Valve spring tech
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With the many choices of aftermarket cylinder heads, most with longer-than-stock length valves, the recommendation of a specific spring for a specific cam is almost impossible. It is now necessary to select the spring that will best fit the cylinder head configuration. We offer the following as general guidelines only: | With the many choices of aftermarket cylinder heads, most with longer-than-stock length valves, the recommendation of a specific spring for a specific cam is almost impossible. It is now necessary to select the spring that will best fit the cylinder head configuration. We offer the following as general guidelines only: | ||
| − | # | + | #Flat tappet street and street/strip '''seat''' pressures: |
| − | ##Small Block: 105-125# | + | ##Small Block: 105-125# seat pressure |
| − | ##Big Block: 115-130# | + | ##Big Block: 115-130# seat pressure. Big block applications need higher seat pressures due to their larger, heavier valves. |
| − | # | + | #Flat tappet street and street/strip '''open''' pressures: |
| + | ##Open pressures should not exceed 330# open pressure (sustained after spring break-in for acceptable cam and lifter life. | ||
##Open pressures should be a minimum of 220# for applications up to 4000 RPM. | ##Open pressures should be a minimum of 220# for applications up to 4000 RPM. | ||
| − | ##For good performance above 4000, open pressures should be at least 260# with stock weight valves. | + | ##For good performance above 4000, open pressures should be at least 260# with stock weight valves. Lightweight valves require less open spring pressure. |
| − | ## | + | ##Open spring pressures over 280# can cause pressed-in studs to come loose. Therefore, we recommend screw-in studs for open pressures above 280#. |
| − | # | + | #Hydraulic roller cams require higher seat pressures to control the heavier roller tappets and the more aggressive opening and closing rates available to roller cam profiles. |
| − | ##Small | + | ##Small block applications: 120-145# seat pressure |
| − | ##Big | + | ##Big block applications: 130-165# seat pressure |
| − | # | + | #Hydraulic roller cams require higher open pressures to control the high vertical opening inertia of the heavier roller lifters. |
| − | ##Small | + | ##Small block applications need at least 260# for general performance applications up to 4000 RPM. |
| − | ##Moderate performance small block applications like 300-360# open. | + | ##Moderate performance small block applications like 300-360# open spring pressure. |
##Serious small block applications can tolerate 400-425#* open pressures and still expect reasonable valve train life when top quality springs, pushrods, and lubricants are used. | ##Serious small block applications can tolerate 400-425#* open pressures and still expect reasonable valve train life when top quality springs, pushrods, and lubricants are used. | ||
| − | ##Big Block applications need at least 280# for general | + | ##Big Block applications need at least 280# for general performance applications up to 4000 RPM. |
| − | ##Moderate performance big block applications like 325-375# open pressure. | + | ##Moderate performance big block applications like 325-375# open spring pressure. |
##Serious big block performance applications can tolerate 450#* open pressure and still expect reasonable valve train life when top quality springs, pushrods, and lubricants are used.<br>Note: Open pressures in excess of 360# require the use of roller tappet bodies made of billet steel. Crane hydraulic roller and solid roller tappets are made from heat treated steel billet to withstand the stresses of high-performance use. Most stock hydraulic roller tappet bodies are made of cast iron and cannot tolerate high spring loads.<br> | ##Serious big block performance applications can tolerate 450#* open pressure and still expect reasonable valve train life when top quality springs, pushrods, and lubricants are used.<br>Note: Open pressures in excess of 360# require the use of roller tappet bodies made of billet steel. Crane hydraulic roller and solid roller tappets are made from heat treated steel billet to withstand the stresses of high-performance use. Most stock hydraulic roller tappet bodies are made of cast iron and cannot tolerate high spring loads.<br> | ||
| − | # | + | #Mechanical roller cam and lifters are generally used in serious street/strip and full competition applications. Mostly not used in daily drivers where day-in/day-out reliability is necessary. Instead, solid roller cams are intended for maximum performance/competition. Generally these cams are designed with very aggressive opening and closing rates. High seat pressures are necessary to keep the valves from bouncing when they come back to the seat. The high spring pressures require the use of high strength, one-piece valves. However, Crane does offer the SR-Series of Street Roller camshafts intended for daily usage.<br> |
| − | ##Seat | + | ##Seat pressure is determined by valve/retainer weight, engine RPM and life expectancy of components before replacement is required. <br> |
| − | ##Open | + | ###Milder roller cams require 165# on the seat as an absolute minimum. <br> |
| − | ###Street/ | + | ###180-200# is common for most modest performance applications. <br> |
| − | ###Circle track and moderate bracket racing 450-600 | + | ###220-250# is common for most serious sport categories and some circle track professional categories. <br> |
| − | ###Serious drag racing and limited distance circle track racing 600# and | + | ###Pro-Stock and Blown Alcohol/Fuel drag applications use as much as 340-500# on the seat.<br> |
| + | ##Open pressure need to be high enough to control the valvetrain as the lifter goes over the nose of the cam. Ideally, the minimum amount of open pressure to eliminate or minimize valvetrain separation is desired. Any excess open pressure only contributes to pushrod flex, which can aggravate valvetrain separation. For serious racing applications this can be determined only by experimentation and track testing. For general guidelines we offer the following:<br> | ||
| + | ###Street/strip performance with long cam/lifter life desirable, 350-450# open. | ||
| + | ###Circle track and moderate bracket racing 450-600# open. | ||
| + | ###Serious drag racing and limited distance circle track racing 600# and up. | ||
==Resources== | ==Resources== | ||
| + | *[[Media:Crane pdf.pdf|About Valve Springs]]: Crane valve spring catalog and specs | ||
;Crankshaft Coalition wiki articles | ;Crankshaft Coalition wiki articles | ||
*[[Valve train points to check]] | *[[Valve train points to check]] | ||
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