Sooting plug

[den912]

My 1970 911 T keeps having plug issues on cylinder 4, the plug soots up and affects the running of the engine(low on power) the car has new PMOs and has been on a rolling road 3 times but after a couple of hundred miles the same thing happens, I’ve tried hotter plugs but again the same cylinder and the plug soots up
The plug in the pic has less than 300 miles, all the other plugs are clean, what could be causing this and what could be done to remedy it

[john walker's workshop]

Perhaps the jetting is on the rich side. What do you have? What plugs? What ignition? Float levels correct?

[den912]

I’ve got a 123 distributor NGK BP 5ES Plugs

[digitaldgp]

Following

[Trackrash]

Most likely float levels or needle valves. With the excuse for gas they sell now you have to be very accurate with your float levels. Even a mm too high and it will cause trouble.

How do your other plugs look? Any mods to the motor and what are the specs on your carbs?

Were you running Zeniths and just changed to PMOs?

[den912]

Plug on cylinder 5 a bit sooty but the others are fine, the motor has been freshly rebuilt and has E cams now fitted, I’ve read on other threads that fitting an “MSD 6AL with booster coil” but can this be retro fitted with a 123 dizzy

[T77911S]

one plug?
how about the plug wire.
if you can swap 2 try that.

cap and rotor been replaced.

do a compression test.
check intake bolts.

you said 4 then 5 ???