Rocker assembly query

[Chappers]

Oh dear, had a bad day with Maisie today...
Just thought I would check and adjust the valve clearances before taking her out for a drive in the sun.
Had adjusted the clearances some time ago and noticed that the adjuster screw and locknut threads felt stretched, and the state of both suggested they had been overtightened in the past by previous owner/s.
Confirmed today when halfway through the adjustments one of the threads finally let go.
It looks like the adjuster thread has stripped but the locknut thread looks awful too.
So far on the car, I have found many things only lightly tightened, but some heavy handed Ape has been doing the valve clearances

Guess which one it was

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Have ordered a new set of adjusting screws and locknuts, but can someone advise/confirm on the following please?
The Rocker shaft is held on by 2 sizes of nuts, the larger I presume are cylinder head nuts.
Here’s my plan;
Undo Rocker pedestal nuts, then loosen in sequence the cylinder head nuts on the Rocker pedestals.
Remove rocker shaft assembly, and measure distance from bottom of rocker (adjacent to adjuster) to end of adjuster ball.
Remove old adjusters and replace with new, setting to measurements taken before disassembly, to provide a “starting point”.
Replace rocker assembly and hand tighten securing nuts. Tighten Rocker pedestal cylinder head nuts in sequence, then the remaining Rocker pedestal nuts.
I realise they have different torque settings.
Then check and adjust valve clearances.

Would you recommend slackening all cylinder head nuts?
I don’t plan to remove the head, just the Rocker assembly.
Do the head nuts need checking and re-torquing after running the engine to full temp?
Any comments and suggestions most welcome.

[philthehill]

To replace the adjuster screws you do not have to remove any of the rocker pedestal nuts or cylinder head nuts.

Put the cam follower on the back of the cam lobe to give max clearance - slacken the respective rocker nut & screw right off and disconnect the pushrod from the adjuster screw - slide the rocker to one side and twist - remove the screw - fit new screw and nut and reverse procedure - when all done adjust rockers as normal.
The end rockers may require the split pin to be removed to allow the rocker to move sideways - but that is not difficult.

All fiddley but doable.

If the threads in the rocker require cleaning a BSCY (cycle thread) 9/32" x 26TPI tap is what you require. The threads are UNS (unified national special) but a BSCY tap has the required profile to clean but not cut a new thread.

Make sure that the replacement screws are not centre drilled to allow oil to reach the push rod. They are also waisted and that is a weak spot.

[Chappers]

Phil,
You’re a genius, this is what makes the forum so great!
I’ll have another look at the rocker assembly in the morning, thanks.
Pretty sure I have ordered the “plain” adjuster screws, but I won’t know until they arrive in a few days time.
Always a good idea to avoid unnecessary disassembly.
Appreciate your quick response.
I will let you know how I get on...
Regards and many thanks indeed,
Mark

[Chappers]

New tappet adjuster screws and locknuts arrived today, and fitted this evening.
All changed as per Phil’s instructions, really easy job overall.
Maisie is all running sweetly again.
Once again, many thanks for your valuable advice Phil, which was very much appreciated.
Regards,
Mark

[MikeNash]

I see that Mr Chappers' valve collets have wire clips around the collets' outer grooves. I've never had these fitted to any of my "A" series engines and, indeed, they're not part of any other make of engine I've had. Are they important?
Regards from MikeN.

[philthehill]

Mike
BMC fitted the clips as a 'Belt and Braces' solution to stop the retainers valve cap (collets) falling out at high engine revs.
The clips were also fitted on other BMC group engines.
The clips soon lost their spring ability to retain the collets and many were lost or discarded.
Improving the quality control processes and fit between collet and valve spring cap allowed the clips to become redundant.
The shroud - guide and oil seal retainer also became a non item.
So to answer your question:-
The clips are not important when the engine is used for normal driving but if you use higher rev limits than normal the original standard valve caps and collets should be replaced with the later better quality items.
It should be noted that not all valve collets and valve spring caps are interchangeable - they should be matched to the valve, valve spring cap and the type and number (i.e. double) of valve springs fitted.
See BMC wksp man section AAA.7 for more details.
Phil

[MikeNash]

Phil,
Thanks for the advice and reference; as my 1098 is a ordinary road machine I shouldn't have a problem. I'll remove the shrouds as well 'cos I find any oilseal on the valves always breaks up whatever type. See the picture below that I've just taken. And the shrouds weigh almost 6g each which at the point where they're fitted is worth getting rid off.
Finally, I'm going back to the pressed rockers like Mr Chappers has and wonder what your views are on the use of spacers instead of the springs and washers that are used in the normal arrangement on the rocker spindle.
Regards from MikeN.
(Sorry to jump in on your thread, Mr Chappers!)

[philthehill]

Mike
The top hat seals as shown in the photo should not be used with the shrouds (Pt No: 2A544)..
If you want to use the top hat seals you should discard the shrouds and just have the spring top cap (Pt No: 2A10).
With the top hat seals it is better to use the valve guide with top hat seal locating groove - available from ESM.
http://www.morrisminorspares.com/engine ... l-p1209547
Use of the spacers between the rockers is a good move as you can with shims centralise the rocker over the valve stem which reduces wear of the rocker shaft and the hammer tip of the rocker.
http://www.minispares.com/product/Class ... sic/rocker spacers.aspx|Back to search

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100_2636.JPG (1.71 MiB) Viewed 1959 times

[MikeNash]

Thanks for that, Phil. I'll get and fit those spacers; I like to have simplicity and minimum friction in valve gear.
Re the oil seals I remember now that their installation it was a bit experimental. I felt that the complication of fitting new valve guides to locate the seals was a step too far but that probably assisted in their failure. The alternative, called "packing rings" in the Section AAA.7 of the manual and installed below the collets and inside the shrouds I've also found to break up and disappear and so I'll run without any seals and see how I get on. I don't expect trouble.
Regards from MikeN.

[philthehill]

Mike
Top hat seals only need to used on the inlet valves so as to stop oil being sucked into the manifold.
With unleaded fuel the exhaust valve stems need all the lubrication they can get as unleaded fuel is 'too dry' in that it has very little if any lubrication qualities which can cause the valve stem to pick up and stick in the valve guide.
The little 'O' ring packing seals are next to useless and you will see little difference whether they are fitted or not. Only the top hat seals are effective.
Phil