I've got new heads coming. The supplied springs are Comp 987-16.
Specs: 121 lbs @ 1.8", 343 lbs @ 1.2". (370 lbs/in)
I also have Comp 26918 (Beehive).
Specs: 125 lbs @ 1.8", 348 @ 1.2" (372 lbs/in)
While the spring rates are almost identical, the question comes down to valve train control and rpm. I'm staying with my .535"/.544" cam (using 1.6 rockers). I'm using the Beehive springs in the current setup and have bounced off 7 grand a couple of times with no ill effects (other than scaring the crap out of me!)
What are the limitations going to be with the heavier 987 spring and retainer? I shift at 6500 (1st -2nd) and 6000 (2nd -3rd).
The last thing I want to do is float a valve into a piston.
Any experiences out there? They're both very common springs so I figure somebody has some hard data.
Thanks.

 

The beehives and their much smaller retainers shave a fair bit of weight off the valvetain where it counts most- the valve side. Weight is the enemy of RPMs. And their design is inherently better at reducing spring harmonics (it isn't a single diameter the entire length). Much of the time they don't require as much pressure to get the job done as a standard spring for those reasons (and probably othe reasons that are beyond my knowlege). But they are more expensive (the downside).

If you got 'em why not keep using 'em?

 

All of what you've said is true.
As it turns out, there's a comprehensive test comparison (between these two exact springs) done by David Vizard and Comp Cams.
The Beehive is the hands down winner. Valve control is extended by several hundred rpm and this is in an range that has resonable applications. In a cam with .544 lift the conventional spring became unstable at 5500 rpm and a final crash at 5700. The Beehive doesn't lose control until 6750 rpm.
While I do have a set of 26918's, they're installed in my Vortecs and I'd like to keep them complete. Looks like that won't be the case.