As you can see, the coathanger makes for a sturdy, easy to read pointer. Here you can easily read the 12 degrees ATDC measurement while zeroing the wheel initially.
“To find top dead center, we’re going to use the .050 [fifty-thousandths of an inch] method, where we measure .050-inch of piston travel before and after top dead center,” Pulido explains. “The .050 method mitigates piston rock, and the crank can dwell for almost five or six degrees at actual top dead center.”
Because this is setting the basis for all of your future measurements, getting this right is critical, and special care should be taken on this step. “If you mess up or overshoot your target, just back up and bring it back in,” comments Pulido. He also notes that you should always arrive at your number by rotating the engine in its natural direction of travel.
Before starting you need to set your dial indicator at a rough zero by passing through TDC several times, and resetting the zero mark of your indicator at the peak lift point.
“For the first reading, we have 12 degrees before top dead center,” Pulido says as he rotates the engine to a .050-inch reading on the dial indicator. Once you record that number, continue to rotate the engine through top dead center until the dial indicator drops back to .050-inch indicated in the bore.
“You’ll notice that as the dial indicator hits zero, it stays there for a few degrees of rotation before coming back down,” says Pulido, pointing out the piston dwell at TDC and why just zeroing on the peak could induce error.
“As the needle returns to .050, our pointer shows 12 degrees after top dead center. That tells us the degree wheel and pointer are properly aligned,” says Pulido.
Once you’ve gotten a solid zero on the degree wheel, you’re ready to start degreeing the cam. Without a solid zero, you’re just guessing at everything else.
Degreeing the Camshaft
With a perfect baseline reference set, now it’s time to actually start measuring camshaft position. “You’ll need your cam card for the next step,” says Pulido. “For this particular camshaft, we have a lobe separation angle of 106 degrees, with one degree of advance in it, so we’re looking for 105 degrees, using the intake centerline method.”
The intake centerline method, as the name suggests, uses the centerline of the number one intake lobe to determine the orientation of the entire camshaft. “What we want to do now, is find the peak lift of the intake lobe of the camshaft so that we can set the dial gauge on the lifter to zero at the peak.”
When degreeing the cam, you need a reliable way of measuring the cam lobe lift, whether its a solid lifter or a checking lifter.
The process for this is very similar to what was done to zero the degree wheel initially, except that lift is being measured at the lifter (to measure the cam lobe directly). “Once I find that intake lobepeak, and set zero on the indicator, I’m going to back up 0.100” on the indicator,” explains Pulido. “Then I’m going to move forward in the natural rotation of the engine back to .050-inch [before peak] on the indicator, and record that number.”
That number is 62.5 degrees in this particular case. Write that down.
“Next, we’ll rotate the crank through the peak of the cam lobe lift and back down to an indicated .050 inch,” says Pulido.
On this cam, that next reading is 147.5 degrees on the degree wheel. Write that down.
“Now, since we’re trying to find the center of those two numbers, you’ll add those two numbers together and divide them by two,” Pulido explains. “In this case, 62.5 + 147.5 = 210. 210 divided by 2 = 105. So we’re right on where the cam card wanted us to be.”