Is it safe to try to start up my project with what I assume are original fuel lines? I won’t be driving anywhere, just want to see if it will turn over with the work I’ve done so far.

You'll be fine.

The way fires start are arcing which is not something that should actively be happening on any vehicle that is running and fuel leaking onto hot engine parts. That is the start of the fires. It's usually been leaking for a mile or so.

Depends on how bad they are. Bend and flex them looking for cracks

Get a fire extinguisher and watch for any leaks in the engine bay. We started a low mile car that mostly sat and a fuel injector leaked after ten minutes of running.
Fuel dripping on the exhaust is bad.

^ This.

I've been worried about this at various times after reading 914 fire threads—which are always awful to read—and looking at the original plastic "hard" lines from the front of the car to the engine bay, now 47 years old and in use for 250,000 miles but garaged for most of its life. I've asked two very good mechanics who know Porsches, and 914s, to inspect the lines and both said the same thing: Don't change them, not even to the nice stainless lines available, because they're still clear, soft, and pliable—but we did cut the end off of one of them in the engine bay because its last inches were hard and crusty.

All other fuel lines were replaced during a six conversion, using the pretty cloth-covered file lines—which started leaking (a lot) in several places after just a few years. It was bad, too, as I could see the leaks with the car idling in my driveway (the smell was the first giveaway). Apparently, the supplier puts pretty cloth over sub-par rubber lines. Everything has since been replaced by CIS hose, which isn't as nice looking, but I'm told should last for a long, long time. I know what I'd rather have...

Get fuel pressure in the lines and inspect for leaks. Crank the engine and continue inspecting for leaks. If you have a leak, it shouldn't be too hard to find. If so, shut it down immediately and make the repair.

It is interesting that the mechanics said not to replace the lines with stainless. We replaced the lines on three 914’s as per our mechanics guidance.

IMO stainless helps me sleep better

I hear you, and am curious to watch this thread for others' viewpoints—although it's always a trick to balance forum wisdom vs that of experienced mechanics.

Man, I am so paranoid about fire, that I went overboard.
Changed the plastic lines for ss, actually the plastic lines looked like they were in pretty good shape.

Then when I added my mega-squirt injection system, I went to steel braid an-6 lines and connectors.

When I put fuel in the tank, and powered up the fuel pump, I had leaks all over the place, mostly from not tightening up stuff enough.

I had a 68 bug catch fire on me, when the brass fitting came out of the carb, thankfully I had a fire extinguisher, and did not torch the whole car.

As soon as I complete the injection install, I am going to get a Blaze Cut system, and put in the engine deck lid, in addition to the one that I have in the car.

You cannot be too careful, cuz by the time you notice it, it's probably to late.

My mechanic also told me not to replace them - Tony at EQ who's been working on 914s since he was a kid in the old country. The lines are still soft & pliable. The car is a "73.

Understood, more data is good.

For context, we have two mechanics, one did his apprenticeship on 914’s at the Seattle dealer in the early 70’s... he told me that apprentices were not allowed to touch the 356’s or 911’s and were forced to work on the 914’s, which is lucky for me. Our other mechanic is Porsche Gold Certified, and did his apprenticeship in Germany in the early 80’s and then worked at RUF in NY for many years until coming to Seattle. He knows 914’s but did his apprenticeship on early 928’s.

Both mechanics agreed that the first thing to fix are the gas lines. That said, statistically the other mechanics might be right in that it probably wont be an issue, but I doubt any mechanic would disagree that SS is safer than plastic.

IMO it was cheap insurance and peace of mind...

btw. after the latest street fire posted we are buying fire extinguishers, for the same peace if mind.

Food for thought. A mechanic may or may not have your interests at the top of the list of things to advise on.

America has become a litigious socieity. Any number of lawyers would love to own your mechanics bussiness because he advised you to do something that then could be connected to a fire or loss of life.

Thus, keep the OEM lines is a very safe response from his perspective. If they do leak and you get hurt, it is not his problem. Your only recourse is to take it up with the OEM.

Plastic lines running though the passenger compartment would have little chance of meeting modern FMVSS 301 fuel system integrity testing. Obviously, a 1970's era 914 never had to meet this standard and the OEM will only be held to the standard in place at the time of vehicle manufacture.

Personally, for my vehicle, I'll go to stainless steel lines rather than depend on 40+year old plastic lines to have retained their original integrity regardless of what a professional mechanic may have to say given that he has a different self interest than I do.

Stainless 100% of the time, just make sure it is supported properly and does not flex you will be fine. And while your at it replace all the rubber lines.

Chris has all the parts you need at Tangerine Racing even sells a package deal to make it very easy to bring your car up to new stuff, and new rubber 30R9 hose, which is about as good as it gets today.