Modified Valve Spring Cap and Improved Valve Stem Seal

Although gasket sets still seem to include eight tiny rubber ring oil seals for the valve stems, it is generally accepted now that they are not the best solution to stopping engine oil being drawn into the combustion chambers via the valve guides.

A later style of seal has been developed that is more like a "hat" on the top of the valve guide. It is less prone to hardening than the old type and provides a better seal on the valve stem. P1010005webIt is also more effective at preventing the seepage of oil into the combustion chambers during idle periods and visible as a puff of blue smoke on start up. Furthermore, it is also common practice now only to fit seals to the inlet valves because it is the vacuum on the induction stroke that is most likely to suck the oil in. Oil penetration down the exhaust valves is negligible and, of course, some is needed for lubrication. The picture shows the newer type of oil seal in place on the inlet valve guides. The seals have an internal rib that matches a groove on newer guides so that it is held in place.

During MGB production, the circular cap on the dual valve springs was also changed and the funnel-shaped oil deflector that sits inside the springs was also deleted. It is possible that Magnette engines that have been professionally rebuilt will have been modified accordingly, so if your engine does not have the deflectors it is not necessarily a problem. Their deletion may have been based on cost-saving by discontinuing a part that added little benefit. The intention was that as the valve was compressed, the deflector would reduce oil splash from the springs onto the valve stems. P1010004webThe second photo shows the newer style of valve cap (left) next to the original type (right) together with the deleted deflector that goes with it. The newer cap has a different profile and the central raised area has a slightly larger diameter to locate the inner spring because it no longer has the deflector to do the job. It follows that the deflector cannot be fitted to the newer cap.

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