In the high-stakes world of racing, particularly drag racing, the meticulous attention to engine detail is paramount. A common sight in the pits is racers meticulously inspecting their engine's valvetrain, checking valve spring pressure and setting valve lash. This dedication underscores the importance of maintaining a healthy valvetrain, especially considering the increasing sophistication and cost of modern valvetrain components. This article explores the tools and techniques essential for precise valve lash adjustment and valvetrain maintenance, focusing on tools like the LSM Valve Lash Adjusting Torque Wrench and Valve Spring Seat Pressure Tester.
Valve spring pressure is a critical factor in valvetrain performance. When examining a valve spring spec sheet, two types of pressure are typically listed: open pressure and seat pressure. Open pressure refers to the force exerted by the valve spring when the rocker arm is at maximum cam lift. However, checking open pressure with the valvetrain installed is often impractical. Therefore, seat pressure, the pressure exerted when the valve is closed, is the more commonly measured value. Valve spring manufacturers usually provide the recommended seat pressure for a specific setup at a specific installed height.
Deviations from the recommended seat pressure can lead to significant problems. Excessive seat pressure can cause catastrophic engine failure. One example is a customer who installed overly stiff roller cam springs on a big block Chevy crate engine without following recommendations. The result was a broken camshaft and extensive damage to the engine.
A valuable tool for measuring seat pressure is the LSM Valve Spring Seat Pressure Tester. This tool is compatible with both shaft mount and stud-mount rocker systems installed on the engine. It features a liquid-filled gauge for accurate readings and an adjustable shim pack for precise setup. The LSM seat pressure tester also includes a multiple handle option. The short handle is useful when working around obstructions like brake boosters or master cylinders. The handle extension is then used to complete the remaining springs. The gauge can also be swiveled for better clearance. By adjusting the position of the tool load rollers in the frame and using the shim pack, you can adjust the tool centerline-to-rocker roller tip centerline distance.
To use the LSM tester, install it on a rocker arm and gently rock it side to side to square the roller on the rocker body. Then, pull the tester toward you and slide its hook onto the pushrod. This centers the load roller and applies pressure to the gauge. Pull the tool’s handle until you feel the valve come off the seat. Again, gently rock the pressure tester side to side a few degrees to double-check that the tool is square against the rocker body. Finally, take the pressure reading on the gauge.
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Another critical aspect of modern valvetrain maintenance is ensuring proper torque on the rocker arm jam nuts. Over-tightening can crack a jam nut or cause it to seize in the rocker, especially in shaft-mounted aluminum rocker arms. Conversely, under-tightening can lead to the adjuster nut coming loose.
The LSM Valve Lash Adjusting Torque Wrench is designed to address this issue. This tool has a hollow 3/8-inch drive that accommodates a socket of the appropriate size for the adjuster nut. The included T-handle fits through the socket, with a bushing to keep it square.
To use the tool, loosen the adjusting nut and adjust the adjusting screw to achieve the desired valve lash specification. Double-check the lash using a regular feeler gauge. While the LSM wrench was initially designed for shaft-mount aluminum rockers, it can also be used on stud-mount roller rockers. For stud-mount rockers, the set screw in the poly lock is torqued, not the adjuster. To use the TQ-100 on stud-mount rockers, attach a 3/8-inch drive, 7/32-inch hex/Allen bit socket and use a box wrench. Loosen the set screw in the poly lock with the TQ-100 and the hex/Allen bit socket.
Besides the LSM tools, various other valve lash adjusting wrenches are available. These include wrenches with different sizes and combinations, such as:
The LSM Universal Valve Lash Adjusting Tool is designed for adjusting valve lash on 602's, 603's and 604's. It requires a standard 1/2" drive socket and the correct hex key. The LSM "One-Tool" features a knurled anti-slip handle and is designed with the correct length for tightening adjuster nuts. It includes four bushings to accept additional sizes of T-Handles and comes with a 3/16" T-handle.
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tags: #valve #lash #adjusting #tool #types
