CLASS RACER FORUM - Why did nhra change the cam and valve spring rule in 1985?

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

[QUOTE=Billy Nees;195806]

Quote:

Originally Posted by X-TECH MAN (Post 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!

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.

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

Quote:

Originally Posted by Ed Fernandez (Post 195812)

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.

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

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?

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

Quote:

Originally Posted by X-TECH MAN (Post 195815)

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.

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

Quote:

Originally Posted by X-TECH MAN (Post 195800)

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.

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

Quote:

Originally Posted by Dwight Southerland (Post 196005)

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.

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

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.

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

Quote:

Originally Posted by Billy Nees (Post 196013)

It might make some of the "square" cams unusable but a max spring pressure rule would put everyone in the same boat and keep more engines in one piece. Less chance for a broken bouncing valve destroying an engine and maybe less chance of being forced to run a diaper in the near future. Not only the "SQUARE" cams but what about some of the 55mm cams I have been hearing about in stock. I wouldnt think they would be legal but they are out there. Ramblings of an old retired foolish dumb tech guy living in the flat part of Florida.

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

Terry, You need something to do.......I know, you can join the hunt for the 25 foot python seen in your driveway last month. Billy Chupacabra was seen in the area of your Hilly home, be careful at nite they sniff out empty beer bottles left about.

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

Yeah...Im bored. I already shot a snake in my yard a couple of weeks ago.