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Video: Comp Shows How To Degree A Camshaft

Installing a performance cam in your street, strip or off road motor is mostly about timing. It’s also about knowing which numbers to average in order to come out with the correct figures. No one knows how complex yet rewarding the performance cam install process is like Comp Cams. In this detailed “how to” video on cam degreeing from Comp, several steps are recommended by the manufacturer to ensure that your performance cam has the most accurate lift and duration:

The Timing Set:

Upon initial install, Comp recommends bolting on your motor’s timing set without the lock plate in case later adjustments need to be made. Of paramount importance in installing the timing set is to make sure that the set is installed with both timing marks facing each other. The timing set on the small-block from Powerhouse Products featured in this video allows for various adjustment settings while making the 0-degree mark visibly clear to the engine builder.

Using Test Springs During Assembly:

As far as as a motor’s valve springs are concerned, the true springs can be used while degreeing a cam. Using the lightweight test springs featured in Powerhouse Products‘ cam degreeing kit is recommended, however.

The reason is because the test springs make it easier to turn the motor during assembly, while allowing the builder to install the valvetrain more accurately. In the case of motors with hydraulic lifters, the excessive force of the motor’s true valve springs can cause the lifters to collapse. For this reason also, use of the test springs is recommended.

Using Adjustable Pushrods Assembly:

Unless you have true pushrods of the correct length, Powerhouse’s adjustable test rods are recommended during pushrod assembly. In this instance, Powerhouse’s lightweight test springs must also be used as the test rods are unable to withstand the force of the motor’s springs, and the test rods will bend.

Lifters:

Applying a lightweight coat of engine assembly lube to the engines lifters upon initial install is crucial. Lubricating the lifters excessively can alter their radii.

For good measure, standard 30W motor oil (not synthetic) can be used if assembly lube is not available. Once they have been lubed, the lifters can be pulled later to be greased over more thoroughly.

Rocker Ratios and Valve Lash:

After installing your pushrods and rocker arms, it’s vital to make sure that all of your rockers are timed and adjusted to where the amount of valve lash is minimal. Excessive lash robs a motor of its performance by restricting valves from reaching their max amount of lift.

Degree Wheel Crank Socket:

There are different ways to attach the cam degree wheel to the motor, but using the recommended crank sprocket from Powerhouse Products promises to streamline the process. This is because Powerhouse’s crank sprocket features a slot that fits over the motor’s crank, with an adjustable screw that allows for minimum wobble during assembly. This allows for more accurate cam degree measurements.

Using The Wire Pointer:

The cam timing kit from Powerhouse Products features a simple wire pointer that easily bolts on to one of the motor’s water pump mounting holes. With the degree wheel installed and held securely in place by a locking collar, the wire pointer is installed as close to the front of the degree wheel as possible without actually touching it. This helps the builder to read the cam degree measurements with accuracy.

Establishing Top Dead Center:

The timing kit also features a piston stop that helps engine builders in establishing Top Dead Center (TDC). The stop threads into the motor’s combustion chambers deep enough to prevent the piston’s full sweep.

Before installing this stop, however, it’s important to use a flashlight to make sure that the piston is down inside the cylinder bore. With the piston stop inserted into the combustion chamber, the motor must be turned slowly in a clockwise direction until the piston stops.

Likewise, the motor must be turned slowly in a counter clockwise direction until the piston stops; the average between these two numbers is the motor’s TDC.

Once the TDC is established, return the degree wheel back to its 0 degree mark and tighten the lock collar firmly into place.

Using The Dial Indicator:

The final step before degreeing-in the cam is to install a dial indicator on the valve’s retainer. The indicator must be set to read off of the top of the retainers, and must be in line with the valve’s stem. The indicator features a user friendly stand that threads into the motor’s valve cover bolt holes, allowing for easy and precise calibration of the indicator.

Since the indicator reads off of the valve retainers and not the cam lobes, it’s crucial to make note of our rocker arm ratios in order to determine how much leverage is actually being produced at the valves. In the case of our featured small-block, the rocker ratio is 1.52:1. This number is multiplied by the lobe lift to figure out how much actual lift is at the valve, in this case 0.076-inch”

Turn the motor slowly clockwise until the dial indicator reads the amount of actual, calculated valve lift. Looking at the degree wheel, count the number of degrees from either TDC or BDC, whichever is closest. If the max lift is 0.076-inch, then you must continue to turn the motor in a clockwise direction until the valves are 0.076-inch away from closing. All measurements must be taken with the motor turning in a clockwise direction, since any slack on the timing chain can throw measurements off if the motor spins backwards.

To find duration, add the sum of your opening and closing numbers to 180 degrees. Assuming that we’ve calculated our duration, we must figure out the intake lobe centerline by rotating the motor clockwise until it’s reached max valve lift, zeroing out the dial indicator from that point. Then, turn the motor back and clockwise until it’s 0.050-inch below max lift, then 0.050-inch over. The intake centerline is the difference between the two numbers given on the degree wheel at these positions.

At this point in the cam install and timing process, most engine builders are satisfied. If not, then the process that has just been described above can be repeated verbatim on the exhaust lobe.

Sources

COMP Cams
Phone: (901) 795-2400


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