Spark plugs 3 and 4 getting sooty black matte during the first 20 mins of idle at parking lot.

[jalexquijano]

Just changed the cap, rotor and Brand new ngk bp6es spark plugs on my 1972 240z. Cranked the car and after 20 minutes of idling spark plugs 3 and 4 are sooty matte black not oily. Is this normal??? how do i get rid of this. My compression test marked 180 psi for all 6 cylinders.  The weird thing is that it only shows up on spark plug 3 which is fed by the front carb and spark plug 4 which is fed by the rear carb. Both of my carbs are 3 screws round top remanufactured by Z therapy in dec 2014. SPark plugs are NGK blue type and distributor is original Hitachi with pertronix ignitor module and ignitor flamethrower coil. Car accelerates and has no problem at high rpms.

[C.A.R.]

The easiest fix is:

 

 

 

DON'T IDLE THE ENGINE FOR 20 MINUTES!!!

[jalexquijano]

Give me a better response.