Rocker Geometry

Mark460 June 22nd 2011, 12:04 pm

I did some searching on this forum and others, and read about the midlift theory and other methods for checking pushrod length.
What I have a street strip, 460, DOVE heads, Comp XE274 (about .565 lift). Rockers are aluminum 1.73 ratio. With stock pushrods, blueing on valve tips, pattern showed contact pattern off center and outboard of valve tip(see pic).

Rocker Geometry Patten

With an adjustable pushrod about .050 shorter contact pattern centers more. Maybe I’m making this more complicated than it should be, but should I put a dial indicator on it so I can measure the sweep?
Pic, midlift with stock pushrod.
Rocker Geometry Stock-midlift

Should I just run this thing the way it is? Does anyone have any advice, comments, etc.
Thanks

rmcomprandy June 22nd 2011, 1:18 pm

When using a roller tip rocker arm, I would be more concerned with the geometry on the pushrod side of the rocker arm and getting the "pushrod tip to rocker arm cup" angularity closest to correct and forget about what the Valve tip pattern looks like; (as long as it is decent and that pattern is not near either edge of the valve tip).

Mark460 June 22nd 2011, 5:10 pm

What should I look for on the pushrod side? Here is the other side at half lift.
Rocker Geometry 050-pushrod

Lem Evans June 22nd 2011, 5:52 pm

I'm not much on theory but, I like a sweep that is near the center of the stem and the most narrow.

ROAD RAGE June 22nd 2011, 6:22 pm

just being a bit nosey, But what length stud do you have there?????????????

rmcomprandy June 22nd 2011, 7:57 pm

Mark460 wrote:What should I look for on the pushrod side? Here is the other side at half lift.

To be able to control the most load with the least amount of deflection, (a lot of times you don't really need to control the MOST load if your in an overkill situation anyway), the pushrod cup should be perpendicular to the pushrod from 2/3 to 3/4 lift. The pushrod to rocker arm interface carries a lot more load than the valve tip; (valve tip pressure TIMES the rocker ratio). AND, it's ALL friction as there is no roller on that side. Some compromise between the two sides is often required to get both in an acceptable condition with neither side being completely correct.
At relatively low spring pressures for a racing engine it really isn't much of a problem however, as the spring rates and the pressures grow, it can become one, fast.

c.evans June 22nd 2011, 11:14 pm

I agree with Randy, and I agree with Lem, based on what I see, I think a little shorter pushrod would put that pattern more towards the middle of the valve stem. I don't like how far outboard the roller is in that side view. I think the pushrod intersection looks great, and will still be acceptable with a little shorter pushrod.

Charlie

gtotomm June 23rd 2011, 12:35 am

What matters is mid lift at 90* The radial motion of your rocker arm is the most efficent. and you will have the least amount of sweep accross the stem tip. It does not matter if the pattern is off center as long as it doesnt get near the end. In a perfect world it should be centered, but offten this is not the case. In most cases a compromise is in order. The narrower the sweep the less scrubbing or wasted motion across the tip there is. study

Read "rocker arm geometry by Jim Miller"

rmcomprandy June 23rd 2011, 1:03 am

gtotomm wrote:What matters is mid lift at 90* The radial motion of your rocker arm is the most efficent. and you will have the least amount of sweep accross the stem tip. It does not matter if the pattern is off center as long as it doesnt get near the end. In a perfect world it should be centered, but offten this is not the case. In most cases a compromise is in order. The narrower the sweep the less scrubbing or wasted motion across the tip there is. Read "rocker arm geometry by Jim Miller"

There are many theories, (theories not fact), about what constitutes correct geometry. Least friction ... point of least deflection ... least "in & out" movement ... most geometrically efficient ... and then, that all changes again when the rocker arm is a scrub tip rocker and not a roller tip rocker.
No single one of those theories is right or wrong as all have their specific pluses and minuses.

Personally, I prefer the longevity; don't break; least amount of deflection theories. Especially when very high valve spring pressures are being used.

