Engine Systems
Presumably you know the type of engine you want to use. Odds are you probably made that decision before you decided on the car! You will ordinarily have two options - carburettors or electronic fuel injection. The principles are the same regardless of engine choice - you will either use the factory ignition/EFI system or you will use an aftermarket electronic ignition/computer. I say the same because both need one power feed to the ignition system for the engine to run, another for the starter motor, wires to and from the alternator and the various sensors/senders for the instruments.
All an EFI motor has in addition is a bunch of wires hooked up between some additional sensors or injectors and the computer brain. What these wires do is take the place of the passages in the carburettor and linkages between extra throats etc. This is why an intact EFI loom is such a bonus - plug it on the engine one end, into the computer on the other, and there is only about half a dozen extra wires you need to worry about. Half of these are for the gauges/warning lights while the rest are there to keep the computer's memory alive (a factory computer constantly adjusts the engine’s tune to get absolute peak performance and needs to remember where it is at otherwise it has to start again), tell it when to use the 'choke' to help start the engine and to let it know to keep the engine running. It really isn’t much more complicated than that.
If your loom has been cut or a chunk is missing (ie you have the engine loom to the fire wall and just the wire stubs from the computer) all is not lost - all you have to do is splice in the missing bits. Naturally a diagram helps. Here’s a tip - if you don’t know which plug wire is which, take the top off the computer (and whatever you do, do not touch the circuit inside - static electricity on you that you cannot even feel is enough to fry the electronics) and look at where the plug terminals mate with the circuit board - they should have a little abbreviation for each connection that will correspond with the wiring diagram. This can be made easier by getting a diagram that identifies each wire on every plug, but you can work around it.
Aftermarket systems are simple - just use the wiring loom and diagram supplied. If you use a factory system, especially EFI, then it is absolutely essential that you get your engine supplied with the complete engine loom (or at least both halves if it has been snipped at the fire wall), computer, sensors and wiring diagram otherwise you could be in for a lot of money to get it to go. It is unwise to mix and match any of the EFI system components - some automatic engines run different computers which also control transmissions and things, and an EFI computer programmed to run an airflow meter system will not run a Manifold Absolute Pressure (MAP) sensor system. All these do is tell the computer how much air the engine is sucking in, so it knows how much fuel to give it. Of course there are always ways around this, the easiest being with an aftermarket computer, but these do not come cheap. As always it is a lot easier if you get the right bits to start with.
