Built a 512 out of a 400 for a 77 dodge 4x4 truck. Mild engine 10 to 1 hand ported 452 heads, .520 lift 220 duration hydraulic roller camshaft. FiTech injection on a single plane intake. Engine ran good on the dyno 500HP @ 5,250 rpm and 540 ft. lbs 4,400 rpm exhaust temps were 1,300 degrees. Put in the truck and it agaibn runs really good, but it will slowly keep building heat until it gets to 250 degrees will do that just cruising in just a few miles.


So, I did the following I installed a new 4 core aluminum radiator, high flow water pump and water pump housing, tried a 160 thermostat and then just took out the thermostat. twin 1,200cfm cooling fans, and a new clutch for the stock fan. I even took the engine back out took it all apart and could not find anything wrong. I re-flushed the water jackets, and drilled extra cooling holes in the head gaskets. Honed a little more clearance in the cylinder walls, took some ignition and camshaft timing out of it. It did make it some better, but still in about 6 miles the temp slowly just keeps creeping up to 250 degrees. I have never in my life had an engine ack like this.

With a heat gun it shows a 20 degree drop in temp across the radiator, is there a rule of thumb for how much temp a radiator should drop?

Any other ideas? I have the timing down to 6 degrees at idle and 32 degrees total. It does have a vacuum advance and it does work replaced it and rebuilt the distributor. It does not spark knock that I can hear until it gets really warm and then just a little . Just looking at the FiTech controller the O2 says 14 to 14.5 air fuel ratio on cruise.