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

[X-TECH MAN]

Originally Posted by art leong

That would take all the street Hemi's and send them to the old cars home. The stock ( as came on the car) springs are higher than that.
They already have Super Chevy races Do you want to make them all that way?

The 69,70, 71 Street Hemi had single springs with a damper at 150 lbs on the seat and 320 open pressure specs. I have my old NHRA/IHRA engine spec book right in front of me as I type this. The 68 Street Hemi had 131 lbs on the seat and 280 open. The 66-67 Street Hemis had dual springs with the rating of 114 lbs outer and 53 lbs for the inner spring on the seat with 189 lbs outer seat pressure and 96 lbs for the inner open pressures (add them together) with solid lifters.The 68 and 69s had solid lifters also while the 70, 71s had hyd. lifters. The 68-71 had single springs with a damper. This was good for 7000 RPM operation. The street Hemis with an OEM oiling sytems and pans dont take to kindly to 8200+ RPM shift points for very long. I would think most all of the brand of engine combos would be OK with 150 lbs seat pressure and about 320 to 350 lbs open pressures unless they are running a cam with square lobes on it. By the way the 1969 440 six pack had a 150/320 lb pressure spec also.

[art leong]

Originally Posted by X-TECH MAN

The 69,70, 71 Street Hemi had 150 lbs on the seat and 320 open pressure specs. I have my old NHRA/IHRA engine spec book right in front of me as I type this. The 68 Street Hemi had 131 lbs on the seat and 280 open. The 66-67 Street Hemis had dual springs with the rating of 114 lbs outer and 53 lbs for the inner spring on the seat with 189 lbs outer seat pressure and 96 lbs for the inner open pressures with solid lifters.The 68 and 69s had solid lifters also while the 70, 71s had hyd. lifters. The 68-71 had single springs with a damper. This was good for 7000 RPM operation. The street Hemis with an OEM oiling sytems and pans dont take to kindly to 8200+ RPM shift points for very long. I would think most would be OK with 150 lbs seat pressure and about 320 to 350 lbs open pressures unless they are running a cam with square lobes on it. The 440 six pack had a 150/320 lb pressure spec also in 1969.

I thought it was 180 on the seat. The memory is the second thing to go LOL.
I know it was critical. We would set up a motor with stock valve springs put it together and reve it in to 7500 a couple of times. Then pull the heads and change the valves and springs. It was legal to put notches in the piston as long as the motor did it not the machine shop.

PS we shifted at 7200 when we were trying to go fast. The only time the motor would go any higher was in the water (once in a while)

[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.

[Billy Nees]

[QUOTE=X-TECH MAN;195800] I think 150/350 lbs would handle just about any current stocker running today

That's about "entry level"today! I'm running that on my 6 cylinder! Even if you made it 170 or 180 it would help!

[Ed Fernandez]

This topic is very amusing to me.I think that the standard shold be 130#/350# as my springs meet the parameters.Does this mean that all those intimidating ABC cars are
going to be slower bearing down on little old me?
I think if it can be proven that the seat pressure is higher than 130#/350# from the factory then that should be the standard for that combo.
Bill,nice comeback.

[X-TECH MAN]

Originally Posted by Ed Fernandez

This topic is very amusing to me.I think that the standard shold be 130#/350# as my springs meet the parameters.Does this mean that all those intimidating ABC cars are
going to be slower bearing down on little old me?
I think if it can be proven that the seat pressure is higher than 130#/350# from the factory then that should be the standard for that combo.
Bill,nice comeback.

I dont know how hard the blown Mustangs turn their combos and what kind of spring pressures they use but maybe they would only blow by you at 145 MPH instead of over 150+ MPH.......LOL.

[Billy Nees]

Originally Posted by X-TECH MAN

I dont know how hard the blown Mustangs turn their combos and what kind of spring pressures they use but maybe they would only blow by you at 145 MPH instead of over 150+ MPH.......LOL.

OHC engines use very little valve spring pressure. They don't need it.

[X-TECH MAN]

[QUOTE=Billy Nees;195806]

Originally Posted by X-TECH MAN

I think 150/350 lbs would handle just about any current stocker running today

That's about "entry level"today! I'm running that on my 6 cylinder! Even if you made it 170 or 180 it would help!

Its nice to day dream and BS about it but what does it take to get it done? I dont have any "pull" anymore and NHRA wont listen to anyone or their own committie so what can you do? Build your combo with the lower valve spring pressures to make it less expensive, get more runs and run slower or just keep on spending the big bucks for the trick of the week, rebuilding them every 75 to 100 runs and/or blowing up very expensive engines I guess.

[Billy Nees]

Take away an engines ability to rev and it will be less likely to hurt itself. NHRA is looking for ways to cut down on "down time" so it would seem to just be a common sense rule. BUT I did say NHRA and common sense in the same sentence didn't I? Isn't that like saying Military Intelligence?

[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.