CliftonGK1

Pacing is probably the toughest thing to learn for long distance riding. (We'll call 80mi LD, since it's all relative.) When I first started LD riding (200k and up) pacing was my biggest issue. I'd start out like a rocket; OK, a really slow, 16.5mph rocket... and around 90 miles I'd be burned out and slow down to below 14mph just to finish out the last 10 miles of a century. I didn't even make it to 200k until my 3rd attempt! That was when I forced myself to keep a steady 14.5mph pace right from the start, even though I felt that I could go much faster. It's not about fast! It's about far. And I've learned that 14.5mph is my (literally) all-day pace. I can keep that pace up for 17 hours (so far. I haven't tried anything longer yet.)

As for food... If you're getting into LD riding, try and temper your stomach to rely on "normal" food instead of just gels and bars and powders. I did my first double (14h 45m) on Clif Bars and Accel Gels and Accelerade. I swear, by the 10th hour I was so frackin' sick of those things. No matter how many different flavours you pack, there's just no variety in texture and they all taste the same after half a day on the bike. Blech! (Plus, if you're on a really long ride; like 300k or more; you don't know what the next gas station or convenience store will have in stock.)

I still bring a couple of bars and gels as my "emergency reserve", but I prefer to rely on real food instead:
Big ol' bowl of oatmeal with fresh raisins and a banana before the ride. (Or a McD's sausage McMuffin and a hashbrown if I'm picking stuff up along the way. For realz; you can get some insane power from that garbage!)
Sandwiches: Good dry Italian salami and cheddar cheese with lettuce and mustard on Dave's Blues bread. Cut into quarters for easy 'on the go' munching.
Bananas
Nectarines/plums/apricots (in season)

For a solo century I'll bring 1 1/2 sandwiches, 2 bananas, 2 Accel Gels and a couple of pre-measured baggies of Accelerade. This weekend I'm riding an organized ride (Tour de Cure) I paid an entry fee and my team raises a few thousand for them every year, so I plan on getting my money's worth out of it. I will bring my Endurolytes and a couple pre-measures of Accelerade. They'll have fruit, cookies, gels, bars, pretzels, chips, etc. at all the stops.

What you should really look to do for any long rides is keep up a caloric intake of 250 - 300 cal/hr. That's all your body can usefully process, so that's all you need to take in. Anything more, and you're wasting effort. For reference, a Clif Bar and an Accel Gel is about 300 calories.