By "Z80" I'm assuming that you mean the Zenoah GT-80? If so, I drilled & tapped mine at the base of one of the cylinder, on the 'flange' of the crankcase..... some disassembly required. I ended up using one of the B&B 90-degree smoke taps.

I did the above while awaiting a reply from Horizon on the best place to tape the engine. After I did the above I finally got a reply. They suggested putting a "T" fitting into the pressure line that drives the diaphragm pump on the carb.... case is already tapped!

I tried both ways (plugging the "new" tap when trying the "T" fitting method).... both ways did indeed work. Perhaps it was just a desire to be proven that I didn't do aa bad thing, but it seemed to me that the tap off the case worked a little better than the "T" method..... but the "T" method is a whole lot easier.

I'd suggest using the "T" method and giving it a try.... if you're happy with the performance, great. If not, you can always tap the case later.

BJH