Timing Belt with camshaft 180 degrees off...help!
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This is a discussion on Timing Belt with camshaft 180 degrees off...help! within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; When swapping out my timing belt, I aligned the intake cam of the #2 & #4 cylinders 180 degrees off. ...

  1. #1
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    Nov 2009
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    Denver, CO
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    Unhappy Timing Belt with camshaft 180 degrees off...help!

    When swapping out my timing belt, I aligned the intake cam of the #2 & #4 cylinders 180 degrees off. I only realized this when the car wouldn't start or even stumble after reassembling everything (the timing marks are remarkably similar!). I don't think I bent a valve because nothing binded during assembly and my hand rotations, and nothing banged during my attempted starts.

    So here's my current task:
    ===================
    I need to turn the driver side intake cam 180 degrees without interfering with the other cam and/or the piston.


    Here are my thoughts of how to fix the situation:
    ====================================
    1) Remove the belt with the timing marks as per the normal instructions (the driver side intake will be 180 off).

    2) Allow the driver side exhaust cam to turn about 45 degrees clockwise to a zero lift position (this should happen normally as it is under tension).

    3) Rotate the driver side intake cam 180 degrees in the clockwise direction.

    4) Install the belt as per the normal instructions.


    Rationale:
    =======
    Assumptions: (I will verify this later tonight) Top dead center (TDC) is 90 degrees from the timing mark (i.e., when the timing mark is at 12 o'clock, the TDC mark is at 3 o'clock). This also means when the timing mark is at the 12 o'clock position on the cams, the TDC is at the 1:30 position. Another assumption is that the firing order is 1-3-2-4 (where cylinders 1 and 3 are on the passenger side and 2 and 4 are on the driver side).

    ** The rest of my thoughts are with the timing marks lined up at 12 o'clock as per the instructions. **

    So, I think my thoughts will work because the #2 cylinder should be in the middle of the intake stroke and the #4 cylinder should be in the middle of the exhaust stroke. Therefore, the #2 cylinder intake valve is supposed to be open and the #4 cylinder exhaust valve should be open.

    HOWEVER, since I have the driver side intake cam off by 180 degrees, the current state is that the driver side intake cam is in the zero lift position and the #4 exhaust valve is open.

    By rotating the driver side intake cam in a clockwise direction, the cam should go through about 135 degrees of zero lift, then about 45 degrees during which the #2 intake valve will open. Even with the #4 exhaust valve open, the #4 intake valve should remain closed while I rotate the intake cam 180 degrees.


    BTW, I think it I'm very lucky if/that there was no interference between the valves on the #2 and #4 cylinders. I'll have to run a compression test afterwards to make sure things are still okay.


    Any thoughts or comments are appreciated.

    Just a thought, why wouldn't Subaru stamp the timing marks so the install is done with the engine at top dead center?!?!? This way no elbow grease is required to line up the driver side cams.

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  3. #2
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    Nov 2009
    Location
    Denver, CO
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    It's all good

    As I suspected, TDC for the engine is 90 degrees from the timing mark on the crankshaft (45 degrees on the cams, which are marked by an arrow). I followed the steps outlined in my above post, and the car works perfectly now.

    The driver side cams weren't too tough to line up, but I had to use two 10mm allen wrenches. Once those two were done, everything else fell right into place. Whew!

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