How To Degree A Cam In An LS Engine - Step By Step

This is the most important step in the entire degreeing process. You must accurately determine TDC or all other measurements will be inaccurate. With the piston stop securely in place, carefully turn the engine clockwise until the piston contacts the stop. Record the degree wheel reading-in our case, it was 35 degrees before top dead center (BTDC). Now turn the engine counterclockwise until the piston again hits the stop. The degree wheel will be at true TDC when both piston stop numbers are the same. Let's say the numbers do not agree with 36 on one side and 40 on the other. Halfway would be 38 degrees, so move the wheel to that number and double-check your results.

With TDC now set, we can move on to determining the camshaft's position relative to TDC. This simple illustration reveals the relationship of the intake lobe centerline to TDC. This particular camshaft uses an intake centerline of 109 degrees, which is the number of crankshaft degrees after top dead center (ATDC). This illustration makes it easy to see that if the cam measures 113 degrees ATDC, then the intake lobe is opening and closing later (retarded). Conversely, if the intake centerline is at 104 degrees ATDC, it is opening and closing earlier, which means the cam is advanced relative to TDC.

Armed with this knowledge, we can now measure the actual cam position in the engine. We attached the very cool aluminum dial indicator fixture to the small threaded hole in the block for the plastic lifter holder. Position the dial indicator using the 5-inch extension to align the plunger with the edge of the lifter.

Place the dial indicator plunger extension on the edge of the lifter body as shown. Do not use the pushrod cup because its radius will cause erratic readings. Rotate the engine through several revolutions to ensure that the dial indicator is positioned properly so it reads maximum lift and always returns to zero.

Comp Cams recommends checking cam position using the intake centerline method, which is pretty simple. First rotate the engine until the dial indicator reaches maximum lift and then zero the indicator. Turn the engine counterclockwise until the indicator reads 60 to 70 degrees on the opening side of the lobe. Now rotate the engine clockwise until the indicator reads 0.050 inch before max lift.

With the indicator on 0.050 before max lift, read the degree wheel, which in our case is 65 degrees ATDC. Record this number.

Next, rotate the engine clockwise past max lift until the indicator reads 0.050 inch on the closing side of the lobe and record the number on the degree wheel. In our case, the second reading produced 149 degrees ATDC. Using these two numbers, we can find the true position of the intake centerline.

All we have to do to determine intake centerline is add the two numbers together and divide by 2. So adding 65 + 149 = 214/2 = 107 degrees ATDC for the intake centerline. Looking back at installing the crankshaft sprocket, we advanced the cam 2 degrees, which is what we now have. So by resetting the crank sprocket at 0 (retarding the cam 2 degrees), the intake centerline will be a true 109 degrees ATDC.

This is the digital version of a Comp cam card. The card supplied with the camshaft also includes intake and exhaust opening and closing points at 0.050-inch tappet lift.