Performance & Hotrod Business - July '15

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10 n PRECISION ENGINE n July 2015 PRECISION ENGINE L ate-model production engines feature both camshaft and crankshaft position sensor circuits in order to inform the ECM about crankshaft and camshaft positions, which allows the computer to determine ignition timing. Many crankshafts feature a press-fit toothed timing wheel, referred to as a reluctor wheel. A magnet sen- sor mounted stationary in the block is aligned to the wheel and picks up crankshaft position. Since the GM LS engine plat- form is an extremely popular choice for many performance vehicle builds today, we'll use the LS engine as our example. Tooth Talk LS engines feature a toothed reluctor wheel (also called a tone wheel or tone ring), which is press-fit onto the rear of the crankshaft. This toothed wheel is used by the crankshaft position sensor for ignition timing. There are two styles of wheels. The Gen III LS1/LS6/LQ4 engines originally used the 24-tooth reluctor wheel, while the Gen IV LS2/LS7LS3/LS9 engines fea- tured a 58-tooth wheel. In most cases, you can identify a Gen III or Gen IV by the location of the camshaft sensor. Gen III engines featured the cam sensor mounted at the top rear of the block, while Gen IV engines feature the cam sensor mounted onto the timing cover. This is important to note for those who plan to use an aftermarket timing control unit, such as MSD's 6LS timing control module. MSD's 6LS module part number 6010 is designed for use with the 24-tooth wheel, while its 6LS-2 part number 6012 is designed for the 58-tooth wheel. Either tooth-count wheel can be installed on any LS crank, as long as you have a controller designed for the specific tooth-count. If you're starting from scratch and have a choice, it's best to go with a 58-tooth wheel and matching controller for more accurate timing control. If you opt to buy an aftermarket perfor- mance crankshaft (let's say you're building a stroker engine, for example), the crankshaft may or may not include a reluctor wheel. In either case, pay attention to the number of teeth on the wheel. If you plan to use the factory engine management computer, you'll need to stick with the same version (24- or 58-tooth) of the wheel that the engine's controller originally used. If you plan to use an after- market controller, it really doesn't matter, as long as you buy the correct timing control- ler that matches your wheel's number of teeth. While aftermarket ignition controllers may be applicable to both fuel-injected and carbureted engine applications, if you're prepping an LS engine and plan to go carbureted, you must have an ignition controller, and that controller must be If you purchase a new crankshaft and the reluc- tor wheel is not already installed, you'll need to install the wheel, but placement and method of instal- lation is critical. Don't attempt it if you don't know what you're doing, as you can easily ruin the wheel. Crankshaft Reluctor Installation does not involve the use of a hammer! By Mike Mavrigian Wheels LS Here's a Lunati 4.000-inch-stroke forged crank that I bought, with the tone wheel separated. Lunati will gladly install the wheel, but you can buy the crank without it as well.

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