How to Guide: Degreeing Cams on 6G72 w/ Pictures

[Fakepower]

This is How I degreed my cams, there may be a better way, but it's how i did it. I'd love some feedback

Step 1: Find Top Dead Center (TDC) of Number One Cylinder, The Ignition System Stealth316 gives a good layout and explanation of the cylinder layout. This also becomes critical when degreeing the rear cylinder bank.
- There are various way to do this. I used a dial indicator and rotated the
motor until TDC was found. Notice we used some flat iron secured to the
head via middle valve cover holes to secure the iron and thus the dial
indicator base.



Step 2: Setting the Degree Wheel to 0 degrees at TDC. This is a Comp Cam Degree wheel available on summit, you can see the black insert in the middle, it perfectly fits the stock crank pulley bolt. I used an axle nut on the back to space out the degree wheel from the crankshaft for proper clearance (no picture sorry). I used a pointer also available on summit, and you can see I mounted it to the water pump upper bracket.

ONCE YOU SET THE POINTER AND DEGREE WHEEL YOU CANNOT DO TWO THINGS:
1.Touch the pointer.
2.Rotate the engine counter clockwise as this could loosen the crank bolt and throw off your degree wheel.




Step 3: Insert a Solid Lifter and Setup Dial Indicator on Valve Retainer. You must have a solid lifter. Period. I’ll go into more detail later but you want to keep the solid lifter in a loosen position so you can adjust it in car. Also lower the solid lifter all the way down or down far enough that you are confident that it is not preloading the valve. PRELOADING CANNOT EXIST AT THIS STEP.


When arranging the dial indicator on the valve retainer there are several factors to consider:
1.The dial indicator needs to be on a “flat” portion of the retainer with as little curvature as possible.

2.The dial indicator needs to clear the cam shaft with ZERO touching, bumping, rubbing, etc.

3.The angle of the dial indicator needs to be approximately parallel to the angle of the valve stem in 3 planes. Ie if you could extend the valve stem (red line) into space, that line and the dial indicator (yellow line) need to be as parallel as possible (blue lines showing the space between the lines is approximately equal and hence parallel).



Step 4: Setting 0.005” preload by using solid lifter. You’ve probably done this by now, but the cam lobe must be entirely off the valve, ie not depressing the valve (or more accurately in our case, completely off the rocker arm). If Not Rotate the engine until the cam lobe is pointing straight up from the valve (note: this is not straight up to the sky but straight up from the valve stem, ie use the red line from the last picture).

Zero the dial indicator, rotate the motor a few times to ensure that when you return to the completely off lobe position the dial indicator should return to zero. THIS MUST HAPPEN, if it doesn’t return to zero you have a problem and repeat step 3.

Now lengthen the solid lifter until you’ve added 0.005” preload on the dial indicator and lock the solid lifter.

[Fakepower]

Step 5: Degreeing the Cams. You must have a cam card or detailed cam specifications, in my case I was installing the Brian Crower 272 street cams. NOTE: this cam card won’t work for factory cams or any other cams for that matter. I’ve provided the cam card as an example only. NOTE AGAIN: NEVER ROTATE THE ENGINE COUNTERCLOCKWISE.

Here’s the guide to understanding the abbreviations on the cam card
INT : Intake Valve
EXH: Exhaust Valve
TDC: Top Dead Center
BDC: Bottom Dead Center
ATDC : After Top Dead Center
BTDC: Before Top Dead Center
BBDC: Before Bottom Dead Center
ABDC: After Bottom Dead Center
I.O. : Intake Valve Open
I.C. : Intake Valve Close
E.O. : Exhaust Valve Open
E.C. : Exhaust Valve Close

In the diagram in the bottom half of the cam card, it can be seen: Timing Events Correct at 0.050” Lift , These are the values we will be using.


1.So in the general case, rotate the engine (in the correct direction) until 0.050” lift is achieved on the dial indicator. You need to note the position of the small dial (Red arrow) because this is also the point at which you will be 0.050” from closing. (this picture is just an example, obviously I'm not at 0.050" lift, I just took this picture to show what I was talking about)

2.Note the degree on the degree wheel. (as an example: at 0.050” lift on the intake cam, the degree wheel should be -7 degrees ATDC, this is the same thing as 7 degrees BTDC, I have no idea why brian crower uses the negative system)

3.Continue rotating the engine until you are 0.050” lift from closing (ie the little arrow on the dial indicator will be the same as it was for 0.050” lift after opening in step 1). DONT ROTATE COUNTER CLOCKWISE, Rotate the engine through the full strokes until valve closure occurs.

