What Powell claims is similar to HioSSilver. SDPC also says that spring rating of .550 to .570 (LS6 spring) is fine to use on a .550 lift cam. I've always heard that is too close, especially with a M6 car that could overrev on a mishift.

 

I agree with you. Ill also say that the factory rev limter is very slow to react, because it cuts fuel, rather than shorting the ignition. There are tolerances that also need to taken into consideration. If I were running a .550" lift cam, I'd also be running springs that were good to .600" lift. I once had a dual spring setup save me when the outer spring broke, so I like the somewhat better "insurance" duals offer. For me, a guy that puts at least 5,000 miles yearly on my engine, running a .550"-.570" spring on a .550" lift lobe is probably asking for long term reliability issues. Of course you'd have to measure everything closely before assembly. Who is SCDP? I've never heard of them. Are you meaning Scoggin Dickey, SDPC? If so, they have one of the best engine builders in the country working there. That would be one Kurt Urban. At least, he was still there last I knew. But it still comes down to how you use the car, your vision of low maintenance, and mileage between spring changes. Oil temps are HUGE when it comes to spring life. I ran 1905 PAC duals for just over 50,000 miles on a .600" lift cam. Everyone here scoffed at that. They said the springs had lost tension.....Until I had Tony Mamo check them, and all 16 springs checked out good. Even Tony figured at least some would be out of spec. A big part of that is I ran a B&M 70266 oil cooler, and had it in a great position for airflow. Seldom did my oil temps top 200°. Usually 195°-200°. Oil is basically the only cooling valvesprings get.....

 

Scoggin Dickey Performance. I mistyped the letters.