increased seat pressure helps with keeping the engine together at high RPM. there's a lot of inertia in those heavy hydraulic roller lifters, and too light of a seat pressure could cause the lifters to bounce when the valve closes at high RPM, causing loss of cyl pressure, and risking damage to the lifter and cam.,
Dave was using the GM springs.
to figure out new lift, take the old lift #, and multiply by 1.0667 (1.6/1.5)
If you want to run the GM springs with mag heads, get your cam reground by bulletcams.com. talk to Tim. I'd use their HR262/300 lobe for both the intake and exhaust. it's 262 adv,
210@.050 lobe lift,
124@.2" lobe lift and .3" lobe lift, which calculates to .480" valve lift. just have them use the stock LSA and ICL that's ground on the cam (the LA's is 112 LSA, 108ICL)
it's slightly less aggressive than the lobe I'm using, their HR259/316 lobe (259 adv,
208@.050,
127@.2, .316" lobe lift), but should give similar performance, which in my mag headed 318 is very healthy.
if you wanted a lumpier idle, and something that is more in the 2200-6500 RPM poweband vs. the idle-5500 RPM powerband that the above cam would give, I'd look at their HR279/288 or HR276/300 lobe.
http://bulletcams.com/Masters/HRlobes.htmregrind price is $150, and it's about $12-15 each way to ship the cam. one tip, what works good for shipping the cam is a chunk of 3" OD PVC pipe, a glue on PVC cap on 1 end, and a PVC cleanout on the other. wrap the cam in bubblewrap and slide it in.
