This photo shows the four exhaust riser pipes, each with a carefully-located and potentially very expensive hole drilled in it. Each one is 3.5" inches from the mounting flange, and oriented in a certain way that I determined after some tedious measurement and trial fitting:
Into each hole goes an exhaust gas temperature (EGT) probe, which is a clamp-on thermocouple that looks like this. I shortened the band clamps on each one to remove extra material I didn't need – these must be sized to fit some kind of monster exhaust pipes. (original version on the right, shortened version on the left)
The EGT probes clamp on to the exhaust pipes like so. I was skeptical that this would provide an adequately tight seal, but they are quite a tight fit into the reamed holes, and I don't think any exhaust blow-by will get past them.
Close-up detail of the safety wire on the clamps. They want you to tighten these to a surprisingly high torque – well beyond what you can do with just a screwdriver – and you definitely don't want them loosening up.
Exhaust reinstalled on engine, complete with temperature probes:
Meanwhile, another set of thermocouples is threaded into the underside of each cylinder, to allow the pilot to monitor cylinder head temperature (CHT). Here you can make out the CHT probes for cylinders 1 and 3:
Here are the CHT probes on the opposite side, for cylinders 2 and 4. (Pay no attention to the state of the mixture bellcrank in this photo, I finished re-hooking it up after I took this)
EGT and CHT probes installed on the starboard side, but not wired yet:
From this angle you can see why measuring the locations for the EGT probes was tedious… you have to make sure the sticking-out portion of each probe is tucked in enough that it doesn't get close to the cowl, but is pointed outboard enough to ensure that it doesn't interfere with anything else on the engine:
Probe wires in disarray on the port side of the engine. In time, I will bundle up all the thermocouple wires and extend them aft to the firewall. But before I can do that, I need to install the magneto and associated plug wiring. One thing at a time.
