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Old 10-17-2009, 12:37 AM
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Your guys are gonna love this.

Alright before I say anything, i take partial blame for this because i should have done way more research then just trust what the tuner shop said.

Well as you all know i got my engine rebuilt and my whole top end is skunk 2.
Camshafts are the Pro series 1, high comp valve, Pro series cam gears and the valves and retainers. Now what the machine shop who was putting my engine together decided not to clarify to me was about the degreeing of the camshafts. So they just kept them at 0. This was a very big mistake. My engine is now back into my car. I want to know if it is hard or even possible to degree the camshafts with the engine still in the car? I wont be the one doing it but i just want to get an idea of what im looking at. Any ideas would be helpful.
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Old 10-17-2009, 01:00 AM
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Re: Your guys are gonna love this.

Here's some info about that i found on skunk2's site:HOW TO DEGREE CAMSHAFTS OVERVIEW

One of the keys to making power is to properly set camshaft timing; in other words, when valves open and close in relationship to the position of the piston and crankshaft is critical to the performance of the engine. The process of properly setting the camshaft position is referred to as “Degreeing the Cam”. Many beginner tuners mistakenly believe that to degree cams means setting the cam gears at a certain position such as “+1 intake & -2 exhaust”. Though this information may be useful at times, these settings may not be accurate on all motors. For example when the deck of a head or block
is machined, it will retard the cam timing. So the cam gear setting method may only apply to engines using the same type of cam gears with exact same head and block heights; and this also assumes that the given cam gear settings are the correct location for the cams. The most accurate way to set camshaft position is to properly “degree the cams”; this way you can be sure the cams are in the right position regardless of engine variations, deck heights, and cam gear marks. The method we are
introducing is a simple method for setting cam positions using peak lift measurements. Cam degreeing can also be used to check valve opening and closing positions, durations at various lifts, and peak lift measurements.

Step 1: Install a Degree Wheel onto the end of the
crankshaft, and bolt a pointer onto the block. The pointer
can be a sharpened piece of welding rod or coat hanger
that can be bent to change the position of the pointer.
Rotate the crankshaft to TDC, you can use a dial indicator
inserted down the spark plug hole or the piston stop
method; the piston stop method is more accurate. When
the crankshaft is at TDC, move the pointer so it points to
TDC / 0 degree on the degree wheel.
Step 2: Set-Up dial indicator with the tip on the retainer,
not the rocker arm. To get an accurate reading, It is
important to make sure that the axis of the indicator is
parallel with the axis of the valve. Make sure the rocker is
on the base circle of the camshaft, in other words, make
sure the valve is completely closed, and zero out the dial
indicator. We recommend that you degree the cam with
the lash set at 0.000.”
Step 3: Rotate the crankshaft. When the cam starts to
open the valve, the dial indicator will show the amount
of valve lift. Rotate the crankshaft and stop when the
pointer is pointing at the specified peak lift/center line
position. Loosen the cam gear bolts and rotate the
camshaft until the indicator is showing that the cam is at
peak lift. Tighten the cam gear bolts. Rotate the engine
two more rotations, stopping when the dial indicator
reaches peak lift, look down at the degree wheel to
make sure the position of the crankshaft is in the correct
location. If not, repeat step 3.
Step 4: Move the dial indicator to the other side of the
head, and repeat steps 2 and 3. When peak lift positions
of both the intake and exhaust cams are set in the proper
locations, the cams are considered to be degreed in.
Helpful Tip 1: When degreeing a camshaft, make sure
that you rotate the crankshaft in the direction the
engine normally runs. If you over shoot the position the
crankshaft is supposed to be in, do not rotate the engine
backwards, it will throw off your numbers because the
tensioner only works properly in one direction.
Helpful Tip 2: If you are having a hard time finding
the centerline because the cam dwells at peak lift, you
can take a reading of the degree wheel when the cam
reaches max lift less 0.003” before and after peak lift.
The middle of those two positions will be the centerline.







CAM TIMING EVENTS AND 4-STROKE ENGINE OPERATION



Cam Timing, or rather when valves open and close in relation to piston and crank position, is critical to making power. The graph above and the explanation below are an attempt to explain what goes on inside a four-stroke engine, define key terms used when describing cam set-up, and help you better understand the importance of proper cam timing.

1: Piston is at the top of the bore or Top Dead Center (TDC) and both valves are closed. Ignition occurred about 20o-40o before. The piston is being pushed down by the combustion pressure.

2: By 90o after top dead center (ATDC) the cylinder pressure is already starting to decrease and the exhaust valve can begin to open safely before the piston reaches its lowest point or Bottom Dead Center (BDC). The combustion cylinder pressure pushes the burnt fuel mixture/exhaust gases
out the exhaust port.

3: The piston then changes direction after it reaches BDC and begins to help push out the remaining exhaust gases. It is important for the valve to open early enough so the exhaust valve is nearly wide open when the exhaust stroke begins. This reduces the resistance, known as pumping losses, caused by the piston trying to push against the exhaust pressure. Opening the valve earlier will give the engine more time to blow down the exhaust pressure.

4: The exhaust valve is at its maximum opening or peak lift. This is the exhaust centerline position, or rather how many degrees peak lift occurs before top dead center (BTDC). It is important that the peak exhaust lift occurs when the piston is near its maximum velocity on the exhaust stroke to reduce pumping losses.

5: Before the exhaust stroke is complete and the piston reaches TDC, the intake valve begins to open as the exhaust valve continues to close. The exhaust gases traveling out the exhaust port create a suction that helps to draw in the intake charge. This phenomenon is commonly referred to as “scavenging”. When to open the valve is critical because it will determine how much the valve is open when the piston is at maximum velocity on the intake stroke; thus increasing volumetric efficiency (VE).

6: As the piston reaches TDC, both the intake and the exhaust valves are open. The period of time between #5 and #7 is commonly referred to as the overlap period. On low rpm engines the overlap period lasts around 20o-30o. On high rpm race engines overlap may be as long a 50o - 100o.
This much overlap causes the engine to run rough, and the intake charge to go right out the exhaust ports at low speeds.

7: As the piston is moving downward, the exhaust valve closes shut. The later the valve is closed may help with high rpm performance, but will result in poor low rpm operation and emissions.

8: The intake valve reaches its maximum opening or peak lift. This is the intake centerline position, or rather how many degrees peak lift occurs after top dead center (ATDC). It is important for the centerline to be near peak piston velocity on the intake stroke in order to optimize cylinder filling.

9: The piston reaches BDC and begins to travel upward. Notice that the intake valve is still open. Even though the piston is pushing upwards, the inertia generated by the speed and mass of the air/fuel causes the mixture to continue to rush in and fill the cylinder. This phenomenon is called
a “supercharging” effect and is the reason why some naturally aspirated engines can even fill the cylinder up to 130% of its volume.

10: The intake valve closes shut before the piston reaches maximum velocity on the compression stroke. When the intake valve is closed ultimately determines the optimum operating rpm range and also the dynamic compression ratio of the engine. Closing the valve early results in good low
rpm operation, but limits power output and rpm.
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Old 10-17-2009, 08:04 AM
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Re: Your guys are gonna love this.

^^^REP FoJu. Very imformative post.
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Old 10-17-2009, 11:45 AM
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Re: Your guys are gonna love this.

^Thanx playa!
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Old 10-17-2009, 12:06 PM
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Re: Your guys are gonna love this.

I've had to run through this when my boss swapped a 305 H.O. in his S-15 and cammed it. It's not as work intensive as it sounds.
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