EDIT: "When testing, if the results differ from your theory ... BELIEVE the results and invent a new theory", Mike Urich

gtotomm June 23rd 2011, 1:34 am

Mike, When a roller tip sweeps across the top of a valve stem tip, if it is not at its most efficent motion,(mid lift at 90*) cam info is being wasted through the valve train any time the radial motion of the rocker arm is pushing across the tip. Mid lift geometry allows for the least wasted radial motion of the rocker arm. Im refering to a roller tip of coarse. If a roller tip rocker at mid lift is at 90*(trunnion center to roller tip center) it has the same amount of sweep from 0 to mid lift as it does from mid lift to full lift. Resulting in no wasted motion, period. All the information the cam is giving out is used and not wasted. This can actually be measured in degree's w/ a degree wheel. it may be minimal, but lost non the less. That is fact and not theroy. Bottom line: as close to center as possible w/ the narrowest contact patch. Slightly off center is ok.

rmcomprandy June 23rd 2011, 10:01 am

gtotomm wrote:Mike, When a roller tip sweeps across the top of a valve stem tip, if it is not at its most efficent motion,(mid lift at 90*) cam info is being wasted through the valve train any time the radial motion of the rocker arm is pushing across the tip. Mid lift geometry allows for the least wasted radial motion of the rocker arm. Im refering to a roller tip of coarse. If a roller tip rocker at mid lift is at 90*(trunnion center to roller tip center) it has the same amount of sweep from 0 to mid lift as it does from mid lift to full lift. Resulting in no wasted motion, period. All the information the cam is giving out is used and not wasted. This can actually be measured in degree's w/ a degree wheel. it may be minimal, but lost non the less. That is fact and not theroy. Bottom line: as close to center as possible w/ the narrowest contact patch. Slightly off center is ok.

I think you don't know WRITTEN English very well or simply just comprehend whatever you like, and nothing else, when reading it.
What it does geometrically is fact ... whether or not that is THE BEST SOLUTION is ... T H E O R Y.

A lot depends upon on how that PARTICULAR rocker arm is designed and made. When the roller at the valve tip is directly in the center of the valve tip and of least movement to have the least amount of wasted motion yet the pushrod keeps bending or breaking because the angularity on that side is so far out in left field, (correct camshaft information isn't being transmitted anyway) ... then THAT is NOT the best solution. What WORKS for a long time IS the BEST solution...! There are TWO sides to a rocker arm and they MUST work together and if they don't , whether or not absolutely correct camshaft information is transmitted is of little use, if it breaks..
Just as an example, some rocker & valve train companies want the roller to start at the inside and move across the valve to the very outside in order to obtain maximum valve lift and promote the roller to roll so as to alleviate pointed wear on the roller axle; JESEL is not a "fly by night" company and has been in business selling WORKING rocker systems for years. It is still a THEORY, (his theory), as to whether or not this is THE BEST SOLUTION.
Although you seem to have your head in the sand to any other rocker theories and blindly and totally accept what you believe ... LESS WASTED MOTION is your ONLY solution, (that is what you are preaching here), and it is STILL just someone's THEORY as to finding "the best solution".

gtotomm June 23rd 2011, 12:21 pm

Mike, Jim Miller patented this, I wasnt aware you could patened a theory? Who needs to get there head out of the sand now?

Scott Foxwell June 23rd 2011, 1:26 pm

Lem Evans wrote:I'm not much on theory but, I like a sweep that is near the center of the stem and the most narrow.

I agree, although you seldom get both. I look for the narrowest pattern which is going to be closest to the 90* @ half lift geometry method. IMO where the roller tip sits on the valve is secondary.

dfree383 June 23rd 2011, 1:31 pm

gtotomm wrote:Mike, Jim Miller patented this, I wasnt aware you could patened a theory? Who needs to get there head out of the sand now?

He Patented his Rocker arms that Met the theory...... and used the name.

