FYREANT

NOTE: This How-To guide is neither endorsed by or property of Corvette Forum or myself in any way/shape/form. All liability stemming from any actions taken in relation to this guide is solely placed upon the end user. (This means you!)

Man.. I really should take a night off.. lol

Tonight we’re going to go over how to degree your camshaft, the easy way, and well, the correct way. Awesome! But what does it mean to degree the cam and why would I care about that?! Well, if you were putting in an aftermarket cam in your C7, wouldn’t it suck to get everything back together and get it to the tuner only to find out on the dyno that the engine wasn’t behaving the way the cam card said it should? Yup. Sure would. So, checking your cam with a cam degree kit is highly recommended to give you the peace of mind that your cam was grinded with the specs indicated on the cam card.

Ok, you sold me. No what do I do? Well, first you are going to need a cam degree kit. The kit that I used is a Comp Cams kit 4942. The only problem is that crank adapter for this does not fit so I had to do some improvising for the degree wheel itself. Either way, once you get your kit and get the wheel mounted properly, you’ll need to install the piston stop strap across the number 1 piston. Make sure that the center stop bolt is not sunk down yet, we’ll get to that. At this point, you’ll also want to bolt the “coat hanger” looking thing to the motor and bend it so it looks like how I have it in the pic. There is no science to this part; you are simply using it as a fixed point of reference for the degree wheel. It will be your “pointer” as you can see below.



Now we are going to put the engine in top dead center. To do this, move your engine clockwise until the dot on the crank gear is pointing up, and the arrow on the cam phaser is pointing down so they are both pointing right at each other. At this point, your number 1 piston should be at the top of the cylinder. You will want to “eyeball” the degree wheel to have the TDC marking straight up and centered. Now, we will need to find –True- TDC. To do that, turn the crank counterclockwise about 15° (of the degree wheel) and now we are going to tighten down the center stop bolt for the piston stop. Finger screw it all the way down until it stops on top of the piston, then lightly tighten the locking nut. You'll see that my piston strap has some washers underneath it because the pistons protrude the block so we don't want to damage them with the stop strap.



Now, make sure there is no play in turning the motor over in the clockwise direction, and the make a note of what the degree mark is at on the wheel. In my case, it was 15°. Now we need to turn the engine over counterclockwise until the piston stops on the stop bolt again. Now make a note of the degrees on the cam wheel. This time mine was 345°. Therefore, that means that my wheel was 15°from TDC one-way, and 15° from TDC the other way as well.

Here you can see my two readings when looking for TDC. 15° and 345°





This means my TDC is right at 0°! How you figure this out is you add the two numbers (the number of degrees FROM TDC) and you divide by 2. Which means that 15° from either of my stop points is my true TDC. If you came up with the numbers of 12° and 18°, you would get 30 / 2, which is 15°. If you move the crank from the 12° to 15° towards TDC, you would go over 3°. Which means your TDC would be at the 3° mark. If this happens, you’ll want to loosen the degree wheel without moving the crank and adjust the degree wheel 3° in the appropriate direction so that when you check it again, your TDC with be right where it should be. Once this has been set, go ahead and remove the number 1 piston stop strap completely, as you’re done with that piece.

Great! We found -true- TDC. Now what? Now you’ll want to install the rest of the kit as seen in the pics. It’s hard to explain the contraption on the top so it’s best to mock how mine looks. The small long black shaft will screw into the end of the dial gauge and then the tip will go on the EDGE of the intake lifter since if you put it into the center the hydraulic lifter you may get incorrect readings. The intake lifter is the SECOND lifter from the front of the engine above cylinder 1. The first lifter is the exhaust, which we will check after doing the intake.





There are two ways to degree the cam. The first is the Centerline method, and the second, and more correct method, is confirming the actual intake and exhaust valve opening and closing events at .050” lift. While the first method is not the most accurate, it can get the job done so we’ll go over it anyway. Both methods require you to have already found true TDC, so make sure you do not continue until you have done this. If you do, all your readings could be totally wrong!

Centerline Method:

For this method, you will start by turning the engine over clockwise. Through the course of turning it over you will see the dial indicator starting to spin when you get to the intake lift. Continue on until the indicator gets all the way up as high as it will go. When you get all the way up as high as it will go, if you keep going past this point it will drop back down as you are past the top point of the lift. What you want to do is when you are at the top point of the lift, set the dial gauge at 0 and tighten it down. Now, you will need to make sure you turn the crank over two full times and then make sure that the indicator goes to EXACTLY 0 at the maximum of the lobe lift. If not, readjust the dial indicator and try again. Once you can turn the crank over and the dial reaches zero at the peak of the lobe lift, you are ready to measure for you intake centerline.

