When the US market changed over to Unleaded low octane fuel, British Leyland
was faced with longevity issues with the venerable B series engine.
To reduce the possibility of valve recession the valve seats of US bound
engines were induction hardened. This was a very expensive process and it
is very unlikely that the factory would have chosen this direction if there
was no wearing issue. The original exhaust valves were retained, as it was
determined that the material was suitable for the more critical application.
After spending many years trying to source good usable B-Series and A-Series
heads for customers. I can state that both designs are subject to a high
degree of exhaust seat wear. The combination of high spring tension, hard
use and iffy fuel quality and mixture tend to aggravate this wear.
Each Persons Mileage May Vary (EPMMV) but I go on record stating that
exhaust valve seat longevity is a limiting factor in A Series and B Series
engines. Correctly installed hardened valve seats do improve this area.
Obviously I would not suggest pulling down a running engine to install them.
It's pretty obvious when they are needed, as the valve lash goes out on a
weekly basis.
Come to think of it, the argument seems rather academic. I don't think I
have seen an original pre-75 head lately that had any exhaust valve seat
left to quibble about.
Kelvin Dodd
> and is still smooth, lusty and pulls hard (sound like a girlfriend I
> had).
Barrie, thank you for this image. : )
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