compatibilty of square four valve guide shrouds

[ben.mitchell]

The 1955 MkII square four used shrouds on the valve guides to reduce oil splash onto the valve stems which could then otherwise run down the valve and either burn onto the stem or burn up in the combustion chamber...not good either way! Has anyone ever fitted said shrouds to a MkI engine, we already have the Waller modification of a knife edge on top of the rocker arm plus we have valves with the lower part waisted but I am keen to further reduce the oil flow down the stems so want to fit the shrouds but I don't want parts colliding with each other unexpectedly. I do realise that I have to use a slightly greater internal diameter inner valve spring to accommodate the shroud, but has anyone ever actually done this conversion to a MkI?
Ben

[ben.mitchell]

I have now answered my own question as nobody else appeared to be able to so do. It is possible to fit the late top collar and stepped collets to a MkI but I am not going to do it right now instead I am just using the later valve guides with a chamfered top designed to take the oil away from the valve stem. In any case I would mention that the boss height of the valve guide is critical to the type of top collar otherwise the collet hits the top of the guide at full valve lift...and this breaks the rocker! It appears that a 12.2mm boss is the highest you should go for but be wary with some MkI heads which had an extra 1.3mm step to lift the guide boss even higher.
Ben

[simon.holyfield]

Did you consider some sort of stem seal, Ben?

[david.anderson]

Ben
do you have the dimensions for the shrouds as I would like to make some. It would be good if you could post dimensions and how they fit thanks.
I have looked briefly at fitting positive seals to my Mk2. I know the head runs hot so I was thinking about some teflon seals as teflon should take the heat. Only problem is there seems to be mixed feelings on the use of teflon seals as it appears many consider they starve the guide of oil which would be worse than our current over oiling problem. I have also looked at umbrella type seals which are available in viton. Viton may take the heat in our 4s but I have been unable to find a suitable viton umbrella seal that will fit inside the valve springs. As such the original steel shrouds may be the way to go.
My mk2 was fitted with new valves and guides and 1000 miles later I was amazed at the carbon build up on the pistons due to oil down the guides. My rockers and guides are knife edged but more is obviously needed.
David