Why did nhra change the cam and valve spring rule in 1985? - Page 3

X-TECH MAN · 07-02-2010, 07:04 AM

While there are some comments about the older Jr. stockers on this site I had a flash back. Why did the rule change on cams and valve springs come about? Was it the lack of qualified people to do the job? Was it to much work? Do any of the older guys remember and know WHY? I can understand the duration and overlap being a pain to check and enforce but why didnt they just put a limit on the valve spring pressure of about 125-150 lbs seat pressure and 300-350 lbs open pressures across the board for all brands and types of engines? Easy to check while the head was removed for tear downs. This unlimited spring pressure rule is the primary reason you have to spend $700 to $900 on flat tappet lifters. Sleved lifter bores. It is also the reason for cut down crank pins, aftermarket rods, AND cheated up cylinder heads (air flow at higher RPM's) and intake manifolds. The valve springs most are running in "stock" today have more pressure than my old SS/IA Camaro had with an almost .700 lift roller cam and UNPORTED HEADS back in 1977-78. Mark, Woodro, or anyone have the answer from the good ole days of less expensive stockers????

07-02-2010, 07:04 AM	#1
X-TECH MAN Banned Join Date: Dec 2007 Location: Lake Placid, Florida Posts: 3,203 Likes: 1,047 Liked 235 Times in 110 Posts	Why did nhra change the cam and valve spring rule in 1985? While there are some comments about the older Jr. stockers on this site I had a flash back. Why did the rule change on cams and valve springs come about? Was it the lack of qualified people to do the job? Was it to much work? Do any of the older guys remember and know WHY? I can understand the duration and overlap being a pain to check and enforce but why didnt they just put a limit on the valve spring pressure of about 125-150 lbs seat pressure and 300-350 lbs open pressures across the board for all brands and types of engines? Easy to check while the head was removed for tear downs. This unlimited spring pressure rule is the primary reason you have to spend $700 to $900 on flat tappet lifters. Sleved lifter bores. It is also the reason for cut down crank pins, aftermarket rods, AND cheated up cylinder heads (air flow at higher RPM's) and intake manifolds. The valve springs most are running in "stock" today have more pressure than my old SS/IA Camaro had with an almost .700 lift roller cam and UNPORTED HEADS back in 1977-78. Mark, Woodro, or anyone have the answer from the good ole days of less expensive stockers???? Last edited by X-TECH MAN; 07-02-2010 at 07:16 AM.