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.