help 2000 sl

i changed my sparkplugs this weekend and since i seem to still have a intermintent put in the sound of thecar as well as it seems to be running hot,i checked the previous plugs were set at .040 and the wires were 7mm replaced with ac plugs and the stores brand wires but when i get home from work today and opened the hood it was rather warm. i stopped for dinner about 45 minuets and when i started the car it went straight to 1/4 warm and gets to almost 1/2 and the fan kicks on i was told if the wires were the wrong size it can run hot, but the wires are the same size but seem awfully cheap any suggestions would be appreciated