Running too Lean?

[drolston]

The engine is 284" with three 97's and a mild cam (Schneider 248f). Runs great except for overheating in traffic and at Interstate speeds. At my wits end on the overheating; a long story that I will not repeat here.

However, my wits keep nagging me that the plugs just do not get to that toasty brown that I am used to seeing on a well tuned flathead. The plug in the picture was pulled after a 250 mile drive, mostly at 60 - 65 mph and about 2700 rpm. White as a ghost. The plugs are new NGK B6HS; longer (7/16") reach for the Offy heads, and a little on the hot side. I have heard on this board that you can not "read" the plugs for rich or lean, because of modern gas, but that plug just does not look right to me.

All three 97s are jetted at .045, which is stock. I am thinking of taking the center/primary carb out to .048 jets. What does the board think? Do I need to re-jet the secondaries as well? Any chance that running too lean is contributing to the overheating, particularly at speed?