Norris HD Dual Valve Springs MADE IN USA
There comes a point where a single valve spring, even with a dampener, will not keet a lifter aginst a cam, the valve from bouncing, etc. It is at this point where dual HD Hi-Rev valve springs are necessary. As mentioned in the Single Spring specs, it is imperative that the valve train be kept tight to prevent a catastrophe. Norris recommends dual springs be installed for many applications where high valve lift, a steep ramp angle, higher RPM operation is desited; a heavy valve lifter and push rod weights are used, etc. Many top builders recommend dual springs for almost any performance application. However, as mentioned before, there is a right time to use them. Norris was one of the first companies to recommend the use of dual springs for VW applications, and one ove the first to develop the technology to implement them... ALMOST 50 YEARS AGO.
Our dual springs test at 130 lbs at 1.55" installed spring height. These can be shimmed to the appropriate level to match the desired compression tension, valve weight, and RPM range by adding spring shims underneath them, which are also available. These springs are manufactured a hair on the lighter side compared to many aftermarket springs to allow them to be shimmed and adjusted properly to avoid having too much spring pressure (lost horsepower and more wear) for your application.
These will require machining by a skilled machines to cut the valve guide boss properly to allow for proper installation without coil bind. It's impossible to make a blanket statement to tell when they should be used, but youre engine (head) builder should be able to make the recommendations for you. If not, we'd be more than happy to help. Just drop us an email or give us a call. Proudly MADE IN USA.