4.Note the degree on the degree wheel. (example: at 0.050” lift from closing on the intake cam, the degree wheel should be 31 degrees ABDC.

5.Repeat a few times to check your numbers are CONSISTENT (Not necessarily perfectly accurate to the cam card). If not, you have something wrong and the numbers will not be consistent, and go back to step 3 and continue forward again.

6.Now that you have your numbers, using adjustable cam gears adjust the cam timing to the correct for differences.
a.I talked to a couple of people about the best way to do this and in general the consensus is to average the differences. As an example: If you measure the intake opens 4 degrees early and the exhaust closes 2 degrees late, retard
the timing a degree such that the intake opens 3 degrees early and the exhaust closes 3 degrees late. It is believed that the inability to measure directly at the valve stem, and the requirement of the rocker arm for valve depression introduce some 'error' of measurement into the degreeing. Thus the best way is to average the error on both sides of opening and closing and this gives the best timing possible.

7. After adjustment, CHECK to make sure what you just did made the changes you expected. CHECK CHECK AND RECHECK to make sure what you did makes sense.

8.Complete on other cams. Note on the Rear cylinder bank you need to use cylinder number 4 because it is the paired sister cylinder of cylinder 1, and you will not need to reset the degree wheel. SEE Stealth 316 link in step 1.

[Fakepower]

reserved

[Italo Grasso]

Step 5: Degreeing the Cams. You must have a cam card or detailed cam specifications, in my case I was installing the Brian Crower 272 street cams. NOTE: this cam card won’t work for factory cams or any other cams for that matter. I’ve provided the cam card as an example only. NOTE AGAIN: NEVER ROTATE THE ENGINE COUNTERCLOCKWISE.

Here’s the guide to understanding the abbreviations on the cam card
INT : Intake Valve
EXH: Exhaust Valve
TDC: Top Dead Center
BDC: Bottom Dead Center
ATDC : After Top Dead Center
BTDC: Before Top Dead Center
BBDC: Before Bottom Dead Center
ABDC: After Bottom Dead Center
I.O. : Intake Valve Open
I.C. : Intake Valve Close
E.O. : Exhaust Valve Open
E.C. : Exhaust Valve Close

In the diagram in the bottom half of the cam card, it can be seen: Timing Events Correct at 0.050” Lift , These are the values we will be using.


1.So in the general case, rotate the engine (in the correct direction) until 0.050” lift is achieved on the dial indicator. You need to note the position of the small dial (Red arrow) because this is also the point at which you will be 0.050” from closing. (this picture is just an example, obviously I'm not at 0.050" lift, I just took this picture to show what I was talking about)

2.Note the degree on the degree wheel. (as an example: at 0.050” lift on the intake cam, the degree wheel should be -7 degrees ATDC, this is the same thing as 7 degrees BTDC, I have no idea why brian crower uses the negative system)

3.Continue rotating the engine until you are 0.050” lift from closing (ie the little arrow on the dial indicator will be the same as it was for 0.050” lift after opening in step 1). DONT ROTATE COUNTER CLOCKWISE, Rotate the engine through the full strokes until valve closure occurs.

4.Note the degree on the degree wheel. (example: at 0.050” lift from closing on the intake cam, the degree wheel should be 31 degrees ABDC.

5.Repeat a few times to check your numbers are CONSISTENT (Not necessarily perfectly accurate to the cam card). If not, you have something wrong and the numbers will not be consistent, and go back to step 3 and continue forward again.

6.Now that you have your numbers, using adjustable cam gears adjust the cam timing to the correct for differences.
a.I talked to a couple of people about the best way to do this and in general the consensus is to average the differences. As an example: If you measure the intake opens 4 degrees early and the exhaust closes 2 degrees late, retard
the timing a degree such that the intake opens 3 degrees early and the exhaust closes 3 degrees late. It is believed that the inability to measure directly at the valve stem, and the requirement of the rocker arm for valve depression introduce some 'error' of measurement into the degreeing. Thus the best way is to average the error on both sides of opening and closing and this gives the best timing possible.

7. After adjustment, CHECK to make sure what you just did made the changes you expected. CHECK CHECK AND RECHECK to make sure what you did makes sense.

8.Complete on other cams. Note on the Rear cylinder bank you need to use cylinder number 4 because it is the paired sister cylinder of cylinder 1, and you will not need to reset the degree wheel. SEE Stealth 316 link in step 1.

