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I'm rebuilding my 2276 as a turbo motor. CB 2288 cam (= K8), VW650 springs.
During mock-up, while turning the motor over by hand with pushrods on the #1 cylinder, one of them bent badly. These are CB's HD aluminum PRs (but not the dual-tapered ones). Looking at the CB website, I see now that these PRs are not recommended for use with VW650 springs. Fair enough; my bad.

There is no such warning with the DUAL TAPERED aluminum PRs (which cost twice as much). Has anyone used them with really heavy springs? Any issues?
The non-tapered HD alum. are 3/8 inch diameter.
The tapered ones are 3/8 in the middle, and SMALLER at the ends. Can these be stronger, somehow? Way back when John Conolly developed the dual-tapered aluminum PRs, he claimed they were extremely strong. But I don't know if CB's design is the same.

Why am I not addressing this question to CB directly? Because they have great products, but often give conflicting information, depending on who you talk to. (I suppose that is to be expected.)
Any actual experience out there? I'm trying to keep this motor quiet, if I can, but will run CR pushrods if I have to.

While we're on the topic of noise: one engine builder thought I would be OK running helical-cut cam gears with this setup, if they are aluminum (rather than magnesium), as long as I have dual-thrust cam bearings. Any dissents on this?

CB catalog says HD aluminium pushrods ok for up to 400lbs of spring & Dual tapered are okay for over 400lbs.

With that much spring force (~430ish) you maybe better with steel?

On the cam gear point. I dry built an engine recently with an aftermarket aluminium cam gear. There was a burr on the crank gear I missed and it chewed up the soft aluminium. I fitted a harder stock mag gear instead (drilled & counter bored)

I see now that CB has changed the descriptions in the online catalogue since I talked to Mark Lawless on Monday (and probably as a result of that conversation), adding "up to 400 lbs" for the non-tapered and "over 400" for the tapered. How much over is not specified. The 650 springs are said to give 420 lbs at .630 lift. My cam is lifting about .550 (actual measurement) with my 1.46 ratio rockers, so I should be under 420 lbs. I'd have to remove a spring and put it in a tester to know exactly how much under. I don't relish the thought of trying to remove these stiff buggers with my bench-mount spring compressor. (I had my machinist, the venerable Ken Jansen, use his hydraulic compressor to install them.)

As for cam gears, the interwebs is telling me aluminum is harder than magnesium. But also, I do seem to have more gear lash with this alum gear than I did in my last build, which was only about 1,500 miles ago. (The motor inhaled a steel washer somehow.)

No idea what alloy of magnesium the stock gear is made of, but it’s harder than a mag crankcase. I suspect the stock gears are more likely to crack (more brittle) than the aluminium “cheese” gears. That’s the typical trade off for soft-to-hard metals.

With those monster springs I’d personally be looking at steel gears but that’s way deeper than any build of mine, so I’m not speaking from experience.

If you’re running 650 springs you’re deep into straight-cut gear territory..

I used dual taper ali pushrods with VW650 springs with an 86B and the pushrods worked well. They were the aircooled.net ones.
I had a set of Magnum ali on steel straightcuts, but I chickened out on using them and went with the steel on steel.