Belt Drives Vs. Timing Chains By Leonard Emanuelson/autoMedia.com
Are Timing Belts Worth the Added Expense?-
Many performance enthusiasts (especially those on tight budgets), base their selection of engine components simply on cost—do I buy a $75 timing chain or an $800 belt-drive kit? True, both the chain and belt drive rotate the camshaft, but that's really where the similarity ends.
Timing Tuning While a timing chain is nothing more than a traditional internal engine component, a modern belt drive is an invaluable tuning tool that no racer or street horsepower fanatic should be without. Whether you are dyno testing or dialing in your car at the track, you need to be able to quickly adjust the camshaft timing. Camshaft timing is one of the most important tuning aids you can have. By advancing or retarding cam timing, you can compensate for track surface conditions, atmospheric conditions and simply fine-tune every ounce of performance out of your existing combination. The effect of changing cam timing is so significant that many high-end performance cars come from the factory with sophisticated and expensive variable cam-timing devices. For sportsman and bracket racers, it's even more important. If your car isn't hooking up, you can jack it up and make a chassis adjustment that may take 15 minutes or more. Or, with a properly designed belt drive, loosen four bolts and retard the cam timing in the staging lanes in about five minutes—a bracket racer's dream.
Dyno Time Cam timing adjustments can be an important developmental tool on the dyno as well. Not only can you find the "sweet spot" in the power curve, you can move it around to best suit your total engine combination. By experimenting with cam timing and valve lash, a knowledgeable engine builder can determine if he has the best cam for a given application. If not, he may need to run several cams through the engine to find the right one. With a conventional timing-chain setup cam changes are time-consuming, labor-intensive tasks, and with the cost of dyno time these days, you can't afford not to take advantage of all available shortcuts.
Quick-Change Artistry A belt drive can make cam timing changes and camshaft swaps less painful. Cam timing changes can be made without removing the water pump and front timing cover. Camshaft swaps are almost as easy as the camshaft will come out through the front cover without removing the timing cover and oil pan, as is standard procedure with a timing chain. This cuts the time for camshaft changes by at least 60 percent.
There are many more advantages to a belt-drive system than ease of use. A belt drive can increase power over a timing chain through less frictional loss, more precise timing, smoother valvetrain motion and eliminating windage caused by the timing chain and gears running in oil. A belt drive also isolates the crankshaft's torsional vibrations from the camshaft better than a chain (and certainly better than gear drives, which can amplify crank harmonics). Think of it as a second harmonic damper for the rotating assembly. And with all that engine builders are doing to stabilize cylinder-to-cylinder camshaft timing, such as larger-diameter cams, doesn't it make sense to do what you can to precisely phase the camshaft to the crankshaft?