Take a look at the BC Cam Card, the note states set to "0" and then tune from there for best result, well 0 is 109.5 in/106.5 ex for us....BC could have reccomended 1XX in/ex but that wouldn't be zero (0) on our cars...Just to clear up any confusion here is the math from the BC Cam card to show the BC cam "0" is the same as our cars ((180+7+31)/2)=109 CL intake ; ((180+1+33)/2)=107 CL ex...

[RealMcCoy]

Take a look at the BC Cam Card, the note states set to "0" and then tune from there for best result, well 0 is 109.5 in/106.5 ex for us....BC could have reccomended 1XX in/ex but that wouldn't be zero (0) on our cars...Just to clear up any confusion here is the math from the BC Cam card to show the BC cam "0" is the same as our cars ((180+7+31)/2)=109 CL intake ; ((180+1+33)/2)=107 CL ex...

Agreed, but other cam grinders may not be on the same center... If they're using new blanks, they could put the centerline wherever they wanted.

If they wanted 110 centers. They could just use N/A blanks and grind them 1/2 degree off... I wouldn't assume ALL cams are on stock centers.

[Italo Grasso]

Agreed, but other cam grinders may not be on the same center... If they're using new blanks, they could put the centerline wherever they wanted.

If they wanted 110 centers. They could just use N/A blanks and grind them 1/2 degree off... I wouldn't assume ALL cams are on stock centers.

Ummm. CL can be moved where ever you like and the only reason for a cam manufacturer to move it on this application is if they assume the buyer does not have adj cam gears..either way ( wether you move the CL with adj cam gears or by grinding) it still is not the zero for our cars unless it is at 109...106....

[RealMcCoy]

Ummm. CL can be moved where ever you like and the only reason for a cam manufacturer to move it on this application is if they assume the buyer does not have adj cam gears..either way ( wether you move the CL with adj cam gears or by grinding) it still is not the zero for our cars unless it is at 109...106....

The centerline is wherever the cam grinder puts it... What came in the car originally is inconsequential and irrelevant. Having four cams, we actually have the luxury of deviating from the manufactured settings... If I buy a cam for an LS motor that's on 108 centers, I'm certainly not going to cry about it not being on the factory 114 degree centers, I'm going install it and degree it to where the cam grinder says it belongs, and hope they know what they are doing...

[oohnoo]

I could be wrong but I think your missing the fact that the cams themselves could be off, that's why you degree them finding the center of the cab lobes, not "ASSUMING" they are cut correctly. I remember Ray saying that BC cams are junk and that he's never had nothing but trouble tuning with them and removes them from any car he builds. I attached the cam card for mine.

Take a look at the BC Cam Card, the note states set to "0" and then tune from there for best result, well 0 is 109.5 in/106.5 ex for us....BC could have reccomended 1XX in/ex but that wouldn't be zero (0) on our cars...Just to clear up any confusion here is the math from the BC Cam card to show the BC cam "0" is the same as our cars ((180+7+31)/2)=109 CL intake ; ((180+1+33)/2)=107 CL ex...

[Italo Grasso]

I could be wrong but I think your missing the fact that the cams themselves could be off, that's why you degree them finding the center of the cab lobes, not "ASSUMING" they are cut correctly. I remember Ray saying that BC cams are junk and that he's never had nothing but trouble tuning with them and removes them from any car he builds. I attached the cam card for mine.

Hey bob, doesn't really matter how off the cams are..if you degree any cam to our zero..109/106 then you have a reference point inwhich you can adv or retard them to what ever you want..right now your cams are degreed to a recommended 110 intake and exhaust you could easily move them back to zero with a little math...degreeing just gives you a refrence point until you tune for best results..my brother is running these BC 272
after we degreed them and they seem to be kicking ass..

[Tigchamp]

Take a look at the BC Cam Card, the note states set to "0" and then tune from there for best result, well 0 is 109.5 in/106.5 ex for us....BC could have reccomended 1XX in/ex but that wouldn't be zero (0) on our cars...Just to clear up any confusion here is the math from the BC Cam card to show the BC cam "0" is the same as our cars ((180+7+31)/2)=109 CL intake ; ((180+1+33)/2)=107 CL ex...

Is this why, when I asked 3SX how I was going to degree my 264/272 cams that I bought from them if they don't supply a cam card. They said just degree them as Stock?
Jeff