8MM retainers/locks on 5/16 valves: OK or not OK?

Discussion in 'Small Block Mopar Engine' started by Rapid Robert, Nov 24, 2018.

  1. Rapid Robert

    Rapid Robert Well-Known Member

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    Lunati black 10 deg thick 8MM locks/retainers. Brain fart here, I thought my valves were 8MM & they are 5/16. Will this be an issue & if so do both (locks/retainers) need to be replaced with 5/16 units. 360 SB & EQ heads. Will be raced. Was ready to go together when I discovered this (when 8MM lash caps were a loose fit!). Thank you for your time. RR
     
  2. toolmanmike

    toolmanmike FABO Staff Staff Member FABO Gold Member

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    Get the correct ones.
     
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    • Rapid Robert

      Rapid Robert Well-Known Member

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      That was fast! Will do, when Lunati opens Monday.
       
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      • IQ52

        IQ52 Well-Known Member

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        With Comp Cams all you would have to do is replace the locks. I think that Lunati will be likewise. As you are going to call Lunati, just ask about locks only.
         
      • Marcohotrod

        Marcohotrod Well-Known Member

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        I only see lunati has 8mm ls1 bead locks. what valves do u have , ask them and lunati. 5/16" = .3125", 8mm = .315", I think they are interchangable, especially with a hydraulic lifter
         
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        • Rapid Robert

          Rapid Robert Well-Known Member

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          Yeah there is only several thou diff. these are 5/16 valves for sure (miking at .311"). the Lunati 8MM retainers/locks "appeared" to fit nice & I wouldn't have noticed any potential issue at all till I set the 8MM lash caps on em during my last mockup before final cleaning (& not sure I was even gonna use em after Mike at B3 raceing said not to) but the stud chebby roller rockers are too close to the ex side edge & I wanted to solve that if I could without some special $400 rockers then I saw all the play & knew there was a problem somewhere. EDIT hyd cam/6200 RPM/30 minute feature duration races. MORE EDIT I saw the CC retainers in the speedway add where they say it fits em both, just need diff locks as you said.
           
        • IQ52

          IQ52 Well-Known Member

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          Only a knothead would interchange 5/16 and 8mm locks. This is another place where a .0025" difference can kill an engine.
           
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          • Marcohotrod

            Marcohotrod Well-Known Member

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            single groove locks are not butting up against each other, there is what - .050" gap? now like I said-if he has LS1 8 mm bead locks-not for single groove standard 5/16" valves.
             
          • Rapid Robert

            Rapid Robert Well-Known Member

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            Between now & Monday I am gonna see if I can find my Lunati receipts for the locks/retainers (I will). I'm sure at the time that I told em that I had Mopar magnum 8MM valves.
             
          • Rapid Robert

            Rapid Robert Well-Known Member

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            I spoke with Lunati several hours ago. My retainers can be retained, just need new locks which I ordered. #77110-16 $27.19 thanks guys!
             
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            • Marcohotrod

              Marcohotrod Well-Known Member

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              the lunati website does not show 77110-16. what did they say about the 8mm ones u have?
               
            • Rapid Robert

              Rapid Robert Well-Known Member

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              Yeah I saw that myself, that there were no 77110-16's on their site but I spaced that for some reason but today I was thinking that it'd be good to know the part # of the retainers I have (just for reference as my note taking is woefully inadequate) so I am trying to rectify that so I called Lunati & got an older tech who fielded my Q then he saw my flagged order for the 77110 locks & informed me that they cancelled the order because those locks that the young tech picked out yesterday are the wrong ones & that the retainers (75740-16) & locks (77132-16) I currently have are absolutely OK for my 5/16 valves IF the locks are not butted around against each other when installed (which they were not). He sounded extremely sharp & swore up & down that I am good as is! That is the latest. RR
               
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              • Marcohotrod

                Marcohotrod Well-Known Member

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                I agree , like you said the original locks fit well, with gap , and a 5/16" lock is so close in size to 8mm that they can be interchanged-IF the are for the same style of groove in the valves. that is why I questioned what style grooves u have, cuz Lunati lists the 77132 as GM LS1 bead lock-not the old standard single channel groove!
                 
              • Rapid Robert

                Rapid Robert Well-Known Member

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                Marco I will check the valve groove against the lock groove. What is a bead lock?
                 
              • Marcohotrod

                Marcohotrod Well-Known Member

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                bead locks and bead lock style valves are half round, most single groove stuff is half a rectangle
                 
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                • IQ52

                  IQ52 Well-Known Member

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                  Does anybody make an 8mm 10 degree Chevy style square lock? Manley makes a nice selection of 5/16 10 degree beadlock locks.
                   
                • Marcohotrod

                  Marcohotrod Well-Known Member

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                  Rapid Rob has 5/16" valves, I wonder what style grooves they have?
                   
                • Rapid Robert

                  Rapid Robert Well-Known Member

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                  Marco that is a good definitive descrip. I will get out there in a day or so.