hi there
Have a problem with my '71 S bug
When it rains it is really difficult to start
I cant figure out where the water is getting in.
The dist. cap is dry.
I have a DCNF carby
good job the battery is in good nik cus it takes ages to kick over then for and few seconds sounds like its running on a few cylinders.

any clues

More often than not it's the dissy however maybe there's condensation getting into your leads.

Pop the distributor cap tonight and spray inside it (and outside) with WD40 or similar water repellent.

If it starts next wet morning, you're up for a new cap, if not, move onto the leads.

hth