The electronic transducers that sense engine oil pressure, fuel pressure, and manifold pressure are all mounted on a manifold on the left side of the firewall. I ran the wiring to all three, then used some brass air fittings and the compressor to test the oil and fuel pressure sensors. Manifold pressure is easier to test since you can just compare the readout to ambient air pressure.
I used Permatex #2 to seal the sensors, plugs, and fittings as I screwed them into the manifold. The oil pressure sensor is hung off the side of the manifold, since the oil pressure switch (which drives the Hobbs meter and the low oil pressure warning light) is much too big to be placed anywhere else other than cantilevered straight out from the firewall. In fact, I discovered to my chagrin that the oil pressure sensor doesn't quite fit either – the radius is too big by an eighth of an inch – but I have a plan for that…
In classic style, I used this little challenge as an opportunity to buy a new tool. Seen here is a vertical milling table attached my lathe, which turns it into a very small milling machine of sorts:
I cut a piece of 3/16" aluminum bar stock, match drilled it to the transducer manifold, and then bolted/clamped it to the new milling table and milled out some lightening holes:
It's not perfect, but it's not bad for my first real part made using a milling machine. It's quite light, since most of the material in the heavy bar of aluminum has been milled out.
Now the manifold can be spaced out from the firewall, allowing the oil pressure sensor to fit:
…just like this:
I secured all the sensor wiring with tie wraps. Later I'll connect the three wires for the oil pressure switch.
The milling conversion attachment for the lathe wasn't all that expensive, but I have a feeling that it is going to end up costing me a more in the long run. Now that I've successfully made a useful part on a mill – something I never thought I'd be able to do – I'm already having impure thoughts about upgrading to a larger and more capable machine. I wonder if Mary would notice if I put a Bridgeport in the guest bedroom?