I've got a sb 416, new everything, re-cored, wider than stock, 3 core 26" radiator; running a factory shroud; new thermostatic fan clutch which I tested using the "3/4 tape test",- the fan seems to be turning fine. the fan blades are seting about 1 3/4 inch away from the radiator. there is a cleared, fins streightened, condensor and a new trans cooler in front of the radiator. new, if I remember correctly, 180# thermostat which I drilled two small holes to allow water flow. Theromostat is opening and closing. running a 50/50 mix with temp-cooler poured in. Engine is timed at about 35/36 degrees all in at about 3000 rpm.
The car has a factory temp gauge, which seems to be reasonably accurate. The problem is when I get the car crusing after about 5-6 miles the temp gauge is midway between hot and cold. Then creeps up a little more, just past midway...stays there then I get it home... idleing it begins to creep up toward hot...I shut it off. I can feel the water at a fast-boil when I feel the (hard) upper radiator hose. Header temps will vary between 400 and 1000+ (at #6, previously just after break-in #4 and #6 would be starting to glow! now they are down to 6-700)
Could there be a blocked water passage? The engine was nasty in a barn for a while when I got it. The machine shop, (who's attention to detail I seriously question) cleaned it and bored it as well as rebuilt the heads. The engine builder has no clue. I have had the car running about a year, during which time I have maybe put 40 miles on it due to hot header temps and now overheating worries. Any suggestions are welcome! Please help.
