HELP! Engine stalls and rough idle

[ernest.irw]

Been tinkering my old 1975 series 3 SWB 2,25L-4cyl petrol (3 bearings). I recently changed my old distributor to Britpart electronic red cap distributor (model ETC5835ERED). I set the ignition timing at TDC because I am using 90-92 octane fuel. Crank the engine until no.1 spark plug positioned at top dead center and install the new distributor with the rotor pointed at no.1 spark plug cable. I am using weber carburetor my settings are: air mixture to 2x turn and the idle speed 1 1/2 turn. It was running fine for a month the acceleration is good but recently I took the rover for a drive at about 80 kph (50 mph) slow down at stop sign and the engine stalls. I could restart the engine easily but after I stopped at a junction, it stalls again. After I got home the engine idles rough and suddenly it idles faster than it should (sudden increase in rpm without touching the accelerator pedal) and it stalls again after a while. I’ve tried increasing the idle speed, but similar result. I’ve checked the spark plug one by one and it was wet with fuel because I set the carb too rich. I reset the carburetor, tuned down the idle speed, clean the spark plug, clean the fuel filter, air filter, spray the carb with carb cleaner, advance the ignition timing and start it again. But all the efforts ended up similar result.

Could it be a bad electronic distributor? A vacuum leak? Failing head gasket? Or more serious engine problem?

These are the photos

[ernest.irw]

It turns out to be multiple causes
1. Vacuum hose from brake booster to engine manifold (small crack)
2. Vacuum hose from distributor to carburetor (expanded and kinking near the fittings)
3. Ignition coil (coil getting very hot after the engine reach higher temperature)

I replaced those parts and now the engine performs very well.