Valve train geometry

Discussion in 'Small Block Mopar Engine' started by N1ce2k1llu, May 3, 2018.

  1. N1ce2k1llu

    N1ce2k1llu Active Member

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    My roller rockers don't center up on the valve stem. I can't shim them up because it puts it closer to the edge and can't lower them because there mounted on pedestal's. What option do I have? AND besides wearing out my guides quicker, how bad would it be to run it like this?
    1971/ 318LA, street cruiser.

    20180427_214741-1.jpg

    20180502_201514.jpg
     
  2. yellow rose

    yellow rose Doctor of Thinkology.

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    B3racingengines.com

    Read his tech articles and then call him. He has the fix and it needs to be fixed.
     
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    • RustyRatRod

      RustyRatRod Just another dumbass. FABO Gold Member Technical Editor

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      Naw don't tell him that. All I read was "I caint do this and I caint do that".
       
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      • fishy68

        fishy68 Tyr Fryr's Inc. FABO Gold Member

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        Since they are roller rockers they won't produce as much side pressure on the valve stem so it won't wear on the guides nearly as bad as a stock rocker. If I'm not mistaken someone has some offset shims available. Might be the fellow YR mentioned
         
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        • Greg Spooner

          Greg Spooner Active Member

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          It will be difficult to achieve on centre contact without going higher and offsetting the shaft towards the intake, your contact area looks similar to what I finally achieved on my heads.
          The consensus seems to be that a roller tip won’t be as prone to side loading the valve and importantly, minimising the width of the contact area is as important as anything and yours looks pretty narrow to me.
           
        • Abodybomber

          Abodybomber Breaking street machines , since 1983.....:)

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          Try lash caps ,....
           
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          • RustyRatRod

            RustyRatRod Just another dumbass. FABO Gold Member Technical Editor

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            Oh nasty.
             
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            • Abodybomber

              Abodybomber Breaking street machines , since 1983.....:)

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              Yeah ,I know...
               
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              • nm9stheham

                nm9stheham Well-Known Member

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                The roller tips put no appreciable side on the stems; that is the point of using them. Centering the pattern does not change the side loading at all. So don't worry over that.

                And not being centered is not of concern as long as they are not too far off center. The thinking that being perfectly centered is the best geometry is dead wrong. What you care about is the scrub pattern being narrow. Measure the width of the scrub pattern; even with the best possible setup, you won't get it much narrower than .035" with around .500" lift.
                 
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                • yellow rose

                  yellow rose Doctor of Thinkology.

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                  The shafts need to go up and away from the valves. It's that simple. Fix it.

                  I gave you the contact information to the man who can fix up for a reasonable price and then your valve train will function like it should and not be compromised.

                  Will what you have work? Yes. Is it right? Not by a long shot. Fix it correctly now, or deal with it later. I'm a fix it now type of guy.
                   
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                  • Wyrmrider

                    Wyrmrider Well-Known Member

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                    If heads are milled do I need shorter pushrods?

                    and op you are close enough IF you have gone through the mid lift drill
                    so do that and report your procedure
                    lash caps can help with stock rockers
                    they may make roller rockers worse
                    YMMV
                     
                  • mullinax95

                    mullinax95 Well-Known Member

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                    Before and after B3Racing geo kit... do it!
                    Valve 1.JPG
                    Valve2.jpg
                     
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                    • tanis4457

                      tanis4457 Well-Known Member

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                      My B3 kit resulted in a swepth width of about .0042 through the entire arc and looked close to the second photo, definitely worth the money.
                       
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                      • Wyrmrider

                        Wyrmrider Well-Known Member

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                        YEP and lots of reasons why
                        BTW do not use the Lunati Method without thiking through what they are saying
                        How to Verify Valvetrain Geometry - Lunati Power
                        that's for ball stud rockers where you can raise and lower the fulcrum easily "The pattern should be centered on the valve tip" In a perfect world- get the spacers
                        , and as narrow as possible. got that right
                        If it is not, experiment with varying the pushrod length to yield the best pattern. uh what is the best pattern?
                        if a shaft rocker go as narrow as possible and ignore where the pattern is on the valve tip- unless it's way near the edge

                        Comp's method was worse last time I looked
                         
                      • B3RE

                        B3RE B³ Racing Engines

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                        If you aren't moving the fulcrum, you aren't correcting the geometry.

                        What determines how centered the sweep pattern is on the valve tip.

                        Exactly how does pushrod length affect the sweep pattern?

                        What determines how narrow a pattern is possible?

