TECHNICAL FEA­TURE

RACING VALVE SPRINGS: SOUND RULES TO REMEMBER

Drag Racer - - CONTENTS - Ben Mozart PerTronix Per­for­mance Prod­ucts Archie Bos­man Moore Good Ink Text by Pho­tos Cour­tesy of Text by Pho­tos by

BE­FORE START­ING THIS VALVE SPRING STORY I THOUGHT I HAD A GRASP OF ITS MECHANICS, BUT THEN AS IT DE­VEL­OPED, IT BECAME INCREASINGLY COMPLICATED, UNTIL I REACHED A POINT WHERE I DOUBTED IF I HAD ANY IN­TU­ITIVE UNDERSTANDING OF HOW VALVE SPRINGS AND THEIR ATTENDANT VALVE GEAR FUNC­TION.

Hap­pily, the ac­cu­mu­lated reams of re­search data were sim­pli­fied when Dick Boyer en­tered the pic­ture. Here, cour­tesy of Er­son Cams, are sev­eral sound rules to remember. It’s a brief in­sight de­vel­oped for those in­ter­ested in high-per­for­mance en­gine tech­nol­ogy that ex­plains the sever­ity of the en­vi­ron­ment in which the valve spring op­er­ates and some of its re­la­tion­ships with the var­i­ous func­tions of the valve train.

Er­son sug­gests that the pri­mary fac­tors con­sid­ered when se­lect­ing valve springs in a racing en­gine are first, the amount of valve lift, and sec­ond, en­gine speeds. As en­gine speed in­creases, so does in­er­tia, which refers to valve-train re­sis­tance to changes in speed and di­rec­tion.

With re­gard to the valve when it is fully open—at max­i­mum valve lift—most en­gine builders de­sire the valve spring to be within 0.050 inch to 0.060 inch of coil bound. This al­most coil-bound con­di­tion re­turns the coil spring to a uni­form, sta­ble shape on ev­ery clos­ing cy­cle.

If not, the spring ex­hibits ex­ces­sive space be­tween the coils and it can­not main­tain its com­po­sure—it con­stantly shakes and wig­gles. There­fore, it could be ar­gued that a valve spring op­er­at­ing at mod­er­ate lift that doesn’t close prop­erly is more in­clined to ail with pre­ma­ture weak­ness or break­age than one op­er­at­ing with higher lift that does close prop­erly.

AGGRESSIVE CAMSHAFTS AND WHEN THEY UNDERMINE THE COM­BI­NA­TION

Beyond these two pa­ram­e­ters—the amount of valve lift and en­gine speeds—there is the ag­gres­sive­ness of the camshaft pro­file to con­sider. Race en­gine builders fre­quently re­fer to an aggressive lobe as a “square lobe,” which con­veys a some­what ex­ag­ger­ated men­tal pic­ture. “Ag­gres­sive­ness” in this con­text means how fast the valve is pro­pelled off the valve seat. If it’s too aggressive, at some point in the en­gine rev cy­cle it will loft the lifter off the cam lobe, and the val­ve­train as­sem­bly will lose con­trol. This is de­bil­i­tat­ing as it un­der­mines valve- spring longevity.

Race en­gine builder Jon Kaase warns, “When the valve-to-lifter as­sem­bly leaves the cam lobe on the open­ing side and comes crash­ing down on the clos­ing side, this af­fects the en­tire valve train, par­tic­u­larly valve springs. It weak­ens them and can break them. It also in­jures solid roller lifter wheels as it bangs them against the camshaft lobes.” Con­se­quently, overly aggressive cam profiles have a nul­li­fy­ing ef­fect, most no­tably when pis­ton speeds out­run the valve events.

SEAT PRESSURES

Springs are avail­able as sin­gles, dou­bles or triples, and they are se­lected by the amount of pres­sure re­quired for the lifter

It’s all about how hard you are push­ing the lim­its. If you use the same spring for the in­take and the ex­haust, which we of­ten do, the ex­haust will last longer be­cause it has more de­grees of du­ra­tion than the in­take. —Jon Kaase, race en­gine builder

to fol­low the cam lobe. Nat­u­rally, you use the light­est spring to con­trol the valve—that is, to keep it closed and not al­low it to chat­ter—be­cause the higher the spring pres­sure, the more power is ab­sorbed by the en­gine to op­er­ate it. If a sin­gle spring can con­trol the valve, adding more spring pres­sure will not gen­er­ate more power. On the other hand, cylin­der pres­sure will be lost if the valve chat­ters. Valve chat­ter or valve bounce means the valve con­tin­ues to bounce on the seat when it closes. Chat­ter is of­ten caused by in­suf­fi­cient valve-spring pres­sure or by the valve clos­ing too ag­gres­sively, de­spite, some­times, the lifter fol­low­ing the cam lobe faith­fully.

