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How to: Balance Shaft Timing Procedure

Discussion in 'Under the Hood' started by 2000StreetRod, January 25, 2014.

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  1. 2000StreetRod

    2000StreetRod Staff Member Moderator Elite Explorer

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    Background
    The SOHC V6 was installed in 4WD models with a balance shaft and in 2WD vehicles without one (4WD engine shown below).
    BlncShft.jpg
    The balance shaft chain tensioner is rather flimsy and prone to failing sooner than the other improved (2002 and later MYs) timing chain related components. Replacing the entire balance shaft chain tensioner requires removal of the block cradle since the tensioner base retaining bolts are in the vertical position. Some members have successfully replaced just the spring portion of the tensioner by bending the pivot post out of position, sliding off the old spring section, sliding on the new spring section, and then bending back the post. It is unknown how much the stress of bending the post reduces its reliability. Some members have just cut the balance shaft chain rather than remove and reinstall the block cradle to correctly replace the tensioner. There has been much discussion on the forum about the need for a functional balance shaft because of the difficulty associated with chain tensioner replacement or because of the desire to replace a balance shaft equipped engine with an available engine with no balance shaft (or vice versa).

    Below are the comments I posted in 2010 and still think valid:

    "Two types of imbalance associated with the SOHC V6 engine are rotational imbalance and reciprocating imbalance. The crankshaft counter weights reduce rotational imbalance. The balance shaft is used to reduce reciprocating imbalance. That is one reason that the balance shaft rotates much faster than the crankshaft. A symmetrical opposing (flat) engine needs no balance shaft because the reciprocating forces of one piston are offset by those of an opposing piston.

    I remember many years ago as inline four cylinder engine displacement increased from year to year that there was a common belief that two liters was the maximum size possible due to vibration concerns. The industry incorporated balance shafts to exceed the two liter limit. Some engines even had two balance shafts rotating in opposite directions.

    4WD associated components are all rotationally balanced. I suspect that Ford chose to implement the balance shaft for reduced vibration for customer satisfaction rather than increased serviceability. Ford produced millions of V6 engines (OHV and SOHC) with no balance shafts and no associated recall notices due to premature failure. I'm not aware of any technical service bulletins regarding premature crank failure related to the absence of a balance shaft. Some standard shift performance enthusiasts purchase lightened flywheels for reduced rotational mass and increased throttle response. The negative impact is a slightly less smooth idling engine. I think the balance shaft issue is an analagous trade off.

    I would not be concerned about premature crankshaft failure when using an engine with no balance shaft."

    Timing the balance shaft requires no special tools and is not complicated. However, it is difficult to describe without multiple drawings or photos. My 2WD SOHC V6 has no balance shaft so I have no photos of one. However, I have access to the 2005 Mustang SOHC V6 Engine Assembly Instructions which surprisingly (since to my knowledge no 4WD Mustangs were manufactured) has a good description with adequate drawings. The instructions are the main source for this procedure. I also used information from my Haynes Repair Manual and my personal experience gained from forum posts.

    Balance Shaft Timing Procedure

    Rotate crankshaft until the No. 1 piston is at
    top dead center.

    Install the balance shaft. (It is not necessary to remove the balance shaft to replace the chain or time the balance shaft).
    1 Position the balance shaft assembly.
    2 Install the bolts and tighten to 27 Nm (20
    lb-ft).

    BalanceShaft.jpg

    NOTE: Due to the gear ratio between the
    reversal shaft and the balance shaft, up to 7
    complete turns of the balance shaft may be
    required to find the correct position.
    Align the timing marks. The hole (B) in the assembly should be centered between the two marks (A) on the sprocket and the mark on the balance shaft (C) should be aligned with the bottom of the block casting and on the side close to the crankshaft.
    • Install a 4 mm (0.16 in) pin or drill bit to hold the
    shaft in place.

    Timing1.jpg

    Install the balance shaft chain and
    crankshaft sprocket.

    timing2.jpg

    1 Position the balance shaft tensioner with its pin installed.
    2 Install the 2 bolts and tighten to 29 Nm (21
    lb-ft).
    3 Position the balance shaft chain guide,
    install the 2 bolts and tighten to 10 Nm (89
    lb-in).
    • Remove the pin from the tensioner and the alignment pin from the balance shaft sprocket.

