Rocker arm recommendations?

Big Block A body Tech

  1. yellow rose

    yellow rose Overnight Sensation FABO Gold Member

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    The reason long pushrods increase the rocker ratio is because the angle at which the adjuster goes through the rocker arm.

    The shorter the pushrod, the longer the adjuster. The longer the adjuster, the further away from the pivot the adjuster is. That reduces the rocker ratio.

    With Chrysler oiling the adjuster needs to be 9/32 out, plus .050 minus zero. Ok, it may be plus zero, minus .050 but I don’t have the book here to refresh my memory.

    Most guys run the pushrods way too short. If it’s a cup style adjuster I run them as far up the rocker as I can and still get oil to the adjuster.
     
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    • B3RE

      B3RE B³ Racing Engines

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      Uh oh! Now he gunning for Jim! The hole just keeps getting deeper.
       
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      • B3RE

        B3RE B³ Racing Engines

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        And that assumes the rocker is actually designed properly. Pretty much all of them have the angle wrong and the adjuster way too low to get a long enough pushrod in there. I don't know how you can have a "longer than optimum" pushrod in that situation.
         
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        • fishmens67

          fishmens67 Well-Known Member

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          He don't want to mess with Jim. Let Jim enjoy retirement and pop in with his own projects.
          We get good info from his own builds.
          He's not leaving out the top secret stuff like he did with his commercial builds.
           
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          • IQ52

            IQ52 Well-Known Member

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            I personally have no experience with "longer than optimum pushrods" Is that like giving 110% or rather 10% more than you actually have?

            Anyway......

            With a rocker shaft system........

            Just by holding an adjustable rocker arm in your hands and moving the adjuster in and out, you can answer your own question.

            For an example.....

            I have here at this moment a Brand-X aluminum roller rocker arm.

            To display the pushrod effect on this rocker I extended the adjusting screw out 9 turns (to simulate a short pushrod) and measured the distance from the center of the adjuster ball to the rocker shaft by simply using a dial caliper. Then I moved the adjuster screw in until there were no threads showing (to simulate a longer pushrod) and then again measured from the center of the adjuster ball to the rocker shaft.

            In this example the ball moved approximately .020"-.025" closer to the rocker shaft when there were no threads showing (like the longer pushrod). Moving the adjuster ball closer to the fulcrum increases the rocker ratio and thereby increases the lift.
             
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            • aaronk785

              aaronk785 Well-Known Member

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              You guys are way to smart for me.
               
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              • Bewy

                Bewy Well-Known Member

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                IQ,
                Totally agree with your test. But just as the ratio changes on the p'rod side, it also changes on the valve side because the rocker is in a new starting position when you change the prod length. The ratio is not constant on the prod side...or the valve side.
                Smokey said it, & I quoted him because he was & is correct.
                This [ the ratio change on both the prod & valve side ] was comprehensively demonstrated with the drawings accompanying the Crane quick lift rockers. Article appeared in Circle Track magazine Jan 06.
                With a rocker arm, both the prod cup [ or ball ], and the roller tip on the valve side swing through arcs. The drawing shows A & A1 for the prod side, B & B1 for the valve side. A & B are the at rest, or starting positions; A1 & B1 are the actual positions as the rocker starts lifting the valve. A1 & B1 are longer than A & B.....& that is because the ratio changes on each side.
                The text describes it:
                "The relative change of A1 to A is much greater than B1 to B; therefore the rocker ratio decreases as the valve opens. This is due to the low position of the pushrod seat with respect to the low position of the prod seat with respect to the centre of rocker body rotation."

                The amount of ratio change & where it occurs in the lift cycle is going to depend on the individual rocker design & geometry. This is what D. Vizard was demonstrating in his rocker tests; he tested 24 types of rocker.
                 
              • Bighead440

                Bighead440 Well-Known Member

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                Loving this "discussion." Back in the late '80s, working with a friend on a budget build of a 360 in his '71 Duster Twister (wish I had the car in the same condition today!), out of necessity we modified (ground) some 273 rocker bodies on the ball side of the adjuster boss to allow the use of the 273 solid pushrods with hydraulic lifters. This did increase the rocker ratio a little bit (as Jim said, moving the ball closer to the shaft centerline), as we measured the lift at the valve (with a shimmed-solid hydraulic lifter) to be close to .480" when the cam (an ancient Crane Blazer or Fireball grind) was advertized just under .450". I was skeptical about the oiling and longevity of the modifications, but it worked perfect for my friend for many street miles and missed 4speed shifts and overrevs. A full 15yrs later, I was at a dragstrip a few hours from home helping another friend at the track with his Super Street 440 Duster and a guy there that night asked me if I wanted a "Muncie 4speed Duster drag car?" Went and looked at it, and yes, it was my friends old Twister, so I bought it! He told me they drag raced the car for years with a 5.12 gear, and overreved it many times and bent some pushrods. Being Chevy guys, they went to Super Shops and ordered pushrods for a hydraulic/adjustable rocker LA motor. TOO SHORT, LOL!! So the guy said they had to buy "custom" Erson pushrods, but they are really shelf mechanical pushrods, hope they didn't pay a premium. The rockers, shafts and adjusters looked so good, I reused them in a 367 I later built with some maxxed out J heads and turned 7000rpm regularly with a .508" hydraulic cam, and the measured lift at the valve was right at .530".
                 
