You've already chosen the chassis. Now it's time to add the horsepower. But, so many choices of engines are available that it's easy to get lost in the sea of specs, horsepower ratings and the advice of fellow drivers. Let Horizon Hobby Surface Product Manager Bill Jeric cut through some of the misinformation and provide some easy-to-follow guidelines that will help you make an informed decision.

4-wheel-drive nitro touring cars have the ability to hook up lots of power and prodigious amounts of bottom-end torque. For absolute top performance in touring cars, I recommend either a side exhaust or rear exhaust engine with a slide valve carb. Slide carbs provide the instantaneous throttle response necessary for top-level competition on prepared racing surfaces. However, novice drivers and "street racers" will find the "on/off switch" response difficult to control (particularly on slippery surfaces) and may wish to consider a rotary carburetor. The choice of side or rear exhaust is largely up to you-just determine which configuration works best for your chassis. Some chassis, for example, will only accept rear exhaust engines, while others are designed exclusively for side exhaust installations.

The biggest challenge facing nitro truck racers is one of "driveability". Today's .12 engines produce so much power that it's becoming increasingly difficult to put that power to the ground without constantly breaking the tires loose.

Because of this, more than half of all professional drivers choose engines with rotary carburetors, due to their smooth throttle response. However, if you tend to run on tracks that have a lot of grip and forward traction is never an issue, you may want to consider a slide valve carb. The Losi XXX-NT and Associated RC10GT both accept either side or rear exhaust engines, so exhaust configuration becomes a matter of personal preference.

For many off-road enthusiasts, driving 1/8-scale buggies is the ultimate thrill. The combination of a stable platform, four-wheel drive and outrageous braking power makes these cars the king of the nitro off-road hill. It takes some serious ponies, however, to move these 7 1/2 pound beasts to speeds approaching 50MPH. Keep in mind, though, that if you're into enjoying 1/8 buggies by driving around the local park or ball field, the latest 8-port turbo hand-polished Whizbang .21 will most likely be a waste of your funds. Who among us can tell the difference between 40 and 50MPH when driving an off-road buggy? At those speeds, both vehicles are at the ragged edge of control anyway! Key issues to keep in mind when making your choice are the quality and general reputation of the manufacturer, the suitability of the engine to your buggy (do not put on-road "turbo" engines in off-road buggies!), and the need (if applicable) for a recoil starter. All engines in this class use a slide valve carburetor, and the linkage system in your buggy is designed for this.