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

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Rapid Robert

Rapid Robert

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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
 
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.
 
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
 
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.
 
Marcohotrod said:
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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Only a knothead would interchange 5/16 and 8mm locks. This is another place where a .0025" difference can kill an engine.
 
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.
 
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.
 
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
 
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!
 
Marcohotrod said:
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!
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Marco I will check the valve groove against the lock groove. What is a bead lock?
 
Does anybody make an 8mm 10 degree Chevy style square lock? Manley makes a nice selection of 5/16 10 degree beadlock locks.
 
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
 
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.
 
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Rapid Robert said:
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
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Tnx for the follow-up info RR
 
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.
 
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PRH said:
What valves are you using, and how far is it from the top of the lock groove to the top of the valve?
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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
 
.050" from lock to tip.
Click to expand...

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.
 
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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