              • IQ52

                IQ52 Well-Known Member

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                Up to this point in time my discussion has centered on shaft mounted rockers. And on shaft mounted rockers the roller contact point on the valve tip will not change.....I love saying this.......even if you remove the pushrod and throw it across the room.

                To change the roller contact point by using a different pushrod one would be using a stud mounted rocker arm.

                I am currently studying the Jan, 2007 article on the Crane shaft mounted quick lift rockers.
                 
              • AndyF

                AndyF Well-Known Member

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                You can get more lift with a shaft mounted rocker arm by changing the pushrod length. I used to use this trick on my dyno engines but it comes with a price. For extra salt in the wounds, the extra lift often doesn't generate any more power.
                 
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                • B3RE

                  B3RE B³ Racing Engines

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                  I doubt that. The most important thing I have ever learned is to think, not let someone else think for me. If you can think and apply logic, a whole new world opens up to you.
                   
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                  • B3RE

                    B3RE B³ Racing Engines

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                    The Crane quick lift rockers achieved quicker lift off the seat by a higher fulcrum, and/or an "unusual" pushrod seat location. They also beat the crap out of the seats, because they closed just as fast.
                     
                  • B3RE

                    B3RE B³ Racing Engines

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                    If you can gain lift by putting a longer pushrod in the motor, then shouldn't this give you a clue that something isn't kosher with the rocker design? It should, because a properly designed rocker should lose lift if a longer, or shorter than optimum length, pushrod is used. Like I said earlier, a lot of funky nonsense can be done with a rocker, but the cam lobe is the "brain" information that tells the valve what to do. You aren't likely to make more power with more lift if the cam lobe information isn't being transmitted accurately.
                     
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                    • B3RE

                      B3RE B³ Racing Engines

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                      You can test 100 Billion rockers, and if they are improperly designed, you will get skewed results. Remember GIGO? Garbage in, garbage out.

                      Look at the video link Yellow Rose posted in the Racers Forum. Reid Rockers also confirms what I have been saying. Of course he probably doesn't carry enough credibility compared to the deities of Yunick and Vizard. He only has NHRA Fuel and Alcohol championships, but probably not as many as Smokey or DV.

                      Rocker arm webinar | For A Bodies Only Mopar Forum

                      It appears that you read a lot. That's a good thing, but you also have to be able to think critically. There is a lot of incorrect information in print, and a lot of experiments and compromises related to this subject. If you want to make an argument, use your own logic and make your case. I am always willing to learn something new, but quoting years old printed information doesn't show any real thought on your part, and doesn't tell me anything I haven't already heard and analyzed. It seems you are more interested in "being" right, than "knowing" right.
                       
                      Last edited: May 9, 2021
                    • Bewy

                      Bewy Well-Known Member

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                      B3,
                      Might come as shock to you but I do...&...did.....'think' this out for myself. The reason I quote other well known folks in this industry is that their opinions & knowledge will carry more weight in an argument than a nobody like me. Strength in numbers as they say...

                      There may be a 'perfect' rocker, I am not sure there is because of all the factors involved. But what makes it perfect? Generates max valve lift? Leaves the narrowest mark on the valve tip? Produces the least amount of valve guide wear? Gives the valve the gentlest seating action? ???? Is it a compromise?

                      And so far, the only 'knowing right' that I have claimed is that the there is a p'rod side ratio & a valve side ratio & they change throughout the lift cycle. I have made no other claims other than that. Nothing to do with 'being right' but everything to do with how something works. The fact that someone worked out a loooong time ago how it 'works' doesn't make it wrong or out of date, it just means they understood that far back.....
                       
                    • IQ52

                      IQ52 Well-Known Member

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                      Yep, I feel like the cat chasing the laser beam on the wall again. All this information has been covered.
                       
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                      • B3RE

                        B3RE B³ Racing Engines

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                        Not sure strength in numbers is a good thing if your talking about lemmings. It's like science being settled by consensus and not accurate data.

