What valve springs did you use with your Isky E-4?

No hands on here Mike, but I can't believe you'd really need a dual spring in that application with a fairly mild ramp cam and the lightweight of the small valves.....unless it for a big rpm race application.

The 901 comp's spec at 104 seat/259@1.25 height, and a 387lb rate.
I'd personally would have no problem running those on a engine that didn't require "max" rpm's.

For a serious 273 build, I still think a single could get the job done even with a larger "milder" ramp cam. If I was going to step up. I think the Crane 99835 with a 113 seat/280@1.25, and a 412 rate, should cover what's needed for any hot street/bracket engine.

Just my thoughts...