Why did nhra change the cam and valve spring rule in 1985?

[X-TECH MAN]

Originally Posted by Dwight Southerland

And all SBC combos from 1967-1991 used 84 lbs on the seat and 206 lbs @ .450" compression. NHRA allowed an additional 10 lbs on the seat and 20 lbs open for a dampener, if the factory specs called for one.

I remember when I got my brand new 68 Z-28 I could sling it to 7000 RPM easy and I never had the valve covers off yet to shim the springs and lash the valves. The springs had to be around 70 lbs on the seat or close to it. I did pull 4 studs (68s had pressed in studs) one evening (car was 2 days old) due to a missed shift with the OEM clutch sticking to the floor at 7000......lol. Probably lucky I still have my legs as I still had the OEM cast flywheel and no scatter shield yet. Dumb ***** attack on my part.