The simplest method to check if the cam is installed according to the cam card is to compare the opening and closing points at 0.050-inch intake valve opening and closing points. Unfortunately, Comp only lists its opening and closing points at a 0.015-inch checking height. We tried checking the cam at 0.015 inch to see how close we could get to the specs. With the lifter on the base circle, turn the crank clockwise until the dial indicator reads 0.015 inch and then record the number on the degree wheel. Continue to turn the crank clockwise until you read 0.015 inch on the closing side and record that number. Comp lists the intake opening spec at 40 degrees before top dead center (BTDC), while we measured 39 degrees. Comp's intake-closing spec is 72 after bottom dead center (ABDC), while we measured 74 degrees. There's a quick equation for determining lobe duration: Intake opening (I.O.) + intake closing (I.C.) + 180 degrees = duration. Comp's published spec for this cam is 40 I.O. + 72 I.C. + 180 = 292 degrees at 0.015-inch checking height. But when we added our numbers: 39 + 74 + 180 = 293 degrees, something wasn't right. We double-checked our TDC and all the previous measurements, but the numbers came out the same. Assuming the cam is correct for a moment, measuring the cam at the 0.015-inch checking height isn't accurate because this checking height is too close to the base circle where the cam is rotating more degrees for each 0.001-inch lift. Checking the opening and closing points at 0.050-inch tappet lift would be more accurate, where the lobe is moving a fewer number of degrees per 0.001-inch tappet lift. Comp doesn't list its numbers at 0.050, so we had to find another way. Next, we performed the intake-centerline method of checking the cam's position and found it to be within 11/42 degree of right where it should be. Comp's spec is 106 degrees intake centerline, and we measured 106.5 degrees. This appears to be much more accurate, so we chose to believe that number instead of the opening and closing numbers at the 0.015-inch checking height. It's also important to note that not all degree wheels are labeled the same way. Most are numbered like the Comp Cams wheel as 0-90-180-90-0. But we've seen some wheels marked at 0 to 360 degrees. Sometimes you have to count backward from 180 to get the numbers to come out correctly. This was true with our cam for the intake-closing numbers. Intake-Centerline MethodThe intake-centerline method does not require any special setup, but it does require some simple math, so go find your calculator. Begin by rotating the engine clockwise until the dial indicator reads max lift. Zero the dial indicator and rotate the engine counterclockwise until the dial indicator reads roughly 0.100 inch down from max lift. Slowly rotate the engine clockwise until the dial indicator reads 0.050 inch from max lift and record the number on the degree wheel. Next, continue to rotate the crankshaft clockwise until the dial indicator reads 0.050 inch on the closing side of the intake lobe from max lift and record that data. Once you have TDC accurately located, merely rotate the crank clockwise and record the intake opening and closing numbers at the lobe checking height. Comp's specs were listed at a lash of 0.015 inch. Here, intake opening occurs at 39 degrees BTDC. Once you have TDC accurately located, merely rotate the crank clockwise and record the int We continued to rotate the cam through to 0.015 inch on the closing side and recorded a figure of 74 degrees ABDC. This wheel indicates degrees 0 to 180 from TDC to bottom dead center (BDC). But to read the numbers as "after bottom dead center" we must count counterclockwise from the 180-degree mark to the pointer. This indicates 74 degrees ABDC, not 106 BTDC. Most cam cards specify the before and after numbers to make this easier to understand. This little idiosyncrasy trips up a lot of people, so watch out for it. We continued to rotate the cam through to 0.015 inch on the closing side and recorded a fi The cam-checker tool comes with both a roller cam and a flat-tappet cam follower for both types of camshafts. The cam-checker tool comes with both a roller cam and a flat-tappet cam follower for both We also used this Powerhouse cam-checker tool that mounts the dial indicator directly to a housing that fits in the lifter bore. This is much quicker and easier than setting up a magnetic base and dial indicator. We also used this Powerhouse cam-checker tool that mounts the dial indicator directly to a « | 1 | 2 | 3 | 4 | » | View Full Article Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!