So having got the guages home I look at them and start wondering OK smarty pants with your mechanical guage theories, how do you hook 'em up to a motor built in the computer age??
Oil pressure is the easiest, just hook a line into a pressure feed some where and run it back to the guage. Images of hot
oil squirting out from under the dash made me think a bit more carefully about this. A braided line with decent fittings is the go.
Fist thing was to find a suitable location to pick up a pressure feed from. You can usually put a T section in with your electrical
oil sender for the ECU but the LS1 doesn't have your usual kinda sender or thread on it. There's a boss on the sump directly above the oil filter that looks more promising. This is a smart design on GM's part, High pressure oil from the filter comes out of the sump and goes through a bolt on U shaped section and gets ducted back into the galeries. The upshot of this is that this thing is designed with plumbing an oil cooler in mind. You can either machine up a plate to bolt on here with a couple of #8 fittings or tap the inlet and outlet holes in the sump directly. GM kindly provided a boss on the U turn plate that looks like it was made to be drilled and tapped 1/8" NPT. I used a 1/8" NPT to #3 adaptor in the hole and then made up a braided teflon line to run from the adaptor to the guage. This stuff takes enormous pressure and is very resistant to mechanical damage. The braid is also covered with a layer of plastic to stop it wearing on things.
Here's the oil pressure line:
