That's right. Cool23 is on to it.
Just check its not fuel precolation.
There is another three bits of trick kit Ford Australia used from 1982 to 1992 on the X-shell Falcons. It like a Fast Eddy Speed Bleeder for brakes, but its for the cooling system.
http://www.fasteddysports.com/?page_id=3&product_id=810
The X-flow Falcon has a purge valve that bleeds air out of the upper radiator hose housing. Just like the Nissan 200/240sx.
Everything from the 170 iron non cross flow to the last 1992 and alloy heads have the same kind of radiator hose thermostat outlet casting (there is a small hose size difference), but on the X-flow it is angled or clocked it around a little. One of the securing bolts has a little air bleed 'petcock' on it, and you bled air out after the engine has cooled from a trip when the engine was coolant was changed.
The removal of air removed ineffective cooling via cavitation, or entrained air.
The second other thing 1982 XE-1992 XF X-flow Falcons did brilliantly was how the X-flow I6 2-bbl engine delt with hot fuel handling by excess fuel bleed back fuel lines.. This was a 1972 on German Pinto engine 1.3/1.6/1.8/2.0 liter and 1983 on wards Ford 5.0 HO 4-bbl GT idea, but it took many years for Ford Australia to adopt it.
the US set up used a Precision Mechanical Fuel Pump Part # M23029 Line on the 4-bbl HO GT 5.0
http://www.oreillyauto.com/site/c/d...ck=Search_C0401_1133682_-1&pt=C0401&ppt=C0025
And v Aussie 3.3/4.1 x-flow return line pump with a huge vapour chamber
Lastly, the Wber ADM 34 carb (and the 4180c 4-bbl as well I think) had an idle stop solenoid to stop running on. Thse three things make a huge difference on a hot Ford I6 or V8.
Those of us lucky enough to have used the base model XD and XE Falcon GL 5.8 125 mph, sub 16 second quarter mile 200 hp performance machine of the Aussie Cleveland V8 missed out on all these advances. I think it missed out on the cooling bleed petcock, , it used the old non bleedback fuel delivery system, a defective heat seaking plastic Thermoquad 9600 4-bbl, and with greatly reduced radiator air flow with the smaller grill inlets, and it sadly missed out on the brilliant 4180c 4-bbl 5.0/5.8 and 370/460 truck fuel system. It often suffered hot fuel handling problems and post operational boiling. When people slapped the more common closed chamber 302C 2V heads on them to boost power via a Boss 351 style 11:1 compression ratio, half the time, they'd diesel and you couldn't turn them off.
A forth trick if it is hot fuel handling problem is this.
MustangGeezer used one on his old log head too