Uncontrolled torsional vibration can accelerate wear of the main bearings, cause inefficient timing, fracture accessory brackets and worst case, cause the crankshaft to snap – Brian LeBarron
We’ve been testing some of the most common changes you can make in common crate engine racing classes by pitting our own CT-350 through a series of tests on our DynoJet chassis dyno. Now, we’re looking to take the engine to the next level and upgrade the engine to the full advantage of the rules. This means valvetrain upgrades, and some new exhaust, but we’re looking to push the engine beyond even that. Chevy Performance strongly suggests to not race the engine above 5,500 RPM – we’ll be looking to rev to somewhere close to 6,500 RPM.
This will require some key upgrades in the top end of the engine, but we wanted to ensure the force from the hundreds of thousands of explosions exerted on the crankshaft would be controlled properly. After talking with our friends Fluidampr about the project idea, we knew having a damper designed to handle the upgrades would be important as well.
Fluidampr’s CT Gold
At first glance, their CT-Gold series viscous damper (part#62260D) would seem like just another damper on the market, but the CT-Gold damper is specifically designed for race engines to control torsional vibrations above 6,000 RPM. “What we’ve found is that as horsepower rises, the need for a Fluidampr CT Gold is even more important,” explained Brian Lebarron of Fluidampr.
Chevy Performance ships the CT-350 with an elastomer style damper. By design, it is tuned for the stock setup and stock peak torsional vibration frequency range. When you start to modify the engine, two scenarios will typically happen:
1) The torsional vibration frequency range still falls within the limits of the stock damper, but now it is being overworked. With this scenario, early warning elastomer failure signs are cracked, bulging or missing rubber between the hub and the outer inertia ring. As it starts to fail it loses its ability to protect the engine and contributes to inefficient timing.
Does Weight Really Matter?
It’s easy to think, that because the damper is rotating mass on the engine, the you would want to seek out the lightest damper that would fit your engine. This is the correct logic for pulleys, and wheels in most cases, but not dampers. A damper needs a given amount of mass to counter the destructive force of torsional vibration. If the damper is too light it does not adequately protect the engine from torsional vibration. Excessive torsional vibration also means lost horsepower and torque.
Size on the other hand does matter, and having a smaller diameter damper usually does translate to quicker throttle response. The stock damper on the 602 is 8-inches in diameter. The Fluidampr CT-Gold on the 602 offers broader torsional vibration protection at only 6-1/4-inches.