Bringing this back up because I still haven't found a solution. Things I've done since bringing this up. Installed new radiator with homemade shroud (see image). Installed a high volume pump (130-1270P) with all new hoses. Checked the timing (pulling vacuum), and it's spot on, and double-checked the spark plug wire connections. Replaced all the spark plugs. Fill and bleed using the handy Lisle kit. Checked that all spark plug wires are conducting good.
- Overheats under load - Highway speed (55 MPH), or climbing up a hill (like Kipling from Morrison to Jewell). I cannot make the ride home (40 min. drive) that's a combination of surface streets and 285 without breaching 210*. It will recover if I can cruise at ~1500 RPM or downhill.
- Water is disappearing - Not into the oil or onto the ground...some of it is undoubtedly from overflowing the overflow tank when overheating, but I suspect some is out the tailpipe.
Does the fact that it's overheating under load point to the timing not advancing enough? Or another problem with the HEI distributor? I have not pressure tested the system, would it make sense to do so now? How about a full flush? I'm tempted to swap out the motor (looking at a Jegs crate motor with a Fuel Injection set up), but I don't want to put a new motor in if I'm just going to jeopardize it with cooling problems.
Any other ideas?