The distributor was pointed at #1 wire? If so there should have been some valve
lash at that point so both valves would be TIGHTLY closed (compression stroke).
If there was no lash at that point you would have been between exhaust and intake
strokes where you do NOT want it firing/backfiring!
The instructions in the Green Volvo manual are kinda screwy in that they have you set
it up in firing position for #4 (#6 on the B30) for reasons unclear to most of us.
Anyway whichever you use, 1, 4, or 6, the IMPORTANT thing is that this is the compression
stroke so both valves need to be tightly closed, therefore SOME clearance on both
valves for that cylinder. If you don't have clearance either change the wires two positions
or straight across, or turn the crank 360 degrees (one full turn) and try again.
By the way this happens to EVERYBODY because of the way the manual is written.
I've spent hours on overseas phone calls trying to convince hard-headed (would you
believe Dutch?) relatives. Finally called back and said, "Yep, you were right!"
--
George Downs Bartlesville, Oklahoma