I would never suggest taking out a loan to hook up your car.

What you have to do is:
1) Figure out how how long you are going to take to complete your car (i.e - timeframe)
2) Figure out how much cash you can spend on the car during that amount of time (allow for problems in life also)
3) Prioritize the work (i.e, engine, body, audio, etc - order of work0
4) keep working ideas and numbers until they lineup
5) follow through with your plans (very important)

Remember: Don't try to do more than you can afford. In other words, do plan to build a 8 sec drag car, if you only have $2K total available over 2 years.

I have 4 toys right now, and even with what I make, I have a budget for each of them - and a time frame to complete it in.