                        A perfect rocker is something that can't be improved upon. Technology will always find improvements, but math is math. No one ever came up with a math equation that changed the outcome of natural law. They just discovered a formula to explain the outcome. It just shows how insignificant we are in the universe.

                        With todays technology, a "perfect" rocker is one that transfers the cam information to the valve with the least amount of wasted motion or losses. You call this ratio change, but it is not. It is simply the result of angularity introduced into the system through arc motions. No matter where you check the rocker in it's rotation around it's axis, the lengths remain the same. (Have you watched the video I linked to yet?) A perfect transfer of cam lobe information wouldn't use a rocker arm at all. Overhead "bucket" type cams come to mind.

                        Using your logic, a small block Mopar, which does not have a pushrod that follows the trajectory of the lifter (it's on a different angle), the loss of lobe lift at the end of the pushrod would mean that the lobe is getting smaller, therefore, less lift. That would be utter nonsense, but somehow, because you see losses at the valve, all of a sudden the rocker arm is losing ratio, and the fulcrum length is getting longer or shorter. Utter and complete nonsense. It is called Trigonometry. You have to understand what the "whole" system is doing before you can attempt to make a better rocker, or make a claim that someone who does understand the system is wrong. Back up through the system to see where the losses actually originated, instead of automatically assuming the ratio changed. This is where Smokey went wrong. He observed a loss at the valve, and then noticed the fulcrum sweep which led him to conclude there was a ratio change. He never investigated beyond the fulcrum for the origin of the losses. Had he done that, he would have found that pushrod/cup angularity, from sweep and rocker design, was reducing the input, and thereby, reducing the output as well.

                        Ok, you keep beating this old nag. Just shoot her and put her out of her misery. There is no valve side ratio or pushrod side ratio. But, because you insist, here is a test question for you.

                        Henry has a Jesel NASCAR SB2 rocker arm that has a .545" roller tip and has a 1.620" fulcrum length and a .575" offset. What is the ratio of this rocker? (For informational purposes only. Specifications are random, and do not necessarily reflect an actual Jesel SB2 rocker arm.)

                        If you want something to really make your head hurt; (this may not seem relevant, but it really is)

                        Three salesman travel to New York for a large conference. When they try to find a hotel room they find they are all booked. Finally they stumble across a budget hotel that has one room left, so they decide to share it. The young man at the counter tells them the room is $30, so they each pay their $10 and go up to the room.

                        Meanwhile the hotel manager comes back from a lunch break, and the young man tells him he rented the last room to three salesman. The manager asked how much he charged and the young man replied $30. No, no says the manager, that room is only $25. Take $5 up to the room and return it to the salesmen.

                        On his way to the room, the young man is thinking, "how am I going to divide $5 among three salesmen"? "I know", he thinks. "I'll give them each one dollar and pocket the other two." So, that's what he did.

                        So, the question is, If initially the three salesman each paid $10, for a total of $30, and they each got back $1, then they each paid $9. 9x3=27, so they paid $27 for the room. The young man pocketed $2. $27+$2=$29. If they initially paid $30, then what happened to the missing dollar?
                         
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                        • 80fbody

                          80fbody Well-Known Member

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                          So, how does any of this help the OP pick a rocker arm?
                           
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                          • AndyF

                            AndyF Well-Known Member

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                            I gave the OP all the information he needed to pick a set of rocker arms back at the beginning. The rest is just a rehash of an old argument that had been going on for a long time.
                             
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                            • IQ52

                              IQ52 Well-Known Member

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                              Agree with Andy in that the OP was fully answered and the answer confirmed by the end of post #42.
                               
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                              • yellow rose

                                yellow rose Overnight Sensation FABO Gold Member

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                                At post 16 the answer was given. Then we had some discussion and then it went to hell.
                                 
                              • B3RE

                                B3RE B³ Racing Engines

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                                Maybe, just maybe, with more information the OP, or anyone else for that matter, can make a more informed decision.
                                 
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                                • RustyRatRod

                                  RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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                                  Trust me. You're not the one chasin it. You caught it years ago. Decades, perhaps.
                                   
                                • B3RE

                                  B3RE B³ Racing Engines

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                                  I don't recall the OP only wanting one opinion, and you are dismissing others who gave their opinion with that statement. If that was the case, he could have just sent you a PM and not bothered with starting a thread.

                                  But, what I really want to know about this old argument is, Am I Wrong? You have an engineering degree and I assume know all of this stuff.
                                   
                                • B3RE

                                  B3RE B³ Racing Engines

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                                  Sorry, but I think you've made a lot of claims.
                                   
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