Schubeck lifters

[Dwight Southerland]

Originally Posted by Mike Taylor 3601

It isn't the spring pressure breaking parts,95% of valve train failures aren't from excessive spring pressure,they are caused by too low of spring pressure which lets lifter bounce and not follow cam lobe, which breaks ceramic lifters or axles out of roller lifters,pops the heads of valves,burrs keeper grooves, beats seats out wide,wears guides out, stretches timing chains, pops rocker studs and rockers in two.
Every lobe has a limit no matter how much spring you have there is a RPM which it becomes unstable and starts self destructing the valve train.

Larry may have just had lifter get fatigued or damaged some how and caused failure.
Mike Taylor 3601

Not exactly a complete analysis. While "not enough" valve spring pressure can cause failures as you describe because of lack of control, I would also have to say that the allowed increased spring pressure has promoted running the engines at a much higher rpm range and demanded much more radical camshaft dynamics which have contributed to more failures than not enough valve spring pressure. The stresses on valve train components increase geometrically with the rpm, which contributes to parts failure more than the "not enough" spring pressure as you point out. Also, without the increased spring pressure, having to resort to parts like the ceramic lifters or tool steel lifters would not have been necessary. The camshaft manufacturers are smart guys and will produce profiles that work with whatever pressures are available, so you think that they are not pushing the limits of design to take advantage of the increased pressures and increasing engine speeds and ramp events accordingly? They also pushed limits in the same way when we ran OEM valve spring pressure, but the spring pressure limitation kept the engine speeds lower and camshaft dynamics softer so parts were not stressed nearly as much. The snowball effect of the consequences of that one rule change has escalated the cost of stock eliminator more than any other, and it simply was not necessary.

[Billy Nees]

Originally Posted by Dwight Southerland

Not exactly a complete analysis. While "not enough" valve spring pressure can cause failures as you describe because of lack of control, I would also have to say that the allowed increased spring pressure has promoted running the engines at a much higher rpm range and demanded much more radical camshaft dynamics which have contributed to more failures than not enough valve spring pressure. The stresses on valve train components increase geometrically with the rpm, which contributes to parts failure more than the "not enough" spring pressure as you point out. Also, without the increased spring pressure, having to resort to parts like the ceramic lifters or tool steel lifters would not have been necessary. The camshaft manufacturers are smart guys and will produce profiles that work with whatever pressures are available, so you think that they are not pushing the limits of design to take advantage of the increased pressures and increasing engine speeds and ramp events accordingly? They also pushed limits in the same way when we ran OEM valve spring pressure, but the spring pressure limitation kept the engine speeds lower and camshaft dynamics softer so parts were not stressed nearly as much. The snowball effect of the consequences of that one rule change has escalated the cost of stock eliminator more than any other, and it simply was not necessary.

Hooray!!!!!!!

[Dan Lattimore]

Thank you ! Mr. Southerland

[SSDiv6]

Originally Posted by Dwight Southerland

Not exactly a complete analysis. While "not enough" valve spring pressure can cause failures as you describe because of lack of control, I would also have to say that the allowed increased spring pressure has promoted running the engines at a much higher rpm range and demanded much more radical camshaft dynamics which have contributed to more failures than not enough valve spring pressure. The stresses on valve train components increase geometrically with the rpm, which contributes to parts failure more than the "not enough" spring pressure as you point out. Also, without the increased spring pressure, having to resort to parts like the ceramic lifters or tool steel lifters would not have been necessary. The camshaft manufacturers are smart guys and will produce profiles that work with whatever pressures are available, so you think that they are not pushing the limits of design to take advantage of the increased pressures and increasing engine speeds and ramp events accordingly? They also pushed limits in the same way when we ran OEM valve spring pressure, but the spring pressure limitation kept the engine speeds lower and camshaft dynamics softer so parts were not stressed nearly as much. The snowball effect of the consequences of that one rule change has escalated the cost of stock eliminator more than any other, and it simply was not necessary.

Dwight is correct.

[JHeath]

Exactly, Dwight !!!!!!!!!!!!

[Dan Fahey]

Thanks Dwight.
I am not having valve train fracture problems in Pure Stock.
Basically early Stock rules.
IMHO be a good idea to moderate the spring rule.
Get back to a NTE rating.
NASCAR cams are a different breed.
Stocker cams are physically smaller.
Shorter lift and massive duration never intended.
150 lb closed and 400 open is a good start.
Some ratio for Valve size.

Just putting it out there.
D

[Mike Taylor 3601]

I agree if stock pressure spring rule was left alone in 87 wouldn't need tool steel,ceramic lifters and everything that came after that,was just putting out there the effects of not having the spring pressure to control the valvetrain, if you want to run the aggressive lobes and crank up the RPM then you have to have the spring pressure.
The stockers I build have plenty of spring pressure,they make more runs and require less maintenance than my pure stocker with stock spring pressure does,there valves,guides,spings,valve jobs will last twice as many runs as my pure stocker does..
Mike Taylor 3601

[Dwight Southerland]

Originally Posted by Mike Taylor 3601

The stockers I build have plenty of spring pressure,they make more runs and require less maintenance than my pure stocker with stock spring pressure does,there valves,guides,spings,valve jobs will last twice as many runs as my pure stocker does..
Mike Taylor 3601

Not to pick on you or be confrontive, but I raced a '67 Z28 Camaro on stock spec valve springs for four years, set three national records, won one national event, two points races, class at national events eleven times, logged over 300 runs, and broke one pushrod and one rocker arm. Shifted between 7000-7200 and cleared the lights at 7500. Then I raced an A-B/Stock 396-375 with stock valve springs for four years, set five national records, won class 13 times, quarter finals at three national events, and broke one retainer and shattered two keepers, shifting between 6800-7200 and 7400 in the lights. Before all that, I raced various 283-220 equipped rides with stock valve springs for six years, set umpteen records, won many races, logged over 1200 runs. Broke one retainer, one lifter while leaving the the starting line as high as 8300 rpm, shifting at 6800-7000 and at least 7000 in the lights. Then I raced an SS/C 427 Corvette that had Billy Badass valve springs, roller lifters, Jesel, etc. etc. In 87 runs I broke multiple lifters, pushrods, valve springs and rocker arms. Left the line at 7500, shifted between 7200 and 7600, and ran 8300 in the lights. So my experience tells me the obvious.

[Dan Fahey]

Hmmm interesting..
Moderating Spring Pressure is a good answer.
I like racing..not fixing broken stuff.
Using super high springs pressure creates larger catastrophic messes.

Someone mentioned they could not even get it off the Dyno.
Then required a new rotating assembly.

This does not happen anywhere often with Bracket Engines.

xHRA's need consider this.
Especially the RIO..
Fewer breakdowns during qualifying and competition.

D