no clue what is wrong with it...there is no place for an allen key to tighten, just a bolt. And the bolt only spins, it doesnt tighten or loosen. anyone got any ideas?

https://youtube.com/watch?v=fZfPW-LF3fk

that's because those are schitty cottered cranks.
move out of the 1970s.

Look here for some information:

https://www.sheldonbrown.com/cotters.html

Good luck.

ok, so i got the left crank off...if i buy a new crank set would they work with this old BB?

Nope, I have an old crankset if you want it, its cottered, I could shoot you the cranks/chainrings/bottom bracket assembly and cotters if you wanted. Ultimately, you'll want to replace the cranks and bottom bracket assembly though.

no. you need a new BB too. Get the one that is suggested for the cranks you are going to buy.

No. Unless by new, you mean new cottered crankset.

Toss that garbage and upgrade to a modern bb and crank. Assuming the rest of hte bike is worthy of it.

If you change to a cotterless crank you might find a few other problems, such as the bottom bracket on that Peugeot (??) has French threading. Then your options are pretty limited and often expensive. By the way, is it a Peugeot?

Personally I LOVE cottered cranks and have a number of pairs. And while that crankset you have isn't the best ever, if the chainring is round and true and the teeth aren't worn, I'd get new cotter pins for $4 and enjoy the ride. Email a store like Harris and buy a set of French 9mm (again I'm assuming it's a Peugeot) cotter pins. Here is a link:

https://harriscyclery.net/itemdetails.cfm?ID=1585

Like the page says, it's a good idea to replace both at once. And it might also be a good idea to repack your bottom bracket bearings at the same time as it probably hasn't been done since that bike left the factory 35 years ago. Here's an excellent tutorial on how to do that:

https://www.bikeforums.net/singlespeed-fixed-gear/208402-maintain-sexy-not-so-sexy-track-bb.html

You can replace just the spindle if the cups are french (and not worn out).

True. Fair point.

i've had a crank problem for years. just can't quit that sh*t. second i get drunk i'm outside the bar calling my guy. super addictive stuff, crank is.