With all engine parts now finished except for the piston rings, it would make sense to start on them next. Piston rings are really boring, and with so many ahead of me it's hard to get moving in that direction. After lots of procrastination, work is continuing instead with the more interesting running accessories like the radiator, ignition module, and fuel tank. They'll eventually be needed to run the engine, and finishing them before the rings will remove any temptation to jury rig a first-start that I might regret.
The radiator was tackled first. The holy grail for a model V-8 is getting one to idle indefinitely without overheating. Subjective results from my last two engines suggest that more cooling capacity may be available from a simple hollow core compared with one having the same outside dimensions but made up of finned cooling tubes. This may be nonintuitive, but there are some reasons that support it.
Jerry Howell's V-4 radiator is a well thought-out example of a finned cooling tube radiator, but if it instead had a plain hollow core it would hold nearly 3X more coolant. Cooling fins add realism, but in most models without an electric fan forcing air through them, the fins are more cosmetic than one might think. Cooling tube construction is typically done with brass because of its solder-ability, but aluminum has 4X better thermal conductivity.
Construction began with the radiator core and was greatly simplified by starting with an extruded rectangular aluminum workpiece. The piece of 6063 architectural material that I had on hand has slightly better thermal properties than 6061, but it's soft and more difficult to machine. An array of grooves milled on both sides of the core adds the look of fins and even increases the core's surface area for better heat transfer.
A full-size 289 with a three core radiator has a coolant capacity of 14.7 quarts with of 25% of the coolant inside the radiator at any time. If scaled by volume and assuming all else equal (it probably isn't) the goal for the 1/3 scale model's total coolant capacity would be .54 quarts. The engine's actual coolant capacity works out to be only .15 quart, but a 1/3 scale radiator with a hollow core will add another .85 quart giving a one quart system total.
The upper and lower tanks were machined from 6061 billet with features similar to those on the drawn tanks of a typical 60's era radiator. They'll eventually be JB Welded to the core, but in the meantime they were bead blasted to provide bite to the epoxy and paint. - Terry