Valve Stem O ring seal

[MajorL]

I need to replace the valve stem o rings. I see that Bull Motif gives a cup seal and EMS a spring type as new items instead of the old type o ring. Which is the best type to fit or should I stick to the old type? Do the new
ones fit on the same way and place as the old type ? Advice much appreciated. Andy

[panky]

I cant remember if there's a groove in the guide to accept the cup type but if there is get the DuPont ones from Mini Sport, they are a little more expensive (only an extra few pounds for a set) but they are the best you can get - as fitted to the last of the Minis.

[bmcecosse]

Only fit to the inlet valve guides....

[Pucketsport]

My 948 does not have o-ring type seals on the valve stems. The original seal was pressed into the spring seat / oil deflector but everyone seems to refer to o-ring as the original ? And I cant seem to find the original type can anyone help?

If I have to go to the O-ring type, does this fit directly beneath the collets in the same recess as the coletts ?
Please see original seal from my 948 below and next to it the O-ring type.[frame][/frame]

[philthehill]

The seal part number you are referring to is Pt No: 2A 9 and they are the original type of valve seal fitted to the 'A' Series.
Details of these valve seals can be found in BMC wksp man sect A.A.16. and are shown in illustration 6713W, page A.A.10, item No: 14.
This type of seal was discontinued and replaced by the 'O' ring seal which fits under the two collets.
The 'O' ring seal is next to useless and should be replaced with the top hat seal on the inlet valve guides only - so in theory you could get away with only fitting qty 4 grooved valve guides but better if all new valve guides are fitted.
The top hat seals are only really suitable for the later type valve guides with top hat seal locating groove - though some do improvise their securing but I would strongly advise against securing any other way but that designed by BMC/BL i.e. the groove.
If you do fit the top hat seals and grooved valve guides you can ditch the shroud/deflector (Pt Nos: 2A346/2A544/2A545)
The guides with groove are slightly longer and whilst they will fit they do stick out into the inlet and exhaust passages slightly more but they can be easily shortened.
Below is a picture of the two guides to compare and the removal and fitting tool. The longer guide (inlet) has been tapered to improve the air flow past it).[frame][/frame]

[Pucketsport]

Thanks very much. I have a dilemma now. I spent $900 having my head overhauled ( lead free and new guides ) . The new guides don't have the groove ..... Any advice ? With new valve guides would it be correct to say there should be minimal oil passing through the inlet valves ?

[philthehill]

Under the circumstances - I would fit the new 'O' rings under the collets (on all 8 valve stems) and be done with it.
Whilst the 'O' rings are not as good as the top hat seals they will suffice and allow you to put the engine back together and get some use out of the car.
A little oil passing down the valve guide will do no harm and will be beneficial especially to the exhaust valves/guides
Phil

[firehor5e]

some have used "super glue"to hold top hat seals i believe.I would change the inlet guides for the grooved type and fit top hats.
900 dollars seems quite expensive for unleaded conversion,Just had my head skimmed and unleaded conversion for £140 and £24 for the guides(fitted them myself before it went to the machine shop).Would it be possible to file a groove into the guides i wonder?

[philthehill]

Whilst some have used glue to hold the top hat seal in place I personally do not recommend using anything other than the grooved valve guides -
http://www.minispares.com/product/Class ... ssic/valve guide.aspx|Back to search
If the top hat seal http://www.minispares.com/product/Class ... ssic/valve seal.aspx|Back to search
becomes loose and is damaged/broken up the rubber and metal spring can get into the oil ways and do untold damage.
If you do want to fit the top hat type valve guide seals you should use the appropriate valve guides.
The shroud (Pt No: 2A554) needs to be dispensed with as it may well foul the top hat seal and was only fitted to keep the oil away from the top of the valve guide.
Whilst you can file a groove in the guide - unless you get it right it could end up as bad as having no groove.
The valve guide will have to be removed to file/cut a groove in it anyway so you may as well fit the grooved valve guides whilst you are at it.
When fitting new valve guides give the valve a light lapping in before re-assembly to check that the valve seat is square to the valve head. If not the valve seat may have to be re-cut relative to the guide.
Phil

[Pucketsport]

Thanks to all for the valuable advice I have received from my Posts. I have one last question relating to this topic. I want to buy new valves and was wondering if the ones that are readily available from Moss/Bullmotif are good quality. They seem really cheap. I have spent a lot of money on new lead-free seats and new guides and when I received the head back from the garage I noticed that there seemed to be a fair amount of free-play between the stem and the guides. I measured the stems and found them to be a little undersized from wear. ( I had originally asked the Engine builder to put new valves in but that's another story).
So back to my original question, are these valves any good ? Made in England ?

[philthehill]

What is the free play?
Have you measured the valve stems against the manufactures standard?
Unless you measure against the manufactures standard the amount of wear/play cannot be determined to satisfaction.
Below are the manufactures standards taken from the BL workshop manual:-
The valve stem to valve guide clearance should be for both inlet and exhaust 0.0015" to 0.0025" (0.04mm to 0.08mm)
The stem dia of the inlet valve is 0.2793" to 0.2798" (7.094mm to 7.11mm).
The stem dia of the exhaust valve is 0.2788" to 0.2793" (7.081mm to 7.094mm).
Additional information:- Inside diameter of the valve guide (inlet and exhaust) is 0.2813" to 0.2818" ( 7.1450mm to 7.1577mm).
Until that play/wear has been determined I would not consider purchasing new valves.
I would suggest that the inlet/exhaust valves supplied by MOSS, ESM and Bullmotif are of a sufficient quality to be adequate for your needs.
Phil

[Pucketsport]

Thanks very much Phil. A mechanic has suggested I measure the clearance with a dial gauge with the valve in the guide. I agree that I will only change them if out of spec.

[philthehill]

There is little point (but possibly nice to know) in using a dial gauge to measure the valve stem movement in the guide because unless you are prepared to buy sufficient new valve guides to enable you to be selective in their fit to the valve stems you are limited to measuring the wear on the valve stems especially as you say that new valve guides have been fitted.
Therefore you will only need a micrometer to measure the valve stems.
When measuring the diameter of the valve stems - initially measure above the area of valve in the guide movement (just below the collet groove) and then measure several times up and down the wear path and at various degrees around the stem as the stems do not always wear concentric.
Phil