Seat pressures used with flat-tap­pet camshafts are usu­ally in the 120- to 140-pound range. How­ever, by em­ploy­ing care­ful run­ning-in pro­ce­dures with ex­pen­sive tool steel flat tap­pets and camshafts some en­gine builders adopt 200-pound seat pressures and beyond.

But on Kaase’s Boss

Nine hot rod en­gines, which use a hy­draulic roller camshaft and op­er­ate with sin­gle valve springs, the seat pres­sure is around

160 pounds. On its P-51 race en­gines, which run a solid roller cam and dou­ble springs, the seat pressures are 220 to 230 pounds. On the Moun­tain Mo­tor Pro Stock race en­gines, seat pressures are gen­er­ated by triple springs and main­tained in the 450-pound range. Valve spring open pressures on these en­gines op­er­ate at around 1,200 pounds.

Er­son’s Dick Boyer agrees that the worst thing you can do is to lose valve train con­trol due to in­suf­fi­cient spring pres­sure. The horse­power loss caused by adding a lit­tle more spring pres­sure is neg­li­gi­ble com­pared to the ef­fects of in­suf­fi­cient spring pres­sure, which will lead to fail­ure.

En­gine builder Kevin Stoa adds, “You could have the best valve in the world, but if it floats, it can act like a jack­ham­mer and break.” Of­ten, the good name of the valve maker is blem­ished when the fault lies in in­ad­e­quate spring pres­sure or the valve train go­ing out of con­trol. As a con­se­quence, the valve can be ham­mered, as Stoa in­di­cates, until it breaks.

WHAT’S VALVE FLOAT?

Valve float oc­curs when the valve train is out of con­trol. It’s when the lifters have lost con­tact with the lobes, when they no longer fol­low the cam. “If the valve train loses con­trol dur­ing a dy­namome­ter pull, it is au­di­ble,” says Stoa. In­stead of the air flow in­creas­ing or re­main­ing lin­ear, it de­creases pre­cip­i­tously. The loss is also ap­par­ent in the num­bers.

“The air­flow might be 800 cfm, but if it en­coun­ters valve float, it will in­stantly drop to, say, 500 cfm or 600 cfm. The fix is not al­ways sim­ple, but ini­tially, we might ex­per­i­ment by in­creas­ing valve spring pres­sure or re­duc­ing rocker arm ra­tio. Let’s say your rocker is 1.6:1, we might re­duce it to 1.5:1.”

Jon Kaase tells us, “It’s all about how hard you are push­ing the lim­its. If you use the same spring for the in­take and the ex­haust, which we of­ten do, the ex­haust will last longer be­cause it has more de­grees of du­ra­tion than the in­take.” Some­times Kaase uses a sim­i­lar cam lobe shape on both the in­take and the ex­haust. “When you do this, usu­ally the springs act about the same, ex­cept the in­take is usu­ally a lit­tle bit heav­ier, and so it might have a prob­lem a lit­tle bit ear­lier be­cause of the ad­di­tional weight.”

Of course, the spring not only closes the valve but also con­trols the rocker arm and pushrod mass. In ad­di­tion, if the racer de­mands greater en­gine speeds, greater lift re­quire­ments and the more aggressive camshaft lobes (faster and harsher), the heav­ier the valve spring must be.

Er­son Cams, widely viewed as a leader in competition camshafts, has been pro­vid­ing pro­pri­etary racing valves springs since the ’90s. De­signed for professional and sportsman racers, Er­son’s FSP se­ries is aimed at drag racing, oval track and en­durance events as well as mo­tor­cy­cles. These competition valve springs are cre­ated from su­per-clean, ul­tra-strong, specif­i­cally blended steel al­loy wire of the high­est qual­ity.

De­signed for professional and sportsman racers, Er­son’s FSP se­ries is aimed at drag racing, oval track and en­durance events as well as mo­tor­cy­cles. These competition valve springs are cre­ated from su­per-clean, ul­tra-strong, specif­i­cally blended steel al­loy wire of the high­est qual­ity.

If in­suf­fi­cient clear­ance ex­ists be­tween pocket wall and spring, ma­chine pocket with spring seat cut­ter to pre­vent bind­ing. By con­trast, ex­ces­sive clear­ance be­tween the pocket wall and spring pro­vokes un­wanted, ax­ial move­ment. Cor­rect the prob­lem by...

Most en­gine builders ar­range the valve spring to be within 0.050 inch to 0.060 inch of coil bound, which re­turns the spring to a uni­form, sta­ble shape on ev­ery clos­ing cy­cle.

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