I have a 68 400 HO, 4-speed close ratio, 4:33 rear end that runs hot at higher rpms. It has the big radiator with new, correct cap, fan shoud, operational clucth fan(correct ddaimeter), and what looks like a new water pump. It'll idle all day and run normal temps. Turns high rpms at highway speeds and the temp slowly creeps to 210-215, so I push in the clutch and let it idle as I coast and the temp goes down. Last time I had to stop and idle to wait for contruction "follow-me" truck and it cooled way down even after 15 minutes of idling. Once back in motion, gets hot. I've tried every where from 180-195 thermostats to no thermostat. (just to troubleshoot) I've been told just to live with it cuz the 400 has no water jacket between the cylinders, thus gets hot at higher rpms. Dont have a tach, but I'm pretty sure with the ratios in the tranny and rear end, they are way up there at 60 mph. Also, once it's hot like that, wont crank over till it cools down some. It has never overheated since I dont let it. Dont travel more thatn 15-20 miles when I drive it. Any suggestions ya'll?
