How to use a piston stop?

[R.J.]

It seems that Comp Cams and Crane Cams directions are a little different and I would like to know which one is correct. Both procedures are listed below and the major difference is highlighted. It seems that Comp has you turn the wheel to the average of your two points. Crane wants you to adjust the piston stop until the two stop points are exactly the same and that is your TDC? I can see how they would both work but I think Crane's is more exact. Who has done this before? Thanks


CRANE CAMS
Begin the procedure by first mounting the degree wheel on the end of the crankshaft securely, and rotating the engine to approximately T.D.C. Mount the pointer and line it up at zero on the degree wheel. Now rotate the engine to move the piston down into the cylinder. Install your positive stop device into the spark plug hole and extend the bolt. Now hand turn the engine (do not use the starter motor or you will put a hole through the piston), rotating until the piston comes up and stops against the bolt. Look at the degree wheel and write down the number of degrees shown by the pointer.



Hand turn the engine in the opposite direction until the piston comes up and stops on the bolt again. Go back to the degree wheel and write down the degrees it now reads. Add these two readings together and divide the answer by two. Now either move your pointer by this many degrees, or carefully loosen the degree wheel (without disturbing the position of the crankshaft) and move the wheel this required amount. Re-tighten the bolts, and rotate the engine again making sure that the readings on each side of T.D.C. are equal degrees away from zero. If they are, the zero on the degree wheel will now be the true T.D.C. point. Remove the positive stop device from the spark plug hole, as this procedure is complete.





COMP CAMS

: Position the #1 piston at Top Dead Center (TDC). Attach the degree wheel to the balancer or crank

socket, and install the assembly on the crankshaft. The crank may be rotated from either the front or from the

flywheel end. Obviously, if the engine is in the car, you must rotate from the front. Remember, the greater the

leverage, the smoother the crank rotation, and the more accurately you can rotate the crankshaft. Install degree

wheel and pointer, and set the pointer to zero on the degree wheel. Note: Never use the starter to turn the

engine while degreeing a cam.

Step 3: Rotate the crankshaft opposite the engine rotation direction about 15-20 degrees. This will lower the

piston enough to permit the installation of the piston stop in the #1 spark plug hole. Rotate the crankshaft

clockwise until the piston hits the stop, and record the number indicated on the degree wheel. Next, rotate the

crankshaft counterclockwise until the piston hits the stop from the other direction, and again record the number

on the degree wheel.

Step 4:

Remove the piston stop after marking the two points on the degree wheel. Rotate the crankshaft to the

midpoint of the two marks (this is determined by adding the two points on the degree wheel together, then

dividing by 2). This point is TDC for cylinder #1.Without rotating the crankshaft adjust the degree wheel to read

0 degrees at the pointer. You are now ready to locate the intake lobe center line relative to TDC. If you are not

absolutely sure that your zero degree mark is set at TDC, repeat this procedure. This step is critical to proper

camshaft alignment.

 

[R.J.]

Sorry I did not highlight the differences:

Crane
-Add these two readings together and divide the answer by two. Now either move your pointer by this many degrees, or carefully loosen the degree wheel (without disturbing the position of the crankshaft) and move the wheel this required amount. Re-tighten the bolts, and rotate the engine again making sure that the readings on each side of T.D.C. are equal degrees away from zero. If they are, the zero on the degree wheel will now be the true T.D.C. point.


Comp
-Remove the piston stop after marking the two points on the degree wheel. Rotate the crankshaft to the midpoint of the two marks (this is determined by adding the two points on the degree wheel together, then dividing by 2). This point is TDC for cylinder #1.

So the way that I look at this is if I get 40 and 40 for measurements then with Comp my TDC would be at 40 (40+40 = 80 : 80/2 = 40)
With Crane 40 and 40 would be TDC at zero

 

[final5-0]

Yes you got it

Usually you get a bit higher reading on one side of zero on the first test

Like say 24 and 20 ... so you add em and split the difference

Move the wheel to zero and check again

Most important part is .......
You finish up the procedure with equal values on both sides of zero

Grady

 

[R.J.]

I almost got it. when you add your numbers 24 + 20 you get 44. 44/2 = 22 What do you do with the 22?
This is the way Comp explains it but then they say your done 22 on the wheel is TDC?!?!

I think Crane is trying to say subtract the low form the high (24-20 =4) divide the difference in half (4/2=2) Now 2 deg on the high side is your new starting point. This will lower the 24 to 22 and raise the 20 to 22. Correct?

 

[R.J.]

