I got it figured out. The old seals were worn enough that they were dropping the valves. When I got the new seals in, the valves stayed up long enough to get the spring caps and the nuts on no problem.
Phil Forrest

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1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson