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

[SSDiv6]

Originally Posted by Billy Nees

The trouble with setting a specific # for valve springs in this day and age is that the cam manufacturers are building cams that a flat tappet lifter just can't follow even with the best springs! I believe that some of the really sharp Stocker engine builders are actually getting away from "square" cams and going back to "softer" lobes at least on the exhaust as they're finding they're "cleaning up" the intake charge by not bouncing the exhaust valve around on the seat. Think about what the "harmonics" of that exhaust valve bouncing on the seat is doing to the intake charge not to mention the cylinder pressure.
Another good reason for "softening" the lobe is simply to use less spring. Heavy springs just "tie up" horsepower that can't be used to accelerate the vehicle.
I guess where I'm going with this is that as much as I'd like to see a "valve spring spec" rule put in the book it would make a lot of cams in use today unuseable and I don't forsee any of todays Stocker engine builders or cam manufacturers lobbying for a rule that will make their stuff unuseable.
But these are just the ramblings of a bored, crazy old fool living on a hill in Pennsylvania.

Billy, there is a lot more in camshaft design and in the early days, it was mostly hit/miss. Camshaft technology has taken great leaps with the advent of computer modeling.

In the early days when cams were checked and with the early spring rules, cams where still being designed and built with "Dwell" lobes or what many call square lobes. Let's not forget the days when many ran General Kinetics Cheater cams. Almost all of Don's cam designs were dwell lobes. The cam manufacturers of the early days for cheater cams were General Kinetics, Lunati, Cam Dynamics and Eonics. Later on, other companies such as Crane, Isky and Comp Cams joined the fray when the spring rule changed. In the early days, if you had a Chevy, you ran Lunati; if you had a Mopar, you ran a GK cam; if you had a Ford, Cam Dynamics, if you had an Oldsmobile or Pontiac, you ran an Eonics cam.

Although there were spring pressure limits in the early days, the specification sheets sent by the manufacturers were quite liberal especially with Mopar.

The big difference on the new generation Cheater camshaft is they have faster ramps with bigger numbers in 0.200" lift area.

[Billy Nees]

Originally Posted by SSDiv6

Billy, there is a lot more in camshaft design and in the early days, it was mostly hit/miss. Camshaft technology has taken great leaps with the advent of computer modeling.



The big difference on the new generation Cheater camshaft is they have faster ramps with bigger numbers in 0.200" lift area.

I agree with you completely that with the advent of "CAD" camshafts there have been great strides in "Stocker" performance potential BUT it is still at a cost! No matter where you increase the opening and closing rates on the cam the valve MUST follow the ramp and the rate of opening or closing. It still comes down to a compromise. When and where ever you increase the speed of the valve event you have to have a spring rate that will allow it to follow the lobe. So you will STILL need better lifters, pushrods, springs etc. to get the job done. And you still have to spin the motor accordingly.

[X-TECH MAN]

Originally Posted by Billy Nees

I agree with you completely that with the advent of "CAD" camshafts there have been great strides in "Stocker" performance potential BUT it is still at a cost! No matter where you increase the opening and closing rates on the cam the valve MUST follow the ramp and the rate of opening or closing. It still comes down to a compromise. When and where ever you increase the speed of the valve event you have to have a spring rate that will allow it to follow the lobe. So you will STILL need better lifters, pushrods, springs etc. to get the job done. And you still have to spin the motor accordingly.

Might as well build a Super Stocker. Roller lifters cost less, roller rockers are less prone to breakage, Your going to sling the snot out of the engine with the rules the way they are so use better stronger parts and the heads and intakes are ported anyway and probably cost less from not having to hide what you do to them......lol.

[SSDiv6]

Originally Posted by X-TECH MAN

Might as well build a Super Stocker. Roller lifters cost less, roller rockers are less prone to breakage, Your going to sling the snot out of the engine with the rules the way they are so use better stronger parts and the heads and intakes are ported anyway and probably cost less from not having to hide what you do to them......lol.

Under your premise, let's move the current Stockers to Super Stock, then bring back Modified Eliminator and move all current Super Stockers and finally bring back Pure Stock again. LOL!!!

[X-TECH MAN]

Originally Posted by SSDiv6

Under your premise, let's move the current Stockers to Super Stock, then bring back Modified Eliminator and move all current Super Stockers and finally bring back Pure Stock again. LOL!!!

LOL....Well the A/SA and AA/S are quicker than the Pro stocks were in 1970 (or the 1/4 mile is shorter) on little bitty 9 inch tires, "stock heads", OEM bottom ends, and they weigh more. Its called "Progress"

[cudadoug]

Originally Posted by X-TECH MAN

Might as well build a Super Stocker. Roller lifters cost less, roller rockers are less prone to breakage, Your going to sling the snot out of the engine with the rules the way they are so use better stronger parts and the heads and intakes are ported anyway and probably cost less from not having to hide what you do to them......lol.

Couldn't have said it better! While I'm not a "S/S or stocker racer", I do follow it pretty closely. There are quite a few stocker racers who DO believe a Super Stocker makes more $EN$E. Less cost, more contingency dough (IF you can paid!) and often less car counts...

I also believe that the valve spring rule was the turning point to begin the RUIN of the class and it's original concept.

[SSDiv6]

Originally Posted by X-TECH MAN

LOL....Well the A/SA and AA/S are quicker than the Pro stocks were in 1970 (or the 1/4 mile is shorter) on little bitty 9 inch tires, "stock heads", OEM bottom ends, and they weigh more. Its called "Progress"

I was watching some old movies in You Tube and suddenly realized that some of the lower class current Stock Eliminator cars are running faster than the old Modified Eliminator cars that had aluminum heads, tunnel rams and twin carbs!!!

[X-TECH MAN]

Originally Posted by SSDiv6

I was watching some old movies in You Tube and suddenly realized that some of the lower class current Stock Eliminator cars are running faster than the old Modified Eliminator cars that had aluminum heads, tunnel rams and twin carbs!!!

And what does that tell you? Its not all tire technology and ring packs....Maybe the air is better today than back in the 60's and 70's?

[Alan Roehrich]

Originally Posted by X-TECH MAN

And what does that tell you? Its not all tire technology and ring packs....Maybe the air is better today than back in the 60's and 70's?

It's any number of things. Granted valve springs have allowed a lot. But clutches, carburetors, torque converters, headers, and transmissions have come a long way. There's a ton of things that have gotten better, and racers have gotten smarter because there's more information available as well. Information and knowledge make a lot of HP.

[Rick Leininger Jr.]

Originally Posted by Billy Nees

No matter where you increase the opening and closing rates on the cam the valve MUST follow the ramp and the rate of opening or closing.

IF you use the ceramic lifters.