This is the SAE paper:
https://www.sae.org/publications/technical-papers/content/780633/
Its very well worth buying, there are a lot of insightful pictures included with the information.
Quote:
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There were many changes implemented to both turbo and NA engines after it was published.
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The only change to the 617a after 1978 was an update to the camshaft profile and hardened face followers in 1981.
The non-turbo 617 received the 617a's pencil glowplugs, updated prechambers and updated camshaft parts in 1981. Mainly to maintain parts commonality, but they got a minor power increase from 79hp to 87hp.
After that, all changes were external; A smaller 0.9:1 (instead of 1.1:1) water pump pulley in 1984 and EGR/ARV/TrapOx for emissions in 1984/85.