Morris Minor Owners Club

I have a quandry...
I have the head off my 948cc Minor to replace a failed head gasket. I am almost ready to put the head back on but I thought I should grind the valves first. This raises the old chestnut of what to do about the valve stem seals. At this time, I would prefer to avoid upgrading the (intake) valve guides to the type with a groove to retain spring seals. I know that the experts on here say that the alternative little rubber ring 'seals' are ineffective. So what should I do about controlling oil entering the cylinders down the intake guides: do I omit valve stem seals; do I use the O-rings anyway; other oil control methods?
Don

I've sought such advice recently and opted for a set of "top hat" seals for the intake valves only. Phil will probably be along to explain it all shortly but if you look through my posts you will find some of his great advice there.
How much effort is it to renew the seals while the head is off? If it was me, even if I was sticking with the doughnut type seals, being as they're so cheap and if I didn't know how old they were then I'd replace them anyway.

Don
You can fit the 'O' ring seals but in my honest opinion you will be wasting your time. The only way to control oil from flowing down the inlet valve guide is to fit the 'top hat' seals with the correct grooved valve guides.
You will need to discard the shrouds (if fitted) as was done on later 'A' Series engines.
There is no need to fit seals on the exhaust valve as the exhaust valve stem needs all the lubrication it can get.
Both the 'top hat' seal and valve guide are available from ESM.
https://www.morrisminorspares.com/engin ... e-p1238953
https://www.morrisminorspares.com/engin ... l-p1209547
Phil

an anecdote

Many years ago I replaced an MGB head gasket with similar donut seals. I replaced those with the top hat seal without changing the valve guides. What I did was to clean the top of the guide with acetone (celly thinners) and the inside of the seals with methanol (meths) and then to slide the seal over the guide with a dollop of locktite to act as an adhesive. Left the assembly for a day or two to 'go off' then reassembled the rest as normal.

When I again looked at the head about three years later to replace a leaking exhaust valve, the top hat seals were still tightly in place and doing their job.

There may be a third option??

Yes - I agree you can fit the top hat seals without using the grooved valve guides.
The down side is that you do not know how the seals are coping until you dismantle the head or use other methods to remove the valve spring caps.
Personally I would not take the risk of a top hat seal placement going wrong - brought on by not using the approved grooved valve guide.
You have to consider that a fragmented top seal could block a oil way with disastrous results.

Thank you for your helpful replies. It is pretty much as I expected. I really have to install grooved inlet valve guides and top hat seals if I want to do it properly.
I am trying to avoid replacing the guides because I don't have the reamer and seat cutter that are needed to do the job properly. And I want to get the car going quickly.

Don

I don't think you need a reamer for the cast iron guides, I certainly didn't.

Some sort of drift which locates in the bore is useful (I used an old valve with the head cut off and shorter piece of tube).

Remember the groved ones are set a couple of mm lower than the originals.

The correct size reamer is 9/32".
Not all cast iron valve guides have the same precision internal diameter.
So some do need the reamer running through and some do not.
As regards the height of the valve guide above the valve spring seat - if you have a standard camshaft and rocker gear fitted the height of the valve guide should be no more than 0.594 (15.09mm) above the valve spring seat when top hat seals are fitted. The height can be reduced by 2mm if required.

A late thought.
I 've found that those small "O" seals often broken or missing and then have worried where the missing bits might have gone and so in my last build have not fitted any form of valve oil seal at all. With a good fit between the valve and its guide I've noticed no increase in oil consumption or symptom like smoking on start up or on engine speed-up after a prolonged idle. None of my current engines in motor cycles or garden equipment (or those I've had in the past 60 years) have had oil seals on the valves and seemed none the worse for it.
Regards from MikeN.

Thanks Mike
I was wondering whether it would be a bad move to omit the seals altogether. So now I have an answer based on experience.
Don