                        The Comp method is ignorance at its finest.
                         
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                        • Wyrmrider

                          Wyrmrider Well-Known Member

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                          Agree but getting the pushrod length right with the narrowest pattern does most of it with a stock or Iron rocker
                          there is moving the shaft back and forth
                          So if you are not moving the fulcrum you are correcting but not getting it perfect- and not really correcting with roller tip rockers- those pictures are GOLDEN
                          or up and down (necessary when changing to roller tip rockers as the tip curve point is raised by the radius of the roller over stock or Iron
                          How centered the sweep pattern is (with the sweep as narrow as possible) is a mechanical problem not a pushrod adjustment problem
                          with an Iron or stock rocker you have to move the shaft back and forth- but since you are usually dealing with a longer valve and/or more lift you may have to raise it also

                          What determines how narrow ? Tangent of line through fulcrum and pad or center of lifter and the valve stem at half lift
                          Tip height at half lift does not change without a lash cap so result is you have to move the shaft no fix by just changing pushrod length
                          What determines ho narrow a pattern is possible?
                          Length of the arm for example a back set fulcrum Crower has a longer arm can have a narrower pattern than a stock length arm (Chevy)
                          The backset fulcrum also allows the use of a closer cup to fulcrum distance for more ratio or bigger pushrods as teh cup moves away from the fulcrum too

                          Crane also had funny Ideas on rocker geometry- usually Harvey was with it but not his early rocker arms- or early harland sharp
                          ever see the ones where the arm was on top of the shaft? really funny motion
                          Racer Brown was the first I know of to really understand
                          Mike Jones Understands
                          I got another one for U
                          if you want smooth valve action what do you do to not only modify the lobe for the change in rocker ratio as lift goes to tangent and away, but on a Early Hemi or LA to account for the lifter/ pushrod angle
                          (same problem with porkypine angled rockers like BBC)
                          One thing to check on solid cams/ adjustable rockers is IS the adjuster in line with the pushrod at half lift
                          cheers
                           
                          Last edited: May 4, 2018
                        • B3RE

                          B3RE B³ Racing Engines

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                          I have to disagree. Even with a stock non roller rocker, the pushrod length will not change the geometry at the valve. It will affect how high or low the adjuster is in the rocker, which will have an effect on ratio, therefore increasing or decreasing net lift, which will increase or decrease the width of the pattern. The geometry has not been made better by doing that.

                          Without getting too technical, suffice to say that what dictates the location of the pattern is the rockers fulcrum length. So, having to move the rocker laterally in relation to the valve stem would mean the rocker is either too long, or too short for the cylinder head design.

                          Yes, the fulcrum length will affect the width slightly, but the prominent cause is the amount of net valve lift. To just say narrowest sweep possible without knowing what it should be, is flying blind in my opinion. If someone was to play with the pushrod length and reduce the ratio, it would narrow the pattern, but they wouldn't be correcting the geometry. They would just be introducing more inefficiency into the valvetrain.

                          I approach every engine with pushrod angularity the exact same way. With trigonometry. What about an LA with 59 degree tappet and a cylinder head that has a .700" intake rocker offset. Holy compound angles Batman!

                          The first thing I compensate when going to a higher ratio rocker on a mechanical tappet cam is the lash. Then, if the lobe is aggressive, I'll be on the phone with the cam grinder for his input. I rely on others for what they are good at, just like they rely on me for what I am good at.

                          There are an awful lot of rocker arms out there that have the adjuster in line with the pushrod, or reasonably close, at half lift, yet they are still inefficient. My custom rockers take care of this problem, but those design parameters are proprietary. There's a little more to it than just a straight line.
                           
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                          • Wyrmrider

                            Wyrmrider Well-Known Member

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                            comp says
                            What is correct valve train geometry? When the rocker arm roller tip rolls from the intake side of the valve tip, across the center of the tip (at approximately mid-lift), to the exhaust side of the valve tip (at full lift) and back. See Diagram A.
                            now how is that helpful?

                            On geometry say with a short pushrod moving the ball from angle down to tangent at full lift or a long pushrod moving from tangent to rocker tilted way down at full lift does change the geometry. There are camgrinders that recommend tangent at 1/3 lift (less ratio near full lift- sometimes used as a crutch for valve float) to others 2/3 lift (gives more lift but higher ratio when springs are more compressed)
                            But I can see it the way U do what a great product
                            WE used to move/ shim the stands on early Big blocks with the replaceable stands

                            what dictates the location of the pattern is the rockers fulcrum length---or the location of the shaft/ stud- relocate studs all the time

                            . "If someone was to play with the pushrod length and reduce the ratio, it would narrow the pattern, but they wouldn't be correcting the geometry. They would just be introducing more inefficiency into the valvetrain". ?? Anytime you make the pushrod too short or too long you reduce the ration and widen the pattern at the same time- correct?

