The inductive tach recommended by Eccentric arrived. Mine's a slightly different model but still very easy to set up for a 6 cylinder engine (or any other number of cylinders). From its lope I was sure I had the engine idling at 800-900 rpm, but the tach kept telling me the real number was nearly twice that. I thought a setup issue or electrical noise was causing too-high readings, but after a lot of troubleshooting I was finally convinced the tach was working as it should.
With my confidence in the engine growing, the carburetor was retuned for a top end of 5k rpm even though full throttle was 7k. These higher speeds required the fuel pump to be bumped up in order to maintain a constant level of fuel in the bowl. Still, the air bleed adjustment didn't seem to have much effect.
Carburetor tuning doesn't seem to be affected by the air cleaner. Suction through the intake snout is noticeable though, and the engine will immediately stall when it's covered. It'll be used as a choke during cool weather starting.
With the rocker cover and air cleaner removed, I took a number of IR photos over various surfaces of the engine during and after a two minute run. The first two photos are overviews of both sides of the engine as viewed from its rear taken at the end of the run. The siamese'd intake manifold eventually rises to the same temperature as the exhaust manifold which is some 250F.
The third photo is a closeup of the intake and exhaust manifold surfaces taken well into the run. The intake runners which are cooled by fuel while the engine is running are some 20F cooler than the exhaust runners. All three photos show the carburetor as the coolest part of the engine - most likely a result of the cooling provided by the recirculating fuel. The fourth photo shows the effect of manifold heat on the carburetor about midway through the run. Although the temperature of the carburetor's base has risen, the important area around the Venturi remains cool to help keep tuning consistent.
The fifth photo is a closeup view of the top surfaces of the head taken near the end of the run. It's 177F temperature is representative of the hotspots between the rocker assemblies and above the combustion chambers along the entire length of the head. These hotspots are uniform across the width of the head despite the fact that one of the head's longitudinal coolant passages was blocked during construction and is non-functional.
The sixth photo shows the temperature gradient across the front face of the radiator at some 1-1/2 minutes into the run. There's a 10F gradient from top to bottom with the hottest area at the top of the radiator being some 140F. This temperature is 30F-40F cooler than the hotspots in the head. This gradient all but disappears during a longer run when the face of the radiator settles out to 135F.
The last photo is a view of the port side of the engine midway into the run. With the side of the head at 155F, the crankcase is a fairly uniform 143F with the oil pan some 20F cooler. All in all, the photos show a pretty effective cooling system that I wasn't expecting and head temperatures considerably lower than I expected.
This build has been so much fun that I'm having trouble ending it. I never considered designing a pcv valve, but I did press out a brass 2-56 wing nut for the air cleaner cover which I then nickel plated. That nut is similar to the ones used on some Ford engines from the same period. - Terry