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Timing Issues

Help customers avoid installation problems with advice from suppliers of gear drives, cam drives, pulleys and timing chains.

By Karen Zurvalec


For those selling pulleys, gear drives, cam drives and timing chains, there are a few key factors to keep in mind to help customers get the right product the first time.

“Oftentimes, these components can be very specific to the particular types of racing that they are designed for,” said Cody Mayer of COMP Performance Group, Memphis, Tennessee. “The race environment is very important for the required robustness of the cam drive system. Things to consider are: what kind of forces will be generated by the valvetrain, and is the valvetrain going to be under control during the entire rpm band. Also, are there any sudden changes generated by the application, such as a trophy truck jumping or a prop coming out of the water?

“The most important adjustment when setting up a gear drive system is the backlash,” he continued. “An old trick for this is to run two pieces of newspaper into the gears when setting the backlash. This will give about .010 inches of clearance between the teeth.”

“There are some key factors to consider when deciding to upgrade your timing,” said Jason Thompson of Cloyes Gear and Products, Ft. Smith, Arkansas. “Valvetrain demand is a primary consideration. Camshaft lobe profile, valve spring pressure, rpm range, and horsepower will dictate much of what is necessary for proper timing set selection. Alongside these considerations, the race application is absolutely pivotal to the equation. Circle track racers require a product that will stand up to the demands of the on-and-off throttle abuse, as well as high rpm’s for extended periods of time. Drag racers, in contrast, require a precise rpm, specific launch, and a consistent power curve down the track.

“So many aftermarket high-performance engine blocks are available with improvements over the OE blocks that many builders choose an aftermarket block,” Thompson continued. “This is great, but some of the features on the front of the block may need to be modified to ensure clearance for the timing drive. Prior to ordering a timing set, the engine builder should measure the center distance between the crank and the camshaft. With this measurement, the customer can then call our tech support to select the proper timing set. Accurately matching your timing set to the center distance of your engine will determine the performance and longevity of your timing set.”

“When upgrading a timing set, it is highly recommended to start with a completely matched kit,” advised Ryan Smith of Cloyes.

Thompson added, “Cloyes premium matched race sets are 100 percent verified that the two sprockets and chain as an assembly maintain the correct center distance for the engine application. Random parts just packaged and not verified can result in excessive chain deflection. This results in timing variation, because the cam sprocket is allowed to rotate a certain number of degrees without taking lead from the crank sprocket, which prevents the engine from attaining optimum performance. It also results in chain whip, which will lead to shortened chain fatigue life and can cause ultimate failure. Once the timing set is installed, it should be verified that the chain tightness and alignment are correct. Free slack is too loose. If the chain is so tight that the chain can’t be deflected with pressure, it can cause cam bearing damage. Chain alignment from crank sprocket front face to cam sprocket front face must not exceed .010 of an inch.”

Thompson continued, “Another one of the simplest yet most critical pieces to the assembly puzzle is to torque all the assembly bolts correctly. Racers utilizing the adjustable cam series can also be advised to apply some sort of thread locking compound to ensure that no slippage occurs when you need it most. Many of the high-tech performance products come with installation tips and guidelines in the packaging.”

“There are many things to consider when ordering a belt drive system, and our Tech Department is available to discuss the applications,” said Rob Remesi of Jesel, Lakewood, New Jersey. “Being that a camshaft belt drive uses a mounting cover with the cam, and the crank centers at a fixed location, we often have customers with line bored blocks calling with oil leakage issues at the crankshaft. In this instance, we recommend removing the down pins in the block to allow the cover to re-center itself over the crankshaft before tightening the cover bolts.”

“There really is no such thing as too strong of a timing set, and be cautious of low cost/low end components,” said Marty Staggs of 3pConnect, Rancho Cucamonga, California. 3pConnect handles sales and logistical support in North America for Rollmaster in Windsor Gardens, South Australia, Australia. “A failure in the valvetrain and timing set area can have devastating consequences. This really is not a good area to be conservative.

“Probably the number one problem area when setting up a valvetrain is cam timing,” he continued. “Take your time and degree in your cam. There is a lot of power and reliability to be found if the cam is timed properly.”

“V-belt and serpentine belts are the best choice for power steering or engines with a heavy high pitch fan, as cars without a fan can run HTD without problems,” said Cody Haskins of KRC Steering, Kennesaw, Georgia. “Gilmer and HTD do not work well with a heavy fan because the belts and pulleys work like brake pads, and rotors slow down the fan in deceleration.

“Belt alignment is also very important,” he continued. “Misalignment can rob horsepower and cause premature pulley wear, as well as throw off belts. Make sure aluminum pulleys have a hard anodized coating to extend pulley life.”

“Racers are always looking for tips to help them maintain a fast, reliable race car,” said CJ Jones of Jones Racing Products, Ottsville, Pennsylvania. “One of the biggest areas we are able to help with this goal is to keep the ratios of every driven accessory correct. For example, pumps need certain rpm ranges to move their fluid fast enough to produce the desired pressure and flow characteristics, but too fast can cause cavitation, fluid viscosity breakdown and overheating. Keeping these driven accessory rpm’s correct is key to a fast race car and a reliable race engine,” he concluded.

Additional Content: Visit Performance Racing Industry Magazine online for our comprehensive feature article on Pulleys, Gear Drives, Cam Drives & Timing Chains.




Performance Racing Industry