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

[Dwight Southerland]

Originally Posted by X-TECH MAN

Just to remind some of you guys the 1969 396/375 and the 427/425 used a single valve spring with damper that had 106 lbs on the seat and 327 lbs open before the 1985 rule change. The max wedge was less than the street Hemi and the Chevy. The 428 CJs really sucked at 97 lbs seat pressure and 298 lbs open. I think 150/350 lbs would handle just about any current stocker running today and the expensive flat tappet lifters would no longer be needed. A new rear gear might be required for those who delite in slinging the snot out of their combos.....lol.

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.