Last night was a revelation.To paraphrase Buckminister Fuller:
If the theory does not hold up in practice, check your premises.
So I checked the compression again. #1 50 psi, #2 120, #3 120, #4 50
How come..? Think the oil seeped out as V40 was in the sun..?
I'm going to pull the plug. (as well as ...

Rev'd but no speed is what my kid said happened on way home.
4300 or so rpm, no road speed. Used Volvo cam retainer to set
cam pulleys. Crank pulley marks line up perfectly. Took it apart
twice to make sure. Crankshaft pulley between the 2 marks.
Compression: #1 180 psi, #2 180, #3 165, #4 180 ...

Backstory: Last time, Nov 2017, it ran, it rev'd but no speed. Once home would not start.
Local Volvo guy said compression OK, but timing belt covereed in oil + slipped a few teeth
on intake cam gear. Cleaned up oil, installed n t, both cam seals (using retainer)
crankshaft seal, +waterpump. Started ...