Do you know how close you where to coil bind? It looks like they wanted .750 lift max with those specs Give them a call to make sure I just check some 1.550 PACS that I bought for a project, around twenty dyno pulls and warming the motor up several times, no loss of pressure at all 290 lbs. on the seat and close to 800 lbs opened at .700 lift That is .060 from coil bind I didn't check all the valve lifts at the retainers when I assemble that motor, I only checked the passenger side with these springs so I'm going to check the dirvers side as soon as I put that head back on. I had a leaky(6to7%) exhaust valve on the after dyno leak down test It turned out that it had a slight bit of rust on that valve seat, I removed it with scotchbrite and it sealed right up Lucky me I had to haul the motor 50 miles to the dyno in the back of my pickup and back in very humid, cold weather. I used paper towels and duct tape to seal the exhaust up but stuff happens any ways BTW, I'm impressed with those PAC springs