Peyton Almond

So I recently bought this 1986 Civic from one of my neighbors and it took a little bit to actually get it to turn over. It wasn't locked or anything, the ignition switch was just bad.

Anyway, I've done the Seafoam treatment, new oil and filter, wipers,and everything is great and it runs perfectly fine. But lately, she's had some quirks about her.... The radiator fan hardly ever turns on, there's an audible, yet faint clank that is almost perfectly timed with the compression of each piston while driving (I'm treating the engine with high-test so i thought that maybe it was just a big compression for such a small piston causing the noise), and the idle fluctuates a lot. It won't fluctuate itself, It cranks up at around 1200 and will go down only when you mess with the throttle, and after, it usually goes down to a healthy, yet shakey, 600-700.

I want to know what you guys think I should get checked out. What are some things you guys usually go to replace on old, carbureted, cars from like, ~35 years ago? Let me know (':

Her name is Margaret. She chose it, not me.