Here is a right up that i put together, as directions for my self and anybody who needs them once I get it correct. This is a combination of Comp Cams and Crane Cams procedures on their web sites. What would you do differently? Thanks

DEGREEING CAMS

TOOLS NEEDED
-DIAL INDICATOR AND MAGNETIC BASE
-DIAL INDICATOR EXTENSION ROD
-DEGREE WHEEL
-MAGNETIC BASE PLATE
-SOLID LIFTER (OEM WELDED FULLY EXTENDED)
-STEEL PLATE FOR MAGNETIC BASE TO STICK TO
-PISTON STOP (COMP Cams® Part #4795)
-CRANKSHAFT SOCKET (COMP Cams® Part# 4798)

PROCEDURE
1. Remove valve covers.
2. Remove timing chain cover if you plan on making adjustments to the cam sprockets.
3. Wedge a piece of wood behind the moveable timing chain guides to take all of the slack out of the chains.
4. Remove cam followers (rocker arms)
5. Remove the #1 cylinder intake lifter and install the solid lifter in its place.
6. Reinstall the #1 cylinder intake follower.
7. Install the degree wheel on the crankshaft, using the crankshaft socket and set up the pointer.
8. VERY IMPORTANT STEP!! Find Top Dead Center (TDC), on the compression stroke, of the #1 cylinder piston.
-Remove #1 cylinder spark plug
-Rotate crankshaft clockwise until pressure is felt blowing out of the spark plug hole.
-Once pressure is felt, the next time the damper’s “0” mark lines up with the timing pointer, you are at TDC.
9. Adjust the degree wheel pointer to read “zero” (0*) on the wheel.
10. Find TDC on the degree wheel.
-Rotate engine counter clockwise @15-20 deg.
-Install piston stop in #1 cylinder. The piston stop is adjustable, but the only thing that is important about the adjustment is that the piston can make contact with the stop.
-Rotate the engine clockwise until the piston makes contact with the stop. Record the number indicated on the degree wheel.
-Next rotate the engine counter clockwise until the piston makes contact with the stop again. Record the number indicated on the degree wheel.
- If the recorded numbers are different then divide the difference in half (X) and reset the degree wheel to (X) on the high numbers side instead of zero.
-Now starting from (X), repeat the piston stops and record the numbers again. Repeat dividing the difference in half and readjusting the degree wheel until the degree wheel numbers on both the clockwise and counter clockwise stops are the same.
Example: First stop = 35 deg
Second stop = 47 deg
Difference = 12
12/2 = 6
Start the next set of rotations on 6deg from the 47 deg side
-When the numbers are the same then “0” on the degree wheel is you prefect TDC.
11. Remove the piston stop and turn the crank until the “0” (TDC) on the degree wheel lines up with the pointer.
12. Set up the dial indicator magnetic base. (Steel plate is for bolting to the head if current engine configuration allows)
13. Configure dial indicator so that the indicators pointer is resting on the top of the valve spring retainer of the intake valve and is parallel to the valve stem.
14. Set the dial indicator to “zero” (0).
15. Rotate the crank shaft to find MAX LIFT on the #1 cylinder intake valve. (MAX LIFT is the instant that the dial indicator changes directions during its sweep)
16. Once you are at MAX LIFT set the dial indicator to “zero” (0) again.
17. Rotate the crankshaft counter clockwise until the dial indicator reads .100, and then rotate the crankshaft back clockwise, stopping at .050 before max lift.
18. Look at the degree wheel and write down the measurement.
19. Continue rotating the crankshaft clockwise until the dial indicator goes past “zero” to .050 on the closing side of (or after) max lift.
20. Look at the degree wheel and write down the measurement.
21. Take the two numbers that you got form steps 15 and 17. Add them together and divide buy 2. The resulting number will be the location of max lift of the intake lobe in relation to the crank and piston. This is the intake centerline.
-Example: #15’s reading was 100* and #17 reading was 120*. 100*+120*=220*. 220*/2=110* deg this makes your intake centerline, 110 deg
22. Look at your cam card (came with your aftermarket cam) and compare the center line that you figured to where the center line is supposed to be. If your cam card says 112* then your timing is retarded 2* and needs to be advanced 2*. To summarize: Lowering your intake center line will advance your cam and raising your intake center line will retard your cam.
23. Now repeat this process on the #6 cylinder for the other cam. With one exception, you do NOT have to get TDC for the #6 piston.
24. The first step (after installing the solid lifter and follower on the intake valve) will be to get max lift.
25. At this point start at #11 of this process and repeat back to #22