They're offered with 2 different springs, one is labeled for hydraulic cams, the other for solid rollers. The rates are:
1.46" spring, 120# installed, 1.90" height, 394# open at 1.175", 390# rate
1.55" spring, 135# installed, 1.95" height, 430# open at 1.25", 420# rate
Nick
For info, if you have the heads setup for 1.90" seat height, the "roller" springs will be about 155# on the seat and 400# open.
IMO, that is fine for the MP 0.590" cam. Any flat tappet will have increased risk of lobe wiping as the spring pressures go up, and that is getting up there. I have run 150/440 but with EDM oil hole lifters, good oil, lots of care, and accepting the risk. But it is hard to recommend 440# open to others. So, 140-150 and 390-400 is my 2-cents.
