How do you degree a cam with the heads on?
10-20-2002, 11:57 AM
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Re: How do you degree a cam with the heads on? YEARS ago I did it commonly on the standard SBC. Dial indicater and magnetic base - Degree wheel of course - take a stock worn out spark plug,knock the ceramic interior out and thread/tap the interior of the old spark plug body to allow you to run a threaded bolt with the nose ground round to act as a stop for the piston to "seat" against. This you may understand will give you the ability to find crank rotation top dead center on number one cylinder (or any) - by rotating gently foreware against the stop - then reverse against the stop while recording the "degree" reading, then adjust the wheel to indicate TDC and procede as normal for the rest of the cam degreeing in process. I used to rig a seperate pointer for the crank TDC from the cam info' so that I could recheck the crank position afterwards so I knew that I was on the money.
<small>[ October 20, 2002, 11:59 AM: Message edited by: P&DZs ]</small>
<small>[ October 20, 2002, 11:59 AM: Message edited by: P&DZs ]</small>
10-20-2002, 08:09 PM
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Re: How do you degree a cam with the heads on? Thats pretty much it.... you have to find Top Dead Center.
Once you find that point...everything else is pretty straight forward.
Need any more info?
John
Once you find that point...everything else is pretty straight forward.
Need any more info?
John
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10-21-2002, 02:22 PM
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Re: How do you degree a cam with the heads on? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">How do you fashion the plug so that you know you're at EXACTLY TDC instead of just below it (if you made the stop too long?) </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That is not how it's done.
P&DZs already posted how it's done above..
You install the stop. Rotate the motor until the piston hits the stop. This will be at a point before TDC.
You then mark that spot on the degree wheel.
Then turn the motor in the opposite direction until it hits the stop again.
Mark that point on the wheel.
Now you will have 2 marks on the wheel.
The center point of those 2 marks is TDC.Rotate the motor to the center spot and reposition the degree wheel to read TDC.
It sounds like you should read up on how to degree a cam. Comp Cams I think has a nice How-to on their website.
Steve
P&DZs already posted how it's done above..
You install the stop. Rotate the motor until the piston hits the stop. This will be at a point before TDC.
You then mark that spot on the degree wheel.
Then turn the motor in the opposite direction until it hits the stop again.
Mark that point on the wheel.
Now you will have 2 marks on the wheel.
The center point of those 2 marks is TDC.Rotate the motor to the center spot and reposition the degree wheel to read TDC.
It sounds like you should read up on how to degree a cam. Comp Cams I think has a nice How-to on their website.
Steve
10-21-2002, 03:17 PM
#9
Re: How do you degree a cam with the heads on? SJH, I know that isn't how you degree the cam wheel. I could easily fashion a sparkplug, thread in a long *** thread and the piston would hit the rounded thread WAY before it was actually at TDC, right? I want to make sure I'm exactly at TDC, am I missing something?
10-21-2002, 03:47 PM
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Re: How do you degree a cam with the heads on? Here, I pulled this from crane cams site:
With the rocker arms removed, screw in the piston stop until it contacts the piston.Turn the engine in the same direction until the piston comes back up and touches the piston stop. Make a note of what degree the pointer is on the degree wheel.
Turn the engine in the opposite direction until the piston comes back up and touches the piston stop. Make a note of what degree the pointer is on the degree wheel. Add these two numbers together then divide them in half.
Example: Let’s say that the stop points are 16° in one direction and 20° in the opposite direction. The total would be 36 degrees. This figure divided in half would be 18 degrees. Therefore 18 degrees from either of your stop points is true top dead center. Now either move the pointer to align with the 18 degree mark on the degree wheel, or carefully loosen the degree wheel (without disturbing the position of the crankshaft) and move the degree wheel to the 18 degree mark, making sure that the piston is still against the stop. Now turn the engine in the opposite direction until the piston comes back up and touches the stop. The pointer should be aligned with the 18 degree mark on the other side of the TDC mark.
If this is correct, then you have found true top dead center. It is best to repeat this to make sure that nothing has moved. If you didn’t get 18°, as per our example, you will need to repeat the procedure until you get the same amount of degrees on both sides of TDC. Remove your piston stop and you are ready to properly degree your cam.
Her's the whole procedure:
http://www.cranecams.com/instruction...ing/degree.htm
With the rocker arms removed, screw in the piston stop until it contacts the piston.Turn the engine in the same direction until the piston comes back up and touches the piston stop. Make a note of what degree the pointer is on the degree wheel.
Turn the engine in the opposite direction until the piston comes back up and touches the piston stop. Make a note of what degree the pointer is on the degree wheel. Add these two numbers together then divide them in half.
Example: Let’s say that the stop points are 16° in one direction and 20° in the opposite direction. The total would be 36 degrees. This figure divided in half would be 18 degrees. Therefore 18 degrees from either of your stop points is true top dead center. Now either move the pointer to align with the 18 degree mark on the degree wheel, or carefully loosen the degree wheel (without disturbing the position of the crankshaft) and move the degree wheel to the 18 degree mark, making sure that the piston is still against the stop. Now turn the engine in the opposite direction until the piston comes back up and touches the stop. The pointer should be aligned with the 18 degree mark on the other side of the TDC mark.
If this is correct, then you have found true top dead center. It is best to repeat this to make sure that nothing has moved. If you didn’t get 18°, as per our example, you will need to repeat the procedure until you get the same amount of degrees on both sides of TDC. Remove your piston stop and you are ready to properly degree your cam.
Her's the whole procedure:
http://www.cranecams.com/instruction...ing/degree.htm
