15 replies to this topic

[mattbeddow]

Went to adjust the rockers today as i noticed they were way too loose the other day.
7/8 of them went fine but the previous owner has had a go at doing it in the past and had rounded off one of the nuts that locks the adjustment screw into place so i cant get it undone.
Any ideas?

[hawky443]

cold try masking off all the rockers and cutting a slit in the head of the screw with a hack saw?

[Cooperman]

cold try masking off all the rockers and cutting a slit in the head of the screw with a hack saw?

He said the nut was rounded, not the rocker adjusting screw.
If the nut won't come off, you could try knocking a 12mm socket on then undoiing it and fitting a new nut. If that is not possible, you could drill down through the edge of the nut, then split it with a chisel to get it to undo. Or a stud-extractor might work across the threads of the nut.
If all else fails the shaft will have to be removed from the head, then the nut 'grabbed' in a vice and the shaft rotated to free it.

Edited by Cooperman, 17 June 2012 - 11:08 PM.

[tiger99]

Once you get it off, you will want to avoid it happening again. As far as I can tell (and yes, I have had problems with these nuts), it starts because the nuts are quite thin, and one of the readily available adjusting tools (I think it is Draper) uses a socket to do up the nut, with a built-in screwdriver bit to rotate the screw. Those tools are great, because they allow setting very quickly, just by counting clicks, but the use of a socket causes problems, because the entry on a socket is tapered for easy location on the nut, and because of the taper it may only be gripping on half the width of the already thin nut.

I got a new, fairly tight socket of the correct size, and ground the end to remove the tapered part, so it gripped the full width of the nut. It does not go on so easily, but is useful anywhere that a nut is proving to be difficult.

If doing them in the more conventional manner, with feeler gauges and screwdriver, I use a short ring spanner, which has very little taper, and grips adequately.

Oh, and the nuts are imperial, not metric, and a metric spanner will chew them.

[dklawson]

My suggestion is to buy a new nut before attempting any removal of the rounded one. At least with this one arm/nut seized you know the engine runs and you can drive the car.

Once you have the new nut, don't plan on saving the old one. Use a pair of mole grips to tightly grab the old nut. Apply torque first to tighten the nut, then to loosen. Keep pushing and pulling on the wrench until the nut and adjusting screw break free. Once free, run the old nut all the way off the screw and fit the new nut and adjust the valve.

Like Tiger, I use a "box end" or ring spanner when adjusting valves. They grab well and will typically not cause the damage that an open end wrench will cause. I have never even thought about sockets as I hold the screw with a screwdriver (so it won't move) while tightening the nut. However, I use a long handled wrench not a short one.

Side note on why I use long handled wrenches.
My father-in-law vintage races a Formula-Vee. I do his major mechanical work and work as crew. Recently he prepared the car for a track day where I could not go with him. He came home complaining that the car had lost power and he didn't understand why but he noticed the engine seemed a bit noisy. It turned out he had adjusted the valves and used his "stubby" wrenches to tighten the valve adjusting nuts. The stubby wrench was short and didn't allow him to fully tighten the nuts. On two cylinders the nuts had vibrated loose and the valves came completely out of adjustment. Basically, he was running on 2 cylinders out of 4 by the time he brought the car in. Anyway, I have always used long handled wrenches to allow me to tighten the valve nuts fully. This is just an example of what can happen if you don't apply enough torque.

[mattbeddow]

i thought there wouldve been a torque setting for these in haynes but there isnt, just says "tight"
I thought they were imperial too but my 1/2 af was too big and the 7/16 too small.
Found a 13mm fit much better and worked on all the others.
Where can i buy a replacement? do minispares have them and what size do i need?
I definitely dont want to break it off if i cant get another

[dklawson]

See this product link page at Mini Spares...
http://www.minispare...eads/6K654.aspx

The link lists not just the one nut but others that may be appropriate. Note that the thread is NOT a UNF thread, the nuts are special. If there is insufficient information on the product pages at Mini Spares I would give them a call to discuss the parts to help identify which nut you need.

I have never seen a torque listed either. As I mentioned, I have always used a screwdriver to hold the screw while the nut is tightened. That in itself would prevent use of a torque wrench as you couldn't pass the screwdriver through the wrench's drive mechanism. In this case... "tight" is as good a torque spec as you will find and it is why I use long handled wrenches.

[mattbeddow]

Thanks, ive ordered the larger 1/2" spanner nut as the 7/16ths spanner was too small so im hoping this is the right size.
I found when doing the others that the screw turns 1/8th of a turn when it is done with the ratchet so i set the correct gap, backed it off a little and then tightened it and it was spot on.

[Ethel]

Ooo does that link suggest we're set for another thread type topic

13mm is actually a bit bigger than 1/2".

A surface drive spanner, or socket, may make just enough difference & turning the screw and nut together will also help.

[mattbeddow]

Yeah i thought that too but even in my socket set, the 7/16 was too small and the 1/2 span on the first one but the 13mm took them straight off no bother.

[dklawson]

Ooo does that link suggest we're set for another thread type topic

A thread about threads? No... I think Tiger and I exhausted that topic last time.

[Cooperman]

i thought there wouldve been a torque setting for these in haynes but there isnt, just says "tight"
I thought they were imperial too but my 1/2 af was too big and the 7/16 too small.
Found a 13mm fit much better and worked on all the others.
Where can i buy a replacement? do minispares have them and what size do i need?
I definitely dont want to break it off if i cant get another

A 13 mm is actually bigger than a 1/2". A 1/2" is 12.7 mm.

[tiger99]

Your 1/2" spanner must be very seriously worn if a 13mm was better.

As for threads, which Doug and I seem to like "discussing", I assume it might be a 5/16" UNS (S=special), i.e. it will have the standard thread profile used on UNF, UNC and even metric threads (60 degree angle, with certain proportions for root and tip radii/clearances), but a non-standard pitch. But that assumption may be wrong, because the early A series in the Morris Minor etc used BSF in many places, with a 55 degree angle, and different root and tip clearances, and it may have been carried over into the Mini, with only proper AF hexagon size as the difference.

Most of us don't need to know the details and will just buy the correct nut, but one day, when the supply of spares dries up, people with machining facilities will be making them at home, so when that day comes we will need to know the actual spec.

As I said earlier, I use a shortish spanner, actually a combination type, but I do apply a LOT of force, so they are really tight. I gave up on the long ring spanner because it had a large offset and wanted to slip off.

[dklawson]

The offset can be an issue and does require some care when using regular ring spanners. There is a product called a tappet wrench. They are thin and have straight heads that are "flat" with the handle. However, I have never seen them in ring-form. They have always been open end so I have never bought a set.

Speaking of weird or unique threads, I found one recently that surprised me. I found that Stromberg carbs have butterfly shafts that are 7mm in diameter so they threaded the ends M7x1. I suspect SU carbs are the same.

[mattbeddow]

I know im fairly new to actually working on cars but i never thought it would take 1.5 hours to get that ba**ard off!