Guys, I am running a 72 455 with stage 1 heads and 9.5 to 1 compression. I have a new 4 row radiator, proper shroud, new water pump, new HD clutch fan. 3.42 gears At cruising speeds and idleing my engine temp is steady around 175-180 but on the highway it will climb up to almost 220. It hasn't gotten any hotter then that yet but I haven't had it out on the hottest days. So what temp is too hot? Prior to changing my exhaust from 2" duals to 3" x pipe and 2 1/2" tails it was much worse . It would shoot right up to 220 or higher at speed. I changed to a 160 t stat prior to the exhaust and that helped some. Do you think I should go back to a 180 stat now that my exhaust is allowing more heat to escape? Jake
I'm having almost this exact problem right now. The exhaust in your case helps diagnose it. The flow limitations affected the engine temp. That kinda indicates that it's a hot cylinder rather than lack of cooling. So... check for lean carb or timing issues first. I checked mine on a dyno and it was dialled in perfectly... still getting this same trouble, so don't take my word for it. Don't take the car over 220 IMO. I'm nervous at 210-220 right now.
I had the same problem as you guys in my `67 a few years ago,it would drive cool but when i hit the highway it would not stay cool,it would climb,it turns out the radiator was`nt cooling the engine at high rpms so i switched to an aluminum radiator(Griffin),never had any cooling issues again.
You could try experimenting with a few more degrees of advance, but you're close enough that it shouldn't be a problem. Verify the vacuum advance is working.
RADIATOR COOLING sounds to be the problem to me. Pull it out and take it down to the RAD shop and have it RODDED out. What they do is pull one cap off and run a rod down each row/tube. You probably have a lot of the clogged up over the years and need to be cleaned out. Mike
