Tech Article: How to Degree Aftermarket Cams

[Moai]

[Originally written by ChrisK on mr2oc.com]


The cam gear helps you to adjust your cams to the correct lobe center.
Setting the cams to zero on the cam gear means absolutely nothing and might even in some cases be harmful. Cams should be adjusted in correlation to the position of the crankshaft.

For example:
Lobe centers on the 3SGTE HKS 264’s are 110º for the inlet cam and 103º for the exhaust cam. Adjusting your cams to these specs will most probably bring them very close to their maximum designed performance. After all, why purchase a part that can add power and then install it in a way that it doesn't work as designed?

Ok, a lobe center of 110º on the inlet cam means that maximum valve opening will be at 110º ATDC and 103º on the exhaust will mean that maximum valve lift will be at 103º BTDC

This is how I [Chrisk] degree my cams:

1. Use a pencil, paper and arithmetic for this procedure, to keep track of the results.

2. Fashion a rigid pointer from stiff wire or an old coat hanger and attach it to the engine block. This pointer locates the degrees on the degree wheel.

3. With a degree wheel installed on the crankshaft, rotate the crank to get the #1 piston at TDC and check to ensure that the valves are fully closed then adjust the pointer to zero (0º TDC) on the degree wheel.

4. Turn the crankshaft opposite the running rotation approximately 15-20 degrees. Install a piston stop on the top of the engine block fastened in place by two head bolts.

5. Continue to turn the engine in the same direction until the piston comes back up and just touches the piston stop. Make a note of the exact number on the degree wheel that the pointer is on.

6. Rotate the engine in the other direction (running rotation) until the piston comes back up and touches the piston stop. Again note the number where the pointer is.

7. Remove the piston stop and rotate the crankshaft to the midpoint of the two marks. At this point the piston is at the true top dead center. Loosen the degree wheel and adjust it so it will read 0º TDC at the pointer. Don't rotate the crankshaft to do this!

8. Now, it's time to locate the lobe centerline relative to TDC. Attach a dial indicator on the top of the engine block. Set the tip to contact the top of the #1 cylinder inlet valve shim/bucket. Check to make sure that the indicator plunger is parallel to the valve stem. NOTE - any variance in an angle will produce geometric errors in the lift readings.

9. Rotate the engine in the normal direction of rotation until a reading on the dial gauge of 0.040” lift is reached. (Valve will start to open) Mark the dial gauge and make a note of the reading on the degree wheel.

10. Continue to turn the engine in the normal direction past maximum lift. The valve will now return to its close position. Make a note of the degree wheel reading when the indicator reads 0.040" on the return side

11. Now add the larger of the two readings that you noted on the degree wheel to 180 subtract the smaller number and then divide the answer by two. Your answer will indicate the lobe center of the cam. Example: open reading was 4 and close reading was 43. Now add 43 to 180 = 223, subtract 4 =219 divide by 2 = 109.5. Lobe center is 109.5 degrees.

12. Continue to move the cam on the adjustable cam gear and redo steps 10 to 12 until the required lobe center is achieved.

13. Now do the same for the exhaust cam.

For those of you too lazy to make your own, you can download one and print it out from here:
http://www.tavia.com/free_degree_wheel.html

[AussieDan]

Nice work (even if you stole it from ChrisK )

[Moai]

hey, why mess with success?

[Timdog1650]

are you sure 4 hundreths of an inch is the amount of valve lift you want to be measuring by? I've heard 5 THOUSANDTHS of an inch is the standard on US cars for measuring valve lift when degreeing an engine.

[Slow02GT]

Here's athread regarding degreeing aftermarket cams specifically for a mustang, if anyone ever needs it!

http://forums.modulardepot.com/showt...threadid=55904

[mikecentola]

wow this is old lol, but good information!!!

[mikecentola]

stuck too!