273 rocker push rods

Small Block Mopar Engine

  1. bbab3

    bbab3 Well-Known Member

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    I am in the process of finding the proper push rod length for my SB with 273 rockers and a hydraliclic cam. My question how far the stock adjuster need to protrude from the bottom of the rocker arm. Thanks
     
  2. Plymouth 65

    Plymouth 65 Floorable Deplorable

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    Was the block decked or heads shaved? Adjustable rockers typically have 1-1.5 threads protruding out. 65'
     
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    • bbab3

      bbab3 Well-Known Member

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      It was decked and has Edelbrock heads and new a new cam. Tried a set of Melling mrp-157 7.234” push rod for the 340 t/a motor and they are almost touching the rockers.
       
    • Plymouth 65

      Plymouth 65 Floorable Deplorable

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      Get an adjustable pushrod length checker. Have Smith Brothers make you a set to your measurement. 65'
       
    • 4spdragtop

      4spdragtop CONGRATS NORTH AMERICA! FABO Gold Member

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      I'm no help but if you post pics will help me learn lol. Beautiful color choice on cuda by the way!:thumbsup:
       
    • 4spdragtop

      4spdragtop CONGRATS NORTH AMERICA! FABO Gold Member

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      I would also say that once you get pushrods, maybe think about a geometry kit? A member on here has them. I believe they're relatively inexpensive, and you've come this far??
       
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      • bbab3

        bbab3 Well-Known Member

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        I just made an adjustable push rod from a solid lifter push rod. Planning on checking each valve with the proper preload and averaging the lengths. Just want to have the correct starting point. I will take some pictures. Thanks for the compliment on the color.
         
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        • krazykuda

          krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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          Last edited: Nov 4, 2020
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          • RustyRatRod

            RustyRatRod Lemmie see your b00bs. FABO Gold Member

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            Jake has a set in the for sale section now that should work for you.
             
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            • bbab3

              bbab3 Well-Known Member

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              Krazykuda thanks for the list of threads. I have read most of them previously and am planning on contacting oe pushrods when I have better idea of the length needed. RRR thanks for the lead on the crane push rods. they they have a "working length" of 7.185, the Melling mpr-157 are 7.234. The .049 difference may or may not be what i need. As you can see from the photo this is how close the cup is to the rocker after setting the adjuster to zero lash plus one turn as per Racer Browns instructions. Also the cam is a Racer Brown EH-20 dur. @50 i220 e220 lift i.450 e.450. The geometry looks correct with the 7.234 push rods,




              image.jpeg
               
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              • toolmanmike

                toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                I would want another thread or two showing on the pushrod side. Just sayin'

                100_5228.JPG
                 
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                • Plymouth 65

                  Plymouth 65 Floorable Deplorable

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                  The pushrod cup edge appears to be too close to the rocker. May want to confirm the ball/cup diameters. 65'
                   
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                  • bbab3

                    bbab3 Well-Known Member

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                    The ball and cup diameters match up close to the factory solid lifter 7.500 rods. The 7.234 rods are just to long. Some would rub against the rocker and not achieve zero lash. From what I have found from searching different threads is that that the adjuster needs to be exposed any where from 1 to 2 threads or 1/4" to 9/32" to provide proper oiling to the push rod.
                     
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                    • toolmanmike

                      toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                      The 7.234 pushrods are a quarter inch shorter than the 7.500 ones
                       
                    • oldkimmer

                      oldkimmer FABO Gold Member FABO Gold Member

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                      7.500 r 4 the non adjustable hyd lifters. They r ball and ball. Kim
                       
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                      • krazykuda

                        krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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                        also check your rocker arms to make sure that they only contact the valve stem on the full stroke and not hit your valve spring retainers, we had to grind ours for some clearance...
                         
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                        • krazykuda

                          krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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                          You have different adjusting studs... I prefer the adjusting studs with lock nuts so they don't loosen up... They will last longer before needing to adjust valve lash than the non lock nut studs... But that can also affect the push rod length as they are longer, so decide on the adjusting studs, then figure out the push rod length... There should be about 1 1/2 threads below the rocker arm when the push rod is in and adjusted properly...
                           
                          Last edited: Nov 4, 2020
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                          • 4spdragtop

                            4spdragtop CONGRATS NORTH AMERICA! FABO Gold Member

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                            This is perfect example why I like pics. So many variables that can add up to cause issues. Tons of experience on fabo that spot problems in a pic. And like I mentioned pics help me learn lol.
                            You can see in tmm's pic how his adjuster sits in the rocker.
                            Lots of good advice here.
                             
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                            • bbab3

                              bbab3 Well-Known Member

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                              Well I measure each rocker and came up with an oal of 7.266 average, or a cup to ball length of 7.108.
                              Krazykuda, you mentioned using the nut locking style of adjusters. how much do the affect push rod length?
                               
                            • krazykuda

                              krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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                              It depends on the design of the push rod stud... Some have 'more ball' than others... (That's what she said.... :D )

                              It's the distance from the tip of the ball to the start of the threads that you need to watch...

                              Our pushrod ended up to be 7.064", see post #37 here and it also has pics so you can see the adjusting studs and nuts with the proper adjustment and 1 1/2 threads below the rocker arm...

                              Pushrod for hydraulic cam and 273 rocker arms

                              I would estimate that the locking nut studs are about .050" - .060" longer than the 'regular' stud without a lock nut, and going from the difference between your measurements and ours...
                               
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                              • Rocket

                                Rocket FABO Gold Member FABO Gold Member

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                                You may also want to check the clearance of the cup to rocker through the rockers opening and closing cycle to be sure you have no clearance issues between the cup and rocker body.
                                 
                              • gm1236

                                gm1236 Well-Known Member

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                                If you use the locking nut studs your going to have problems with them on a stock rocker. The top of the rocker where the stud goes through needs to be machined flat or the lock nuts will keep losing up. Crane studs with the Allen head is a good one to use if you go that route. If you want to stick with the iron rockers I would buy a complete set of new ones, with the locking nuts. Isky used to make them, as well as crane, how about comp? If this is a stock motor the 273 ones as is will work fine. I ran a combination of Isky and crane’s in a stock eliminator motor for years. I just took that motor out, they still look good.
                                The pushrod lenght doesn’t change your geometry in these motors, the rocker shaft to valve tip height does. About 2 threads out of the bottom of the rocker is what you want. It will give you the adjustment you need. If you have any questions pm me.
                                 
                              • Bodyperson

                                Bodyperson Pedal to the metal

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                                Wouldn't a ball and ball pushrod with a socket adjuster benefit pushrod angle here?
                                 
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                                • Bodyperson

                                  Bodyperson Pedal to the metal

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                                  Oh ya it's all coming back to me now. I read about it somewhere (most likely here) where you also offset drill the rocker for a bigger adjuster and move the pushrod too.
                                   
                                • bbab3

                                  bbab3 Well-Known Member

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                                  I talked to the owners son of OE Pushrods this morning (really nice guy) and began my order for new pushrods. Thanks, Krazykuda.

                                  Rocket, I checked the cups and springs for clearance when gauging the pushrod lengths. Pre-grinding the rockers for springs helped. The pushrod cups look good with the adjusters set at the proper position of 1 1/2 to 2 threads exposed.
                                  gm1236, The 273 rockers that I have look like they have very little wear to them. I talked to Jim from Racer Brown about using them with the factory adjusters. He felt the same as you that they should be fine with his ef-20 cam. I was a little skeptical about them since I once owned a '71 340-6 Cuda that had the lock-nut adjusters. I thought they made a change for a reason.
                                  Thanks both of you for the help.
                                   
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