With regard to application: those OEM engines are designed more for cost and emissions than anything else these days. The performance is almost a side effect. Almost.
These modern engines run ring packs most hot rodders wouldn't consider, much lighter/thinner pistons, have better valvetrain geometry, and have a lifter/pushrod/valve package that's extremely well engineered due to the sheer volume of production and the manhours available to put into durability and abuse testing. The use of BH springs goes hand-in-hand with those other choices/constraints and is likely driven by cost as much as anything. A BH spring is going to use less metal than any single spring with a damper, or double or triple spring package, and the cost of the metal is what you get in commodity parts. The volume negates almost all the engineering and development costs, and automation nearly eliminates labor costs.
Modern heads and induction are also so good that most engines don't need the super radical cams that oldschool iron does - and thus can better control the valves with less force - which starts what an old boss of mine would call: "ever decreasing circles to the left until you fly up your own ***". By that I mean the lower force allows the designer to thin the valve stem, which then further reduces mass and required force, then the retainer can be thinned, and then the spring can be reduced in diameter, and then a BH profile can be used because narrowing one end of a spring is nearly free in a coiler and results in an even lighter retainer... In the end, you wind up with a very well engineered system that happens to use BH or conical because it was designed to - not because BH or conicals offer intrinsic benefits in and of themselves.
Making the change from a cylindrical spring to BH or conicals also comes with bigger implications than just resonance or surge or mass. The rate of the spring is no longer linear, and so becomes a much more involved engineering problem that the typical builder or hot rodder isn't going to have the ability to suss out. There's also decades of knowledge behind most enthusiast engines with regard to spring rates needed for certain cam specs. If the springs become non linear, and old assumptions are broken down, one is left with a recipe for disaster because seat/nose loads are no longer sufficient to describe a proper spring. Now you need an @.050 spring load too... or maybe @.200 - or does it matter more @ .500?
That doesn't mean they don't have their place, but the benefits only tend to matter in specialty use cases. Typically OEM applications or super-scienced out builds that need very minimal valvetrain weight, and in those cases the cam is going to have to be designed to work with the valvespring and valvetrain package as much as it is for the timing events.
It's a complex topic, and it seems like RB is only trying to point out that painting BH, or conical, or cylindrical springs with a broad brush as to their benefits and drawbacks is the wrong way to go about it because they all exist for different reasons and tend to operate under vastly different constraints/applications. Which I think Dale is also saying.
So in effect, ya'll are arguing about how much you agree with one another.
:rofl:
