some advice from an installer who did competition cars long ago
by
-First, alarm quality is important. Get a good brand.
-However, 90% or more of the quality of an alarm is determined by the install.
-Unless you have a friend or pay bunches of extra for the install, even the best of shops default to a "pretty good" installation. Thus, I recommend installing yourself. It'll take some time to do right, but it makes all the difference.
Basically, a 'standard' install includes the 'brain' being installed under the driver's side dash where most of the necessary wires will be right there. The unit will be well out of sight, and wiring will be neatly arranged into stock harnesses. Wiring should be soldered in, but I know of several shops that still use crimp connectors. Now I admit a good crimp connection CAN be pretty solid, but only if done right, and many aren't - but even if they are, crimp connections stand out like a sore thumb. There will be a single siren in the engine compartment, probably 125dB or so. The alarm will be triggered by impact or door trigger. Might or might not have additional triggering on hood or trunk. The shock sensor will probably be too sensitive.
In comparison, a really well installed alarm will:
-Have the brain located somewhere else. The first place a thief will look is under the dash, driver's side. Try under the carpet underneath the driver's seat. Yes, you have to take out the seat to get to it. That's a GOOD thing!
-All wires will be COMPLETELY integrated into the stock wiring looms. A thief knows to look for the red and yellow non-factory wires and cut. If the wires are actually INSIDE the factory looms, and taped or tied in the same way as factory, they're not nearly so easy to identify. Remember that nearly no factory wires are ever by themselves!
-Tie the alarm in to the horn. Especially if it's a loud horn.
-Use multiple sirens. One in the passenger compartment is a good idea, another in the engine compartment, and another in the rear undercarriage somewhere out of harm's way. Use different brands, that way it sounds like several alarms going off and people will pay more attention.
-SET THE SHOCK SENSOR PROPERLY! it should NOT go off when loud thunder strikes, or when a person leans on the car, or when a semi jake brakes nearby.
-Display the LED prominently. Deterring before they break your window is better than after.
-Protect all entry points. A simple pin switch on the trunk and hood.
-Battery back-up.
Additional security tips:
-Bolt all your amps and other things down with non-standard screws. Thieves generally bring phillips and flat and maybe a socket set. http://www.mcfeelys.com/product/0806-PSL/8-x-34-Zinc-Plated-Steel-Pan-Head-Screws
Nobody totes a square head
-Make sure the stereo itself is bolted internally. If you can bolt into the iso holes in the side of the stereo to something inside the dash, great - if you can't, ensure that you at least have the backstrap bolted to something inside.
-Make sure to keep your 'snatchables' either out of the car or at least out of sight.
I've got more but they're not coming to mind right now and I gotta get back to work. As some people have said here, if a thief really wants your stuff, he'll get it. But thieves aren't out to get anyone, they're out to get stuff they can sell. And like anyone out for money, they're looking for the maximum amount in the minimum time. Make sure your stuff isn't worth their time and they'll move along to an easier target. The above will make sure that only a real hardcore alarm expert will be able to disable it, and honestly, if they're that skilled, they're not going to be messing with an '87 el camino, they'll be looking for bigger $$.
