I've got a 911, but haven't spent more than 15 minutes with a 914, but I liked it. Here's what I've heard - all came injected - lots converted to carbs - 1.7 up to 73, then 2.0 73 & 74. 1.8 afterwards - 1.8 is weakest. Rust on battery tray pretty common. Heard the term hell hole - what is it - rocker/sill area? Selling the 911 soon. What else to look for?
if Converted to Carbs.. the 1.8 is not bad. It is the fuel injection that is used to on the 1.8 that makes it the least diserable. It is known for blowing up it's airboxes. Convert to carbs and run all day.
the 914 is made of thinner steel than the 911.. so they do tend to bend a bit in the middle. Check the gaps along the trailing edge of the door. They should be even from top to bottom
There are plenty of metal parts for this cars to patch most rust spots. There is also a strengthening kit that can put extra metal into the sills to really stiffen up the car.
I miss mine, but it was an extreme rust bucket, but fun while it lasted
Hell hole is the front right corner of the engine compartment right below the battery tray. Leaky battery = rusty corner and the right suspension trailing arm mounts are there. 
Not easily seen and not an easy fix. Easy check: bring a ~200 pound friend, open/close the right door with the car empty, note how well it works. Put friend in right seat, try it again. If the door operation changes drastically (for better or worse), investigate carefully, preferably from below with a really good flashlight. To compound the possible problems, Porsche saw fit to stick the engine computer there as well. Yeah, put it right under a big ol' lead/acid storage battery. 
The rear windows can leak water, this runs down behind the big upholstered panel (meaning you never see it) and this leads to rust at the very rear of the floor pan. Problem is, that is also the front side of a big 'box' member that goes all the way across the car and if the front side of the 'box' rots away, the car becomes MUCH more flexible.
The FI actually works pretty well and is reasonably trouble free. It is crude, though: I heard it described as 'caveman fuel injection'.
There are rear shift and side shift transmissions. Rear shift is the early cars, the shift linkage goes all the way to the rear of the tranny and there's a fork and rail arrangement which hangs out in space, which then turns the shift input 180 degrees. It adds a lot of places for wear and the resulting shift linkage slop. Side shift eliminates the rear U turn and moves the selector stuff inside the cases, it's much better but the shift mechanism is still less than optimal. I don't recall the exact year they changed, I think it was 1973.
Actually, the 1.7 is the weakest motor. It also has the dubious distinction of being the hardest to hop up; the cases won't allow for the really 'big bore' kits to be used unless extensive machine work is done, the cylinder stud pattern is too small and the valves are undersized as well. The 1.8 is a much better start for a big hop up, bore and stroke can go out to 2500 cc. The 2.0 is famous for cracking heads and they are true Porsche design, meaning $$$ and rather rare. Don't confuse the 914 2.0 with the VW bus 2.0, completely different heads, the bus heads are similar to the 1.8.
I loved how mine handled, even with cheapo tires it turned like it was on rails. I swear it handled better than my X 1/9's and that's saying a lot.
My favorite uncle has owned 4 of them. He finally quit messing with them, and bought another similar car. He remarked that his new car was just like a 914, but it worked.
Yeah. It was a Miata.
Megasquirt for the win!!! Toss that nasty distributor while you're in there!
914s are cool. They have true Porsche feel. They are simple cars and easy to work on. They have an oil slosh problem. Side shifters are not good, and rear shifters are terrible. That said, I raced mine with a rear shifter and only missed shifts occasionally... ;-) The cool thing is to upgrade to 911 brakes and 5-lugs, and it's easy in front but not in back. Solution in back used to be to use early 1970 hubs (cast for both 4- and 5-lug applications) but those were rare and expensive. Rear fender space is limited to about 205s, and that's with rolling the fenders. Oh, they run HOT on track. They really need a front-mounted oil cooler. I tried hard to make a rear-mounted cooler work and, well, it never did. Chassis can be flexible, and rust can fold them in two. Rust inspection is key: jack the car up, pull the wheels, and look up the fender wells into all the corners. Also, the front corners of the engine bay are a major trouble spot. The roof seals leak, are expensive to replace, and will leak again in two years. Just accept it: all targas leak. They have lots of trunk space and the stock seats aren't good. If the tach bounces send it to Hollywood Speedometer for a rebuild. The chassis is very popular for engine swaps but you still need to solve issues of cooling, shifter, rigidity/rust...
Bottom line, the 914 makes a fabulous basis for an all-conquering $150,000 race car. I built a $15,000 914 race car and it was very challenging. As a street car there is a ton of fun to be had with them. I'd really love to see a megasquirt conversion.
David
I'm on my second one. The first was a carbed 2.0 with very tight suspension (i.e. loose fillings now) and it was a hoot. Hell hole is as J-Man described, I spent $1000 having mine rebuilt. At the bottom of the firewall, the rear wall of the seats, is where the battery, heat, rain and the rear suspension all come together. See any good coming of that? The car had Cooper tires that wear like iron which means minimal grip, but at Auto-X it just flew! Throttle steer is fun.
My current one was purchased from the original owner with 57,000 miles on it, dead stock FI 2.0 5 speed. It always slept inside, never out in the winter and only saw rain five times that he could remember. Even with all this purity I had to rebuild the rear deck lid hinges. Not from battery acid, but the metal just "ripped" like a piece of paper. Pelican Parts has ANYTHING you could ever need for a 914 by the way. The restrictive stock muffler got a hole in it so I replaced it with an aftermarket one, not the full blat race one, but the medium tone and it makes a huge difference in perfomance and driving enjoyment.
I love these cars for their sound, looks and fun. People always stop and look because they're different but not intimidating in a scary race car way. The interior offers more room than any other sports car I've had or evensat in, period. My only suggestion would be to find the cleanest rust free example money can buy. The $700 spent to ship one from Utah or Arizona is a small investment compared to the $700 spent on weld wire, Bondo and beer chasing rust.
Go through the GRM archives or buy a the few back issues that cover their 914 project car. Tim did some things that I probably would not have, but he has resources that I don't. The car was Zambizi Green with a tan interior, beautiful car. Tan is not a common interior color.
http://www.914world.com/index.php
If you're ever in the neighborhood.....
Dan
Problems:
Rust
You might have to deal with Automobile Atlanta. I had two friends who worked there. The absolute horror customer service stories they tell me are epic.
A little off topic, but I think it is amazing how these cars have jumpped in price in the last few years. It wasn't that long ago that a reasonably determined highschool student good buy a mostly presentable "driver" 914, now I see them listed for over $10K. I do still see some cheap project cars though. I myself passed up a ratty but driveable 914 while in highschool because the owner wanted $800 and I only wanted to pay $500. Sometimes I wish I had bought that car, even though it was rusty. That was about 15 years ago, so not that long in the big scheme of things.
I forgot about the deck lid hinges. The bushings and bolts will rust together and then one day you try to raise the deck lid, it seems a little stiff then falls over to one side or the other. That goofy spring setup doesn't help.
Automobile Atlanta can be a PITA to deal with but if you catch the 914 Guru (George Hussey) on a good day he can be very helpful. I never figured out exactly what would bring on a good day, must have been a combo of moon phases, lovin' at home, a positive bank balance and maybe other stuff. Pelican was always good to deal with.
I know styling is subjective, when I bought my car it was faded goldish yellow and it wasn't very attractive (I bought it from my brother to help him out of a jam). I stripped the vinyl 'sails' off, welded the molding holes up, filled in the front side marker light holes, added a right side mirror then painted it Guards Red. The car was really nice looking after that, it got compliments everywhere I went.
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