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MG MG Y Type - Valve stem seals (o-rings).

Someone somewhere once said "If you want something done properly ...". Might have been Shakespeare.
Buttoning everything up after recent engine-out episode, I looked at the top of the head and saw a little rubber o-ring sitting on the bench - the rest sitting where engine-builder (retired) put them (see pic) - on top of the valve spring cap. From my reading, those little rubber o-rings should sit under the split collets, where they can do a reasonable job of stopping oil running down the inlet valves.
Where they currently sit, they don't do a thing ... not a sausage.
So - as part of my learning process, I'm hoping those overhead valve spring compressor things will enable me to remove & replace correctly. Presumably with each piston at tdc for obvious reasons. OR - take the head off and use the clamp style compressor. Any thoughts folks?
Thanks as ever. John.


J P Hall

Hi John,
Yes, they should be jammed in under the collets. They can be fixed without removing the head. One way is to deliver compressed air via a fitting in the spark plug hole before using a spring compressor to do the job.
The other way is to feed clean rope into the plug hole and then turn the engine over gently until that rope is compressed up against the valves. That is the only way I have done it (a long time ago). Sometimes you need a second try at feeding in the rope because a wad gets jammed between the flat edges of the cylinder head and piston, instead of valves and piston.
I am not sure of this, but be aware that an un-tethered inlet valve might be able to drop down a bore, depending on valve and bore size. Not a problem with exhaust valves because they hang over the edge of the block face a fair way.
Good luck with the job.
Bob
Bob Schapel

Hi Bob
Far out John--you have all the fun
Bob's got it covered.
The overhead (cork puller) style spring compressor will do it but most of them haven't got long enough fingers on the ends of the arms to reach in far enough to reach the inner springs--I had to build up some longer tips on mine to get it to work properly---others might be different--mine is a KD tools 2078
Because you don't really need to take the spring right off to do this job you could make up a tool
I've used a 12" shifter in the past---Centre the hole in the end of the handle up with the valve stem and measure out to a rocker gear bolthole in the head and drill a hole in the handle of the shifter, --then you can poke a bolt through into the head ,poke a packer (piece of wood) under the other end of the shifter and use the bolt to wind the spring down-----Doing it this way you don't have to hold anything while you remove the keepers, fit the o ring and refit the keepers--then let it up
just a tip--as you're doing it withj the head on and can't get at the valve head for support----as you start to get a load on the spring cap, give it a little tap with your favourite hitting thing just to release the cap from the taper of the keepers----but you will need either rope in the hole or a decent piece of suitably bent wire to hold the valve up in place----IF you're going to do it with compressed air in the cyl you need to have it dead on tdc, in gear and the handbrake on to keep the motor from spinning over to bdc
And you need to do all 8, not just the inlets as some would make you believe is ok
what's next-?
willy
William Revit

I am truly blessed - great advice from two of the most experienced xpag men on the planet. Thank you Bob and Willy. The way forward is clearer, and I do have access to the sparkplug fitting in the event that I try the compressed air approach. Just one thing - what's the downside to taking the head off and just doing the job on the bench? The head has of course been given its initial correct torquing, so some compression to the new head gasket - but the engine has been sitting waiting for me to finish the rest of the restoration since it was built 4 years ago; maybe just another new head gasket?
Decision time! Thank you both.
John.
J P Hall

Nothing stopping you taking the head off--possibly easier way to go if you haven't fitted the manifolds etc. yet---but it's not a major undertaking either way
If the head is still naked I'd be tempted to pluck him off and do it on the bench----or not 50-50 choice really
seeing it hasn't been run yet I'd use the headgasket again--it won't

So just to get this right--
You have to compress the spring/cap down
Fit the o ring on the stem--fit the keepers, they're usually a bit of a springy interference fit against the o ring
Then let the spring/cap up to wedge the o ring between the cap and the stem,up against the bottom of the keepers
I've seen heaps where the o ring has been fitted on the stem first then the spring and cap fitted which pushes the o ring down the stem----DON'T do that

willy
William Revit

Willy, the head is naked, so easy to remove. Your instructions are clearer than those on the NTG site (which are themselves not bad) - great help. I lean towards doing it on the bench.
What other hobby (in my case) gives you so much fun!
I'll report again soon. Hope this is of interest to others. Priceless to me.
John.
J P Hall

This thread was discussed between 28/08/2022 and 30/08/2022

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