Turn the crank counterclockwise until the lifter has dropped about .050” before maximum lift. Now slowly rotate the engine clockwise until the indicator is .020 before max lift and make note the reading on the degree wheel. Continue past maximum lift until you are back at the .020” point on the other side of the lobe. Now make a note of the reading on the degree wheel again. Now, you will need to add the 2 figures together and divide by 2. This will give you the intake centerline. This number should be within +/- 1° of what it says on your cam card.

In this pic I found my maximum lift and went 20° before it and got the reading of 71.5°



Here I went 20° past my maximum lift and got my degree reading of 152.0°. Adding those together comes up to 223.5° divided by 2 is 111.75°.



If the number you got by measuring is the same as what is on your cam card, your cam is –installed- properly, and you do not need to go any farther if this is the method you are choosing to use. This however does not tell you anything about the actual grind of your cam! This is why we are going to use the better method to degree our cam..

Valve Open/Close Method (the right way):

With the cam on the base circle (the area where there is no lift) set the dial gauge to 0 with enough preload (pressure on it) that the gauge is held firmly but not so much preload that you bind the gauge on full lift. Now we are ready to check the opening and closing measurements on #1 intake lobe. Start by rotating the crank clockwise until the lifter moves up .050”. Record your degree wheel reading. Continue turning clockwise through the maximum lift until you are .050” before the indicator returns to 0. Record your degree wheel reading. They should match the opening and closing specs on your cam spec card that you got from the cam manufacturer. Should you have trouble with getting to .050” for the closing point, you can overshoot it, then turn the crank counterclockwise back to 100, and then go back to turning clockwise again to get to .050”.



Now go repeat the same exact process for your exhaust lobe. I’ll wait.. (insert Jeopardy music here)

Here’s where we figure the rest out. We’ll use my cam specs as an example. My cam card read as follows:

Intake Specs -
Valve Open: 2.7°
Centerline: 113°
Valve Close: 46.4°
Duration: 229.1°

Exhaust Specs –
Valve Open: 63.6°
Centerline: 123°
Valve Close: -5°
Duration: 238.6°

When I degreed my cam, I came up with the below actual specs

Intake Specs –
Valve Open: 2.5°
Valve Close: 46.5°

Exhaust Specs –
Valve Open: 64°
Valve Close: -4.5°

Here’s a pic of the intake valve open degree reading, 2.5°:



And here is the intake close reading 46.5°:



In order to confirm the duration of the intake or exhaust, you have to follow a simple formula.

Intake open degrees + Intake close degrees + 180 = duration.
My cam card indicated my intake duration is 229.1°. Using the true numbers I got from degreeing the cam, I came up with an intake duration of 229.0° which is almost spot on. For Exhaust duration, my cam card indicated I should have 238.6°. Using the true numbers I got from checking, my exhaust duration came out to 239.5°, again which is within 1° of spot on. When doing the exhaust you have to make sure to pay attention to the fact that on my cam card the exhaust close event takes place at NEGATIVE 5°, so when I do my duration formula up top, I have to do 64 – 4.5 + 180 to get my duration.

Now for Intake and Exhaust Centerline. Add the values for intake opening (mine was 2.5) + intake closing (mine was 46.5) + 180. Divide by 2 then subtract intake opening (2.5) for my cam, my intake centerline came out to 111.85° (cam card said 113° so not that far off).

On the exhaust side, the formula is similar, but instead of subtracting the intake opening point, subtract the exhaust closing point. So we add the values for exhaust opening (64.0°) + intake closing (-4.5°) + 180. Divide by 2 then subtract intake opening (-4.5°). For me, my exhaust centerline came out to 124.3° (cam card said 123°, again not that far off.

Now, we will use these numbers to find the LSA, or Lobe Separation Angle. The formula for that is: Intake Centerline + Exhaust Centerline ÷ 2 = LSA

So, 111.85° + 124.3° = 118.075° LSA. My cam card said my LSA was 118.1°, so it was spot on!

As you can see from this method, it’s much better to actually degree the cam to locate the opening and closing points of the intake and exhaust so you can properly confirm all the necessary specs on your cam card. Now you can install your cam with confidence that you know exactly what the numbers are, and when your tuner asks if you confirmed the cam, you can tell them you most certainly did!

Ant

FlatPlaneCrankDreams

You're the man. I hope to one day make use of all your guides.