My 99TA had about 30,000 miles when the heads and cam package was installed in 2002. Today the 99TA has 157,000+ miles with the same heads & cam package. The valve springs were last replaced in 2008 when the car had about 95,000 miles. The TA sees daily driver use and some fun from a roll on occasion but hasn't been to the drag strip in over ten years. Rev limiter is set at 6,800 rpm and I've hit it several times but normal shift point is 6,200 to 6,300 rpm. Very seldom does the car see 6,500+ rpm.
I know there are many good valve spring solution these days that are better than the 987 dual spring. I think TEA did fantastic building a 5.3 Stage 2 cylinder head that proved high quality and affordable. After 125,000 ÷ miles, I think it's proved the XER cam lobes are suitable for daily driver's with reasonable care and upkeep.
My TA was always allowed to fully warm up before seeing more than 3,000 rpm seldom saw more than 2,000 when warming up. Warm up was normal water temp on gage and oil pressure at normal for full warm up - typically 42 pounds for this car.
Thank you to Norris Motorsports for doing the new BTR Platinum valve spring kit install and saving my old valve springs and hardware. Likewise, I want to thank Land Speed cylinder heads for helping me get the old valve springs tested.
The 987 Springs held up as show below. The springs were disassembled, cleaned in a parts washer, rinsed, dried with compressed air and reassembled. They were tested using a seat and the height was taken into account. All 16 Springs were tested but not in any particular order.
Comp Cams states on their website new springs may have pressures vary by about 10 percent. 99 Black Bird's valve spring test results.
I will post some retainer and hardware pictures later.