an n9y is the stock plug for a 1968-71 340. does it have a CLUTCH fan?? sometimes they go bad and constantly slip. the 6 blade pump was initially used on A.C. and H.P. models, in the engine book by a Chrysler engineer "only the lower horsepower required A.C. pump was used in 1974-82 engines".
Yep ditch that factory fan clutch and go with a hyden HD/truck thermo clutch 90% lock up night and day >>> I saw a 20 degree drop between inlet /out let with a good lazer thermometer >>>>>same day/conditions
