This is the top-of-the-line dual spring set up for engines designed to rev up to 8500rpm. The VW650 valve springs drop-in to heads machined for VW diameter dual springs.
The VW650 springs are designed for extreme endurance so a Nascar grade proprietary material that has unsurpassed high cycle fatigue life is used. These springs have extensive surface finishing including nitriding, polishing, heat set, and a micro shot peen. For the strip or street, the VW650 valve spring will hold up to the most demanding driver.
Installed height of 1.540'' gives you @ 160 lbs. of seat pressure, and @ .630'' lift you have an open load of 420 lbs. With the VW650 valve springs you can run up to .630 lift.