If you can believe the below, I borrowed from another tech site, your valve train geometry being off has more effect on side loading of valve stem than cam lift.
Looks like reguardless of lift, valve train geometry being off is biggest factor in side loading and not cam lift. But maybe the higher the lift the more side load pressure applied so it becomes more important to run RRs if valvetrain geometry isn't corrected.
"A well designed and lightweight roller rocker can be of benefit in a high performance engine. With that said, and to answer your question, when is a roller rocker *necessary*? Well, the true answer is that there is no lift value, ramp style, or lobe shape that absolutely requires a roller rocker. If the valve geometry is set correctly, a non-roller rocker can be used for all but the highest of lifts and lobes that will normally be found in street application cams. Rollers are often used to reduce side loads with medium aggressive street cams simply because the builder is too lazy or doesn't know how to check and correct the valve geometry, in those cases the roller can help, but if the geometry is way off there will still be excessive side loads applied to the valve stems and guides.
The illustrations below show the basic contact patch that should be looked for when checking valve geometry. Some engine builders will look for a pattern that gets no closer than 0.050" to 0.060" to the edge of the stem, others, like myself, look for a pattern that is centered and has a *maximum width* of 0.050" to 0.060". A well centered and minimal contact patch will give the best valve train wear and performance. On a higher lift cam (for HD's and street use I consider this to be lifts exceeding 0.580") the combination of a roller rocker *and* correct geometry will usually result in maximum valve train longevity. How much longer than a non-roller setup? It's still a crap shoot, IMO. I've seen non-roller setups that have less guide wear than a roller setup with the same cam and vice-versa for a given mileage. In many cases I use them simply because the owner either demands them or is expecting them as part of a high dollar, high performance build. On a pure racing, no holds barred, maximum effort engine a lightweight, *stiff*, roller setup would be my choice for any pushrod motor. On the street? I tend not to go with super high lift, aggressive lobe profile cams so rollers are not usually necessary. I do have them in my own personal motor, but I could just as well have done without them. The choice is yours, I can build a motor with or without roller rockers that will likely last you a long time. If having roller rockers gives you a warm, fuzzy feeling, then by all means go for it. The difference between the two setups with respect to top end overhaul frequency will be negligable as long as the valve geometry is set correctly."
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Play nice now.
Looks like reguardless of lift, valve train geometry being off is biggest factor in side loading and not cam lift. But maybe the higher the lift the more side load pressure applied so it becomes more important to run RRs if valvetrain geometry isn't corrected.
"A well designed and lightweight roller rocker can be of benefit in a high performance engine. With that said, and to answer your question, when is a roller rocker *necessary*? Well, the true answer is that there is no lift value, ramp style, or lobe shape that absolutely requires a roller rocker. If the valve geometry is set correctly, a non-roller rocker can be used for all but the highest of lifts and lobes that will normally be found in street application cams. Rollers are often used to reduce side loads with medium aggressive street cams simply because the builder is too lazy or doesn't know how to check and correct the valve geometry, in those cases the roller can help, but if the geometry is way off there will still be excessive side loads applied to the valve stems and guides.
The illustrations below show the basic contact patch that should be looked for when checking valve geometry. Some engine builders will look for a pattern that gets no closer than 0.050" to 0.060" to the edge of the stem, others, like myself, look for a pattern that is centered and has a *maximum width* of 0.050" to 0.060". A well centered and minimal contact patch will give the best valve train wear and performance. On a higher lift cam (for HD's and street use I consider this to be lifts exceeding 0.580") the combination of a roller rocker *and* correct geometry will usually result in maximum valve train longevity. How much longer than a non-roller setup? It's still a crap shoot, IMO. I've seen non-roller setups that have less guide wear than a roller setup with the same cam and vice-versa for a given mileage. In many cases I use them simply because the owner either demands them or is expecting them as part of a high dollar, high performance build. On a pure racing, no holds barred, maximum effort engine a lightweight, *stiff*, roller setup would be my choice for any pushrod motor. On the street? I tend not to go with super high lift, aggressive lobe profile cams so rollers are not usually necessary. I do have them in my own personal motor, but I could just as well have done without them. The choice is yours, I can build a motor with or without roller rockers that will likely last you a long time. If having roller rockers gives you a warm, fuzzy feeling, then by all means go for it. The difference between the two setups with respect to top end overhaul frequency will be negligable as long as the valve geometry is set correctly."
Play nice now.