    Timing3.jpg
     
    Last edited: January 25, 2014
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  3. carpenter

    carpenter New Member

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    balance shaft 4WD or 2wd

    Although every forum will say that the motor with balance shaft is only available in the 4wd cars. The 4.0 L sohc engine in mine 2004 xlt explorer (2wd),has a balance shaft! with your saying about the mustang throws away the myth of 4wd against 2wd. i had to open the engine for timing chain issues. My best guess is that the engines are going in at random, from the pile of available engines and suitable for a particular model. not throwing in engines without a balance shaft in 4wd's, and lets say 2wd doesn't matter, if nothing else is available.
     
  4. plasticseng

    plasticseng Active Member

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    I know this is an old thread, but can anyone tell me how many leaf springs I should have on the original balance shaft tensioner (2002 Explorer 4.0)? I only found one, even after taking off the cradle, and wonder if I need to keep looking.

    BTW, mine is a 2WD and I got a surprise when I pulled the timing cover and found a balance shaft. The really bad part is that the balance shaft tensioner was the only broken timing component after 257,000 miles.
     
  5. William hunter

    William hunter New Member

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    What do you do if you rotate the engine and still can't get the balance shaft timing marks to align with motor at topdead center
     
  6. 2000StreetRod

    2000StreetRod Staff Member Moderator Elite Explorer

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    Have you rotated the balance shaft up to 7 revolutions and still not achieved alignment as indicated in the first post? Did you make the mistake of removing the balance shaft sprocket?
     
  7. William hunter

    William hunter New Member

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    No but the chain is loose and I've found pieces of link for the chain . Yes I did rotate it more than 7 times with no luck
     
  8. 2000StreetRod

    2000StreetRod Staff Member Moderator Elite Explorer

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    If the balance shaft sprocket retaining bolt has not been loosened then the balance shaft chain has probably slipped. There are gears between the balance shaft sprocket and the balance shaft that are not visible from the front. As I recall the balance shaft rotates faster than the sprocket. That is why it may take up to 7 rotations for the marks to align. If when the marks align the crankshaft is not at TDC then the chain has slipped. To correct the timing the chain must be removed (in your case replaced) and then reinstalled after the crankshaft has been rotated to the piston 1 TDC position.
     
  9. William hunter

    William hunter New Member

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  10. William hunter

    William hunter New Member

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    Thank you no the balance shaft bolts were not loosened and it seems that the the chain has slipped. I do have a new chain so I just bring the engine to tdc and possition the gear and balance shaft mark on the timing marks and install the new chain anything else I should be aware of ?
     
  11. 2000StreetRod

    2000StreetRod Staff Member Moderator Elite Explorer

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    The balance shaft chain tensioner normally fails much sooner than the chain. Do you have a new tensioner? Is the engine out of the vehicle? The complete tensioner assembly can't be replaced without removing the block girdle (upper oil pan). Some forum members have successfully replaced the movable portion of the tensioner without removing the base. The process is mentioned in another thread.
     
  12. William hunter

    William hunter New Member

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    Hi yes I have a new balancer chain and tensioner.the motor is out and on an engine stand the heads are already off as is the lower pan and skirt the plastic parts of the tensioner were in the oil pan
     
  13. the big g

    the big g New Member

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  14. the big g

    the big g New Member

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    Wish i had have see your post while i had the my motor open and out of the car . Have installed new timing chains front and back of motor. That part has all gone well but i had no idea about the timing of the balance shaft. I remember lining up the dots on the sprocket gear but did not pay any attention to the hole on the balance shaft. I think the timing is out because the motor has a strange vibration at higher revs as it goes through the gears. Is there any way of checking this other than exposing the front timing chains. If it is out how can it be corrected without taking the motor out of the car . Look forward to your reply Regards George
     
  15. Tech By Trade

    Tech By Trade Well-Known Member

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    Gotta drop the cradle. Pretty much gotta pull the engine to do that.
     
  16. the big g

    the big g New Member

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    Do you think there might be a posability of some how being able to hold down the spring loaded guides so the chain can be removed.
    then it would be a simple matter of rotating by hand until the timing marks line up.

    Do you have much experience with this motor ?
     
  17. Clarence Oosterhoff

    Clarence Oosterhoff New Member

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    Removing the tensioner does not give enough slack in the chain to retime it. I have mine apart and it did not have a balance shaft chain tensioner from factory and was still in time!
     
  18. Clarence Oosterhoff

    Clarence Oosterhoff New Member

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    Cloyes has an awesome video on YouTube for timing chain replacement
     
  19. donalds

    donalds Elite Explorer

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