Porsche 928 Workshop Manual page 181

928 Engine/Cylinder Head. Valves
15
CHECKING INSTALLED LENGTH OF VALVE SPRINGS
928s Beginning with 3.81
Valve Springs
Valve springs jets with progressive outside springs on both rides (formerly only one ride) were introduced
beginning with
Engine No. 821 0516 M 28/11 or
821 5503 M 28112 Automatics.
This change made it necessary to have large valve spring bearing surfaces on the cylinder heads.
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New
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Old Version New Version
The new cylinder heads can be installed in pairs on older engines or only on one engine side together with
the old version. The progressive valve springs with accessories must always be used on the new cylinder
heads on both sides.
Old valve springs, discs, stem seals, guides and washers are still availabe.
Printed in Germany . VII, 1983
Checking Installed Length of Valve Springs / 928 S
15.8c