Triumph Repair: Odd wet plug, point gap, distributor cam

Question
I have a 1959 TR3 with SU H6 carbs. Car starts fine but will gas soak one plug and one plug only. The odd thing is that plug is getting strong blue spark. All ignition parts are new and adjusted properly, valves are set and the engine is timed correctly. All other plugs have great color. SU's are a bit worn out and may be the culprit. Thx for any help.

Answer
Hi David,
A carb on a TR-3 can't pick just one cylinder to wet a plug on. So you need to look else-where for the problem.

First thing you need to do is run a compression test. Throttle open and at least 4 or 5 revolutions on each cylinder test.

Also you need to test the plug by switching it to another cylinder to see if the wetting stays on that cylinder. If it has the old wire type plug wires and has those Lucas resistor wire ends try switching them to another cylinder also. If resistor wire has been installed on the car test the resistance of each wire with an ohm meter. Check the point gap on each lobe of the distributor cam.

Also a strong blue spark is normally a good spark but even a strong blue spark out in the air can be at fault when under compression. If the compression test shows good and the switching of the plugs makes the wetting still stay on the same cylinder, you need to locate a shop with a scope to look at the primary and secondary pattern to locate the problem.
Let me know,
Howard