Nice work on the website! Ne1 familiar with Erson "variable duration" lifters?
 

Any stangers runnin' the Erson "variable duration" lifters. Their ad claims that you can run big cams that still idle and pull good vacuum.

This may not answer your question about erson ones but here it goes. I have the road variable duration lifters. They seem to work for the most part if you can live with the noise they make. Kinda sounds like un adjusted lifters. I'm think about switching to the crane variable duration ones. They say they don't produce anytype of noise. Probably get them in april.

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67'fastback- Edelbrock carb, intake, cam, valve springs. Road lifters, Comp Cam rocker arms, windage tray, cerama coated headers, dual flows with H-pipe, modded c-4, tci stall converter, perma cool electric fan, aluminum water pump, griffen aluminum radiator, accel 8.8 cable, wide cap distriburator, magnetic pick up, manley valves, v-matic hurst shifter, edelbrock performer nitrous, carter electric fuel pump, ignitor coil, solid motor mounts, magna racing suspension, poly urathane bushings, und

I dunno about the Erson variable duration lifters, but they should all work the same...with the same fundamentals. When at idle there won't be as much lift given by the lifters so you'll idle better with more vacuum. As the rpms increase so does the pressure in the lifters and you've got the full cam lift. That's a really crude description though...perhaps someone else can explain it better.

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1984 1/2 GT350 (#842 Hatchback w/ T-tops), 302HO, Comp cams Xtreme Energy cam, Carter 625cfm carb, Weiand Stealth intake, MSD distributor, MSD coil, FMS 9mm wires, 1 5/8" MAC unequal shorties, 2 1/2" MAC Prochamber H-pipe, Flowmaster 2 chambers, KYBs, 16"x8" 4 lug Cobra Rs, Falken 245/45ZR16s