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

Small Block Mopar Engine

  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.
         
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        • 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.
                     
                  • Rapid Robert

                    Rapid Robert Well-Known Member

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                    I had a good conversation with Mike at B3 racing yesterday & he emphatically stated that the Lunati older tech was absolutely wrong in informing me that my Lunati 8MM locks will be fine on my 5/16 valves. I just now got off the ph with Summit & ordered Manley locks #131518 the only ones he said were available with bead locks as opposed to square groove. I has just noticed that with a valve/retainer/locks in my hand holding them "locked" that I could move the retainer up & down ~.020" so I knew sumpin ain't right. Thanks guys
                     
                  • PRH

                    PRH Well-Known Member

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                    What valves are you using, and how far is it from the top of the lock groove to the top of the valve?

                    The magnum style valves I have here have a single bead lock groove, and the top of the groove is .120 from the top of the valve.

                    I’ve never run across any 10* locks that would work with this style of valve(they might exist, I just haven’t seen any).

                    The LS “style” of lock is correct(bead located at top of lock)....... if you could find one that fits a .311 valve

                    Manley 13151-8 should require a tip length of about .190-.200 minimum.
                     
                    Last edited: Dec 20, 2018
                  • nm9stheham

                    nm9stheham Well-Known Member

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                    Tnx for the follow-up info RR
                     
                  • PRH

                    PRH Well-Known Member

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                    Not a lot of guys using oe style magnum heads much these days, but it looks like the easy work around for the semi-oddball lock situation would be to just use Chevy LS valves(if it’s an application where the stock magnum locks and oe or MP retainers won’t suffice).

                    Hone the guides to fit the slightly larger stem diameter, then the retainer/lock situation gets easier.
                    The “.100 long” LS valves would also give you a little more installed height over the OE length valves.
                     
                    Last edited: Dec 21, 2018
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                    • Rapid Robert

                      Rapid Robert Well-Known Member

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                      I ain't sure what valves I used (way too many projexts going on combined with poor record keeping!) but they are 5/16 with bead lock (rounded bulges) in genuine new zealand EQ heads. .050" from lock to tip. NOW the prob I am haveing (discovered today) is the comp cams 4825 guide plates were mfr'd so terrible that the 5/16 pushrods wont even fit in the rectangle slots let alone have 5 tho clearance on each side. In the set of (8), at least 5 had one slot that was too small. A guy at Summit is gonna work with me next week to trial fit a set there before they ship em out. I did not get mine from them tho. RR
                       
                    • PRH

                      PRH Well-Known Member

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                      That doesn’t really tell me anything.
                      Depending on what locks were used that number can change.

                      What I’m looking for is the dimension from the top of the lock groove that’s cut into the stem of the valve, to the top of the valve.
                       
                    • PRH

                      PRH Well-Known Member

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                      I’m sure everyone knows what the stock magnum valves/retainer/lock situation is...... I’m just using this as a test pic upload.

                      97EF0208-C2A1-4351-9CC5-5EB01E459EEB.jpeg

                      B96BC95F-B849-491D-8A44-28FF07020449.jpeg

                      62C0C6A4-6BAA-44E6-BA9F-3775007781A1.jpeg

                      58966776-CB7E-431D-8491-961FD3F92D9C.jpeg
                       
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