What makes the difference in engines?

I'd like to know how companies (ford, Chevy, dodge. Ect) change the engine to make them better besides how many cylinders they have. How do they make different sounds, more or less power? Sense they all have the perfect air to fuel ratio from the factory that would make a difference right?

Ticking noise coming from engine?

Ever since I replaced the spark plugs in my 01 Ford Sport Trac, I've been hearing a clicking noise coming from the engine on the driver's side. One plug I replaced had been cross threaded, so I had to buy a tap to repair the threads in the block in order to get the new plug in. They were Bosch plugs. I read later that Bosch typically doesn't work too well in Ford engines, so I switched 3 of them out with Motorcraft. Still, the noise persists. It starts in idle, but gets louder and more frequent with increase in RPM's, and quiets down when set at a steady speed and decelerating. I have pulled each plug wire off one by one to see if they are the cause, and I still hear it. I feel like it has something to do with the plugs because it started after the initial replacement. Any suggestions on what this could be, or how serious it is? It's very annoying. The vehicle has 203k miles for additional information.

Should I buy a fixer upper?

I'm 14 and I'm starting to worry about driving and getting a truck and so I was on kijiji and found a ford f-100 that comes with 2 extra "parts trucks" and started thinking of the classic storys of guy finds car in the woods and builds it from the ground up so I think that I would be up for the challenge with of course a little help from my dad and uncle and grand father but i don't know if it's a good investment for 2500$ an if so do you think that I will be able to get the money in about one year of work
Also I would like to know if you fixed up a car or truck for your first car

Why is my car shaking still?

I have a 99 ford contour, 4 cyl 2.0 liter engine. In the last few months I have replaced both lower control arms in the front, the ball joint bearing, tie rod end and cv axle on driver side. I replaced my brakes, bought new (used) tires and got my alignment done twice. My car still shakes on the freeway. It has been very hard to get around because I'm too nervous to drive my car like that. I have spent over a grand trying to fix this car. I'm taking it as a loss, but I'm still curious to find out why it would still shake.

Bored of my car, should I sell my Ford Figo?

For a while now I've been considering selling my car. There's nothing wrong with it, that's why I'm asking you all.

Currently, I'm driving a 2012 Ford Figo 1.4 Ambiente which is standing at about 49000km. Besides a couple of tiny scratches from stones from the road or trucks in front of me, it's in pristine condition. Currently, my car can sell for about ZAR95,000. I can buy plenty decent used cars with that money.

I'm looking at cars like a Golf (MK4 or MK5) or something similar - something that is "bang-for'buck" and reliable.

Or, should I just ignore the temptation and stick with my Figo?

In 6 or so years, what will sell earier? A Golf MK4/5 or a Figo?