I have a pair of original '69 Z28 heads ('186') at the cylinder head shop for rework... cleaning, magnafluxing, pressure testing, new guides, new valves, springs, etc. Everything is ready for assembly now, but the shop today told me that they seldom used the 'double springs' (with the damper inside) anymore; instead they typically use a single 'conical spring'... supposedly smaller diameter at the top than at the bottom?
I'm open to improvements, but I hate to change a good thing without understanding 'why'...
Do any of you have experience or knowledge of this spring type? And is it a good idea for a Z28/302 that I plan to rev towards 7000 rpm.... The company this shop uses is SBI (Nashville TN) for guides, valves, springs... They will inistall whatever I want to pay for... Any advice offered is welcomed.