Reviving a long-dormant 911 - tips I wish someone had told me

Doing something similar with a 930 that sat in a warehouse since the mid 90s. Agreed on the fuel side of things, the tank on mine had actual rust flakes rolling around inside when I pulled it. I had it dipped and coated rather than trying to swill something through the filler neck, best money I spent on the whole car. The lines were exactly as you describe, one of them split when I flexed it by hand.

Where I'd differ is the brakes. My pedal felt fine but the rears were frozen solid, and I only found out rolling it down the driveway when the fronts did all the work. So I'd pull all four calipers before the first drive, not just trust the pedal. Rebuilt them with new seals and they came back fine.

Also, check the fuel pump with the tank still empty. Mine had seized impeller damage from sitting with old petrol in it, and catching that before the first start saved me a fire risk in the engine bay. Cheap enough part to just swap anyway. Two years in now and it's still throwing little things at me, but you're right about knowing every noise. When something changes, I can ussually tell you which corner it came from.

The point about a short first run is spot on, that thirty second window tells you a lot. Mine was a 944 that sat about the same length of time and I kept a fire extinguisher clipped to the garage wall for that first start, wich turned out to be a smart call because the mechanical fuel pump seal wept petrol onto the block as soon as it got warm. Caught it by smell before it could do anything worse. Also found the heater control valve had gone brittle and dumped coolant on my feet when I first touched it, so have some rags ready for the surprise leaks too.

I'd push back on the compression check being the gate before a first start on these. Mine had sat nearly as long and the numbers came back lumpy on two cylinders, low but not terrible, and everyone said that meant rings stuck from sitting. Turned out to be valve seats gummed up with old varnish, and after some running and a dose of upper cylinder treatment the readings climbed on thier own. If I'd treated those numbers as a verdict I'd have pulled the engine for nothing. Decent numbers don't mean much on a long-sitter, and bad ones can still come right.

Update: sent my tank off for dipping after reading that comment about rust flakes. Glad I did, the inside was worse than the swilling-through job I'd originally planned suggested. One thing though, my compression numbers were slightly uneven on one bank and I blamed the rings. If old varnish on the valve seats can throw those readings off, maybe mine was nothing after all. Might recheck it now the engine's had some running.