Scott Foxwell June 23rd 2011, 1:34 pm

rmcomprandy wrote:
gtotomm wrote:Mike, When a roller tip sweeps across the top of a valve stem tip, if it is not at its most efficent motion,(mid lift at 90*) cam info is being wasted through the valve train any time the radial motion of the rocker arm is pushing across the tip. Mid lift geometry allows for the least wasted radial motion of the rocker arm. Im refering to a roller tip of coarse. If a roller tip rocker at mid lift is at 90*(trunnion center to roller tip center) it has the same amount of sweep from 0 to mid lift as it does from mid lift to full lift. Resulting in no wasted motion, period. All the information the cam is giving out is used and not wasted. This can actually be measured in degree's w/ a degree wheel. it may be minimal, but lost non the less. That is fact and not theroy. Bottom line: as close to center as possible w/ the narrowest contact patch. Slightly off center is ok.

I think you don't know written ENGLISH very well or simply just comprehend whatever you like, and nothing else, when reading it.
What it does geometrically is fact ... whether or not that is THE BEST SOLUTION is ... T H E O R Y.

A lot depends upon on how that PARTICULAR rocker arm is designed and made. When the roller at the valve tip is directly in the center of the valve tip and of least movement to have the least amount of wasted motion yet the pushrod keeps bending or breaking because the angularity on that side is so far out in left field, (correct camshaft information isn't being transmitted anyway) ... then THAT is NOT the best solution. What WORKS for a long time IS the BEST solution...! There are TWO sides to a rocker arm and they MUST work together and if they don't , whether or not absolutely correct camshaft information is transmitted is of little use, if it breaks..
Just as an example, some rocker & valve train companies want the roller to start at the inside and move across the valve to the very outside in order to obtain maximum valve lift and promote the roller to roll so as to alleviate pointed wear on the roller axle; JESEL is not a "fly by night" company and has been in business selling WORKING rocker systems for years. It is still a THEORY, (his theory), as to whether or not this is THE BEST SOLUTION.
Although you seem to have your head in the sand to any other rocker theories and blindly and totally accept what you believe ... LESS WASTED MOTION is your ONLY solution, (that is what you are preaching here), and it is STILL just someone's THEORY as to finding "the best solution".

Wow...still using that golden personality of yours to make your point, eh Randy? Why don't you try and communicate sometime without the insults and attitude...there may be some truth to what you say (I say some) but the point really gets lost when you're just being an ass.
JMO

Scott Foxwell June 23rd 2011, 1:44 pm

To be able to control the most load with the least amount of deflection, (a lot of times you don't really need to control the MOST load if your in an overkill situation anyway), the pushrod cup should be perpendicular to the pushrod from 2/3 to 3/4 lift. The pushrod to rocker arm interface carries a lot more load than the valve tip; (valve tip pressure TIMES the rocker ratio). AND, it's ALL friction as there is no roller on that side. Some compromise between the two sides is often required to get both in an acceptable condition with neither side being completely correct.
At relatively low spring pressures for a racing engine it really isn't much of a problem however, as the spring rates and the pressures grow, it can become one, fast.

The most load a pushrod, lifter and rocker arm will ever see is at the initial movement off the base circle and accelrating up the ramp, not at max lift. Just something to think about. At max lift, the lifter can see zero load as it goes over the nose (called valve float). In fact, it should see zero load, and still maintain contact to be ideal.

rmcomprandy June 23rd 2011, 3:33 pm

Scott Foxwell wrote:
rmcomprandy wrote:
gtotomm wrote:Mike, When a roller tip sweeps across the top of a valve stem tip, if it is not at its most efficent motion,(mid lift at 90*) cam info is being wasted through the valve train any time the radial motion of the rocker arm is pushing across the tip. Mid lift geometry allows for the least wasted radial motion of the rocker arm. Im refering to a roller tip of coarse. If a roller tip rocker at mid lift is at 90*(trunnion center to roller tip center) it has the same amount of sweep from 0 to mid lift as it does from mid lift to full lift. Resulting in no wasted motion, period. All the information the cam is giving out is used and not wasted. This can actually be measured in degree's w/ a degree wheel. it may be minimal, but lost non the less. That is fact and not theroy. Bottom line: as close to center as possible w/ the narrowest contact patch. Slightly off center is ok.

