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MG Midget and Sprite Technical - Replacing rockers without lifting the head

Is it possible to replace rockers on my A-series midget without going 'the whole hog' and replacing the head gasket? I have a recollection that Peter Burgess said on this BB that this is possible but I can't find the thread in the Archives.

On a related point, I have forgotten the torque setting to head studs 10 and 11 (I have an 11 stud head). Is it 25 ft/lbs?
Chris Hasluck

Perfectly possible - drain the coolant level to below the head gasket then slacken off the head nuts in the correct sequence and retighten to 20 ft lbs as you go round. Then undo the nuts holding the rocker shaft assy, replace the assy and nip up the nuts to 20 ft lbs. Finally retorque to spec and adjust the valve clearances. Refill coolant and you are done.

I haven't heard of tightening the standard head nuts to anything other than 45 ft lbs, whether 9 or 11 studs.
Chris at Octarine Services

Chris H - yes, studs 10 & 11 should be no more than 25 lb ft. The one next to the thermostat housing usually breaks through into the waterway so there isn't a huge amount of thread for the stud to engage with. Some engine builders will use a bolt at this position.
David Smith

If it's just the rocker arms you are replacing , you don't have to let the headstuds go
Loosen off all the adjusters as far back as you can
Remove the splitpin and washer from both ends of the shaft, push down on the valves if you have to and remove the two rockers,
Poke a small X head screwdriver through the front s/pin hole, remove the shaft locating screw and use the screwdriver to wriggle/twist the shaft forward, removing the rockers as the shaft comes out through them
Reassemble in reverse--you might have to turn the engine over to get one or two started on the shaft but easier than pulling the head off-
Works fine on a B series and can't see why not on an A
willy
William Revit

The original 11-stud heads did use a 5/16” bolt by the thermostat, which was definitely 25lb/ft. I can’t remember without looking what the rearmost (3/8”) stud should be torqued to.
Dave O'Neill 2

Probably not "recommended" but I have done this several times on various A series engines by simply undoing the 4 pedestal nuts and lifting the rocker shaft off, leaving the other head bolts undisturbed. The cast iron head is rigid enough to maintain its clamping pressure evenly across the full width if it isn't disturbed - it's not as if you have the compression and firing of a running engine whilst you do it.

After refitting the rocker shaft I then go round and one at a time slacken and retorque all of the nuts in the usual sequence.
GuyW

Thanks for the comments. Much as I thought so I'm now waiting for a warm(er) spell of weather to go out in the garage and do the job.
Chris Hasluck

We do it the same way Guy, slacken off the 4 rocker studs only and we do not retorque the untouched other head studs. We do this more frequently on MGBs when we are changing a cam in situ. Never lost a head gasket in 32 years!
Peter Burgess Tuning

I had to do this job last November - swapping rockers between the Frog and the Mk IV. I read all the previous threads about it and followed the advice above. The MkIV was fine, lost the gasket on the Frog. I've no idea what I did wrong - if anything.
Paul MkIMkIV

I did exactly this, to minimise strain on the head, I loosened all the studs by a small amount, then replaced the rockers (roller rockers went in) and torqued them all back up and it's been fine.
R Cohen

This thread was discussed between 17/01/2019 and 13/02/2019

MG Midget and Sprite Technical index

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