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MG MGA - Valve Clearance Lock-nut

In the UK we usually call it the tappet adjustment lock-nut.

Does anyone know the exact size of this lock nut? Is it definitely an AF size?

I have always used a 1/2" AF ring-spanner on these nuts.

I have a few in this size but all of them are a little loose, some of them so loose that they slip if you are not very careful. (I still have the scars on my knuckles to prove this.)

It may be that my ring spanners are just poor quality ones although they are a recognised make.

I like to check the valve clearance quite often on my engine and so your input would be very welcome, if only to prevent any further blood loss :-)

Cheers
Colyn.


Colyn Firth

They are 5/16 UNF half nuts and yes, a 1/2 spanner fits them.

Being only 1/2 height they tend to get damaged over the years by spanners slipping - one trick is to turn them upside down.
Chris at Octarine Services

5/16-24-UNF thread, 1/2-inch wrench size. They are jam nuts, not holding the wheels on, only intended to keep the screw from coming loose. Take it easy, tighten it with a short wrench and your fingers so as not to stretch the threads out of the nut. If you scrape your knuckles undoing it, the last bloke made it too tight.
barneymg

I really must have a strong word with that "last bloke"
Barney, the only worry I have is what my wife will say when she hears me talking to myself :-)

Maybe I should also get rid of that 3 foot long tommy-bar I use on the spanner! :-)

I have started to look for a better quality ring spanner that fits the lock-nut better, it will probably save money in the long term, on band-aids alone!

Thanks Chris and Barney

Colyn
Colyn Firth

Colyn
Some of the cheaper spanner sets use the same spanner for 1/2' and 13mm but stamped with either size
1/2" is roughly 12.8mm so these 13mm dodgey spanners are a bit loose even when new
A good quality 1/2" should fit better
willy
William Revit

Colyn could you drop me an email please scuderiablkholeATaolDOTcom.
Its about seat angles and wedges...
David
David k Brenchley

Thanks Willy
I have sent for a short deeply cranked ring spanner, it is a 1/2"AF by Britool.

Probably it is a cheap copy of the original Britool and will be no better than I already have.

Will let you know and send a report on the state of my knuckles once I have tried it out.

Will email you David
Cheers
Colyn
Colyn Firth

How about a six sided 1/2 socket and sliding tee bar handle for loosening and the final nip up - works for me.
Mike
Mike Ellsmore

Colyn. A to deeply cranked ring spanner will tend to slip off the adjuster nut more than one with a gentle crank,the two on the right work better, the one second from the left is more prone to slip off than the other two, if the are really tight I use the socket spanner on the left to just crack them loose, a thing to remember is they only need nipping up, you don't have to swing on them,


Andy Tilney

Time for the all inclusive Click Adjust Colyn! It's only got a 5.5" arm instead of your 36" crow bar.

Steve


Steve Gyles

I have got one of those gadgets somewhere in a box Steve, they seemed to be a good idea, particularly on the skinned knuckles front.

I have tried it but the instructions seemed be a bit vague.

Each time I used it the valve clearances seemed to vary by about a thou or two.

So I have stuck with feeler gauges, I seem to get a more consistent result with them.
(I will just have to put up with the blood loss! :)

Cheers
Colyn
Colyn Firth

Colyn. In truth I agree totally. I dug it out for a bit of fun.

Steve
Steve Gyles

I have just had this ring spanner delivered, its a Britool(or at least it is marked with that logo). A kind of early Christmas present from me to my knuckles😁.

Seems to be decent quality, time (and knuckles) will tell😊.

Have a great Christmas everyone
Cheers
Colyn


Colyn Firth

Nice opticians ruler. Racking my brain to think of alternative uses on the MGA.

Steve
Steve Gyles

Absolutely the right tool to use. Those "short" offset box end wrenches have been hard to find in recent years, but wonderful for the traveling tool kit.
barneymg

He's a good looking little fella, should do the job nicely
William Revit

This thread was discussed between 12/12/2017 and 23/12/2017

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