I think you don't know written ENGLISH very well or simply just comprehend whatever you like, and nothing else, when reading it.
What it does geometrically is fact ... whether or not that is THE BEST SOLUTION is ... T H E O R Y.

A lot depends upon on how that PARTICULAR rocker arm is designed and made. When the roller at the valve tip is directly in the center of the valve tip and of least movement to have the least amount of wasted motion yet the pushrod keeps bending or breaking because the angularity on that side is so far out in left field, (correct camshaft information isn't being transmitted anyway) ... then THAT is NOT the best solution. What WORKS for a long time IS the BEST solution...! There are TWO sides to a rocker arm and they MUST work together and if they don't , whether or not absolutely correct camshaft information is transmitted is of little use, if it breaks..
Just as an example, some rocker & valve train companies want the roller to start at the inside and move across the valve to the very outside in order to obtain maximum valve lift and promote the roller to roll so as to alleviate pointed wear on the roller axle; JESEL is not a "fly by night" company and has been in business selling WORKING rocker systems for years. It is still a THEORY, (his theory), as to whether or not this is THE BEST SOLUTION.
Although you seem to have your head in the sand to any other rocker theories and blindly and totally accept what you believe ... LESS WASTED MOTION is your ONLY solution, (that is what you are preaching here), and it is STILL just someone's THEORY as to finding "the best solution".

Wow...still using that golden personality of yours to make your point, eh Randy? Why don't you try and communicate sometime without the insults and attitude...there may be some truth to what you say (I say some) but the point really gets lost when you're just being an ass.
JMO

You are certainly entitled to have your own opinion about what I say however, unless my eyes are deceiving me ... you are the one here directly calling people names, lol.
If you're paying any attention to the entire thread ... I only show "the attitude" when it gets shown to me first.

I was only pointing out obvious truth of selective comprehension right to the forefront without any BS to go along with it. I guess some people NEED it sugar coated with a lot of niceties thrown in.
Now ... do you have anything of value to say here??? That ... actually might be worth reading.

gtotomm June 23rd 2011, 3:41 pm

I agree w/ JMO

BigBlockRanger June 23rd 2011, 3:57 pm

Who the hell is Mike?

Lem Evans June 23rd 2011, 4:13 pm

Scott Foxwell wrote:
Lem Evans wrote:I'm not much on theory but, I like a sweep that is near the center of the stem and the most narrow.
I agree, although you seldom get both. I look for the narrowest pattern which is going to be closest to the 90* @ half lift geometry method. IMO where the roller tip sits on the valve is secondary.

Getting both has not been that big of a deal on the TFS A460 heads........using a Crower S.S. rocker and a standard [non-bastard] lenght valve.

gtotomm June 23rd 2011, 5:14 pm

Lem, its nice to see someone else understands mid lift geo. Rolling Eyes

BigBlockRanger June 23rd 2011, 5:28 pm

Useful link.

https://www.429-460.com/f8-introduction

rmcomprandy June 23rd 2011, 5:31 pm

gtotomm wrote:Lem, its nice to see someone else understands mid lift geo.

Understanding it, is not the issue as I completely understand the "Mid Lift" principals of less lost motion. I don't however, believe that it is the "be all, end all" way to curing ALL the different idiosyncrasies of valve train geometry in every application with a rocker arm known to exist. Especially when the design geometry of the particular rocker arm being used won't get to those parameters on both sides of the fulcrum no matter what you do.

Things would be great if it were all that simple; unfortunately, it isn't.

Scott Foxwell June 23rd 2011, 5:35 pm

Lem Evans wrote:
Scott Foxwell wrote:
Lem Evans wrote:I'm not much on theory but, I like a sweep that is near the center of the stem and the most narrow.
I agree, although you seldom get both. I look for the narrowest pattern which is going to be closest to the 90* @ half lift geometry method. IMO where the roller tip sits on the valve is secondary.

Getting both has not been that big of a deal on the TFS A460 heads........using a Crower S.S. rocker and a standard [non-bastard] lenght valve.

