 wheel, would measure closer to 266/270 when checked using an .815 wheel.

I just received an email from Crane

Intake 183@.200
Exhaust 178@.200

It’s odd that if the two lobes are from the same lobe family, that the longer duration exhaust lobe(@.020 and .050) would have 5* less duration @.200 than the intake.

Or....... it’s a typo on their part(intake is 178/ex is 183)which would make more sense.

Either way, the .200 numbers aren’t anything unusual for that .050 number.

The Comp .420 lobe with 266@.050 is also 183@.200.

Looking through the Crane lobes..... since you’re having an upper rpm issue..... I’d get this:

LH2 series lobes:
R268/432 intake lobe(298/268/181, .432 lift)
R272/440 exhaust lobe(302/272/186, .440 lift)

Then test it before changing anything else in the valvetrain.