Valve seals

[Tom and Maria]

Just finished rebuilding the head on my new engine. I have top hat type seals with little springs over the guides, and also small O rings under the cotters. The question is - some of the o rings have got slightly caught on the sprng caps and don't sit true, being caut on the valve stem. Are they really needed if top hats in place? Do I need to remove the springs and try again?

Thanks,

Tom

[philthehill]

You should use one or the other not both together.
If you use the TOP HAT seals you should really use the later valve guides which have a retaining grove for the seal. You may have to shorten those valve guides to suit your head.

[Tom and Maria]

Great, that is what I wanted to hear. Confusingly the head had both when I took it apart.

I think i'll remove the o rings. Athoug, is there any harm in using both?

The valve guides have the groove so all fine there.

Tom

[philthehill]

There is a difference in the valve collet/spring cap/recess on later valves and your cylinder head arrangement may not be suitable for fitting the small 'O' ring. As your valve guides have the correct seal/location grove for the guide I would ditch the 'O' rings and just fit the TOP HAT seals.
There is a difference of opinion as to whether it is wise to fit TOP HAT seals to both inlet and exhaust valve guides. All the later BMC/BL heads that I have worked on have been fitted with TOP HAT seals on both inlet and exhaust valve guides and I always do the same. No doubt someone will advise otherwise!

[bmcecosse]

Certainly DO NOT use both O rings and top hats. For Comp use the top hats are never fitted to the exhaust guides - to ensure adequate lube for the hot exhaust valve. I dare say it doesn't matter for road use - although I never fit them to the exhausts.

[Tom and Maria]

Strange, as both were fitted when I removed it, but Will go with just the top hats.

Thanks as always,

Tom