                            Holy Compound Batman- LMFAO
                            yet they are still inefficient. The balls /cups are in the wrong spots
                            DO you go to larger adjusters (thread) and larger cups/ balls?
                            Those pictures show why your spacers are an essential start
                            cheers
                            learn something new every day
                             
                          • B3RE

                            B3RE B³ Racing Engines

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                            Comp? Who is Com....oh, you mean the cam company who has a spintron, but still applies stock rocker geometry to a roller rocker. Yeah, Not at all helpful.

                            I never understood why a cam grinder, or anyone else, would recommend altering the information ground into the cam lobe by screwing with the rocker efficiency. What ever do the Formula 1 teams do with those overhead cams and no rocker arms to jack around. Hmm, maybe they just have a great cam lobe and properly matched components in the valvetrain. That makes a lot more sense to me.

                            My point with the rocker fulcrum length is that we have a cylinder head design and a rocker arm that is supposedly designed for that head. Why is it necessary to move the stands or studs so the rocker fits properly. This is something else I addressed with my custom rockers.

                            More lift will give more sweep, so reducing the ratio with pushrod length will reduce net lift and result in less sweep.

                            The only changes I make to off the shelf rockers, is to change them from ball to cup style adjusters. That helps the pushod geometry slightly, and makes pushrod selection easier. It does not make it perfect. My custom rockers exist simply because there aren't any rockers off the shelf that have the correct adjuster geometry. You mention my spacers being a good start. Well, they are the best that can be done to help, not fix, the rockers that are available. If you want it all to be perfect, my custom rockers, in conjunction with the shaft spacers, is the only game in town.

                            I believe I mentioned it before, but my kits don't correct the rockers. They correct the heads so the stand heights are correct for proper valve side geometry. If you want the pushrod side to be correct, the rocker has to be designed with the correct fulcrum point in mind. None of the shelf rockers do that. Not sure if I mentioned it, but my custom rockers do.:D

                            Thanks for the dialog. I like people who know how to think. I'm sure we'll be able to learn a few things from each other in the future.
                             
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                            • rumblefish360

                              rumblefish360 so close yet so far away

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                              @B3RE You forgot your converter act info.
                               
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                              • B3RE

                                B3RE B³ Racing Engines

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                                I'm sorry rumble, but I'm not following. "Converter act info" is drawing a blank.
                                 
                              • moper

                                moper FABO Gold Member FABO Gold Member

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                                I think he means "contact info".... Spell checker at work :)
                                 
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                                • rumblefish360

                                  rumblefish360 so close yet so far away

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                                  Oh good gravy! I’m sorry B3RE, that was a quick post and run. Where are you located?

                                  Moper, thank ya buddy!

                                  Yes!

                                  “Contact info” is what it was to read!
                                  LMFAO!
                                  :rofl:
                                   
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                                  • B3RE

                                    B3RE B³ Racing Engines

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                                    Oh, lol. My brain must be on vacation. Spell check kills me, too.

                                    I can be contacted by PM, or by the phone or email at the Web link Yellow Rose provided.
                                     
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                                    • Wyrmrider

                                      Wyrmrider Well-Known Member

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                                      yup
                                      not a math whiz but know those who are or just insightful / mostly were unfortunately
                                      Racer Brown, Dick Jones Barney Navarro
                                      I used to try and set up rockers with a straight line through the pushrod ball, fulcrum, rocker tip/ stem or center of the roller at half lift but did play with others
                                      If pattern was off side to side too much I'd move the shaft/ stud never tried (well once) centering the pattern
                                      We had one of the first Mopar Max wedge 3 speed cars- then 4 speed - then torque flyte- (driver was not Ronnie Sox) had it tuned at Don Nicholson's Blair's Speed shop dyno- he always left it with too much advance but helped the low and mid range. Isky ground us a special .904 lifter cam which I see is no longer in the catalog- VERY consistent
                                      we used it to dial in chassis for years Those early Max Wedge Heads had aluminum replaceable stands- later we milled the cast stands off and used the earlier ones
                                      also made spacers, drilled the shafts off center, used larger hold down bolts in holes drilled off center, etc
                                      get it right and valve train was much more stabil, = wish we had todays springs back then
                                       
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