Hello Edmund,
Your radiator work of the Jerry Howell radiator for your ETW Sea Lion engine shows excellent workmanship and looks great.
It so happened that I myself am in the process of building two ETW Sea Lions. Besides that, it seems that the two of us share quite a few similarities:
I am of your age.
I have been working on the Sea Lions for now 9 years and time tells me to finish them.
I am married and my wife encourages me to spend time working on the engines as well (I suspect for her own peace and quiet).
With that, I guess we are sharing a seat in the same boat.
I also discovered the Jerry Howell radiator design a while ago and decided to shamelessly copy the idea and implement it with some changes in my own build. The changes I made resulted in a continuous single pass heat exchanger with a total length of 24 inches by effectively looping the coolant back and forth passing only once through all the 6 finned 1/2 inch square tubes. The bore of the tubes is ~ 3/16 (5.0 MM) wall thickness is 1/16 (1.5 MM) The finned tubes in my case are aluminum for better heat transfer using O-rings at the ends for sealing. Top and bottom header is brass. The radiator inlet and outlet is equipped with 1/8" thermocouple to find out the cooling effectiveness. The assembly is put together using Allen head screws and is easily disassembled if needed. No soldering or epoxy glue.
I put a few pictures in below showing the current state of affairs in the build of my engines. I still have quite a bit of work to do on the engine internals since in my style of working I am working kind of backwards, for instance getting the ignition working before tackling the engine guts. For the ignition, I am using the Jerry Howell TIM 6 with a Hall effect sensor. Rigged up the distributor and the four spark plugs for driving with a drill and fired it up. All worked well with decent sparks and no Hall sensor failure while spinning for 5 to 6 minutes but we will see how it goes when the spark plugs fire under compression.
Also copied Jerry Howell's idea of the oil pressure adjustment. Added a small oil sump under the original ETW sump that hides the pressure regulator and also has a 1/8" temperature sensor for measuring the oil temperature. Besides pressure lubing the crankshaft, I also pressure lubricate the 3 camshaft bearings and the valve rockers bushings via the 3/16" hollow 1/16" bored rocker shaft.
Here are some pictures. Apology for the low quality - they were take with an I-Phone. My digital camera battery gave up on me.
Peter J.