318 popping in left bank header under load. Look at my plugs

Bone stock low compression 79 318. Cheap headers edelbrock streetmaster intake and 625 street demon.
Started popping badly on left bank. At first I thought it was just an exhaust leak so I fixed the leaking header gasket.
I pulled a couple plugs and the electrode has large amounts of buildup on the side of the electrode. This looks weird and Im thinking this is something ignition timing related and maybe lean but I really don't know.
The ignition timing is set at 14 degrees btdc. No pinging or hard starting.

plug1.jpg

plug2.jpg

plug3.jpg

plug4.jpg

plug5.jpg