Someone did their homework, but not a surprise with Crower. It's frustrating to have to go through three or four different sets (brands) of rockers...all supposedly for the same application...to find one that works correctly. I've found that for BB Chev's (pardon the reference..lol) the Crane Gold is about the only one, so far, that "works". I know Crower offers rockers that are set back to help correct the "tall valve, off-center roller" syndrome, but as long as the roller is not much further than the outside third of the valve (or so) I don't worry too much about it...long as the geometry is right. Canfield even stated in their literature that their heads were designed around a Cranae Gold rocker. It's also why I suggest Scorpion race series these days...they supposedly took up the Crane design. They look very similar and the last set I did worked out well.

Scott Foxwell June 23rd 2011, 5:38 pm

rmcomprandy wrote:
Scott Foxwell wrote:
rmcomprandy wrote:
gtotomm wrote:Mike, When a roller tip sweeps across the top of a valve stem tip, if it is not at its most efficent motion,(mid lift at 90*) cam info is being wasted through the valve train any time the radial motion of the rocker arm is pushing across the tip. Mid lift geometry allows for the least wasted radial motion of the rocker arm. Im refering to a roller tip of coarse. If a roller tip rocker at mid lift is at 90*(trunnion center to roller tip center) it has the same amount of sweep from 0 to mid lift as it does from mid lift to full lift. Resulting in no wasted motion, period. All the information the cam is giving out is used and not wasted. This can actually be measured in degree's w/ a degree wheel. it may be minimal, but lost non the less. That is fact and not theroy. Bottom line: as close to center as possible w/ the narrowest contact patch. Slightly off center is ok.

I think you don't know written ENGLISH very well or simply just comprehend whatever you like, and nothing else, when reading it.
What it does geometrically is fact ... whether or not that is THE BEST SOLUTION is ... T H E O R Y.

A lot depends upon on how that PARTICULAR rocker arm is designed and made. When the roller at the valve tip is directly in the center of the valve tip and of least movement to have the least amount of wasted motion yet the pushrod keeps bending or breaking because the angularity on that side is so far out in left field, (correct camshaft information isn't being transmitted anyway) ... then THAT is NOT the best solution. What WORKS for a long time IS the BEST solution...! There are TWO sides to a rocker arm and they MUST work together and if they don't , whether or not absolutely correct camshaft information is transmitted is of little use, if it breaks..
Just as an example, some rocker & valve train companies want the roller to start at the inside and move across the valve to the very outside in order to obtain maximum valve lift and promote the roller to roll so as to alleviate pointed wear on the roller axle; JESEL is not a "fly by night" company and has been in business selling WORKING rocker systems for years. It is still a THEORY, (his theory), as to whether or not this is THE BEST SOLUTION.
Although you seem to have your head in the sand to any other rocker theories and blindly and totally accept what you believe ... LESS WASTED MOTION is your ONLY solution, (that is what you are preaching here), and it is STILL just someone's THEORY as to finding "the best solution".

Wow...still using that golden personality of yours to make your point, eh Randy? Why don't you try and communicate sometime without the insults and attitude...there may be some truth to what you say (I say some) but the point really gets lost when you're just being an ass.
JMO

You are certainly entitled to have your own opinion about what I say however, unless my eyes are deceiving me ... you are the one here directly calling people names, lol.
If you're paying any attention to the entire thread ... I only show "the attitude" when it gets shown to me first.

I was only pointing out obvious truth of selective comprehension right to the forefront without any BS to go along with it. I guess some people NEED it sugar coated with a lot of niceties thrown in.
Now ... do you have anything of value to say here??? That ... actually might be worth reading.

Telling someone they have their head in the sand or don't comprehend the english language, just becuase you disagree with them, is being an ass. That's how you are. It's not name calling, it's an accurate description. You treated me the same way on 460.com and right here, right now, I'll say I'm not going to put up with it for a New York second. It's immature, and totally uncalled for. If that makes me the bad guy, so be it.
As far as what I have to offer, I've alredy corrected you once. I'll be glad to do it again.

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