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Properly Adjusting Mechanical Lifters

Discussion in 'T-Bucket Engine and Driveline Articles' started by Mike, May 24, 2008.

  1. Mike

    Mike
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    So many people ask the question - "How do I properly adjust the valve lash for my engine?"

    There are many different methods, but like so many other situations, there are a lot more wrong ways of doing things. So let's look at the right way to do things.

    In order to properly adjust valve lash, we need to make sure that particular lifter is resting on the heel, or base circle of the camshaft. If the lifter is on the opening or closing ramp, then the clearance will not be adjusted correctly.

    When you look at the cam manufacturer's cam card, you will see there is a specified 'hot' lash setting. So how are you supposed to adjust lash on a new camshaft installation, when all the engine components are cool?

    There is a 'ballpark' correction you can use to come up with a cold lash setting.

    Look up the cam manufacturer's hot lash setting, first of all.

    If you are running a cast iron block and cylinder heads, add .002" to the lash setting.

    If you are running a cast iron block and aluminum cylinder heads, subtract .006" from the lash setting.

    If you are running an aluminum block and cylinder heads, subtract .012" from the lash setting.

    Remember, this is a 'ballpark' number, so once you have either run the engine through a good camshaft break-in period, or have brought the engine up to operating temperature, it will be time to go back through and set the valve lash by the manufacturer's original specification.

    Now it is time to explain how to be sure you are setting the lash when the cam lobe and lifter are in the proper relationship - i.e. the lifter resting on the heel of the lobe.

    1. Remove the valve covers from the engine.

    2. Paying attention to the valves on the #1 cylinder, slowly rotate the engine (by hand, if at all possible). When you see the #1 exhaust valve just starting to open, you can adjust the lash on the #1 intake valve.

    3. Using the correct thickness feeler gauge, adjust the clearance between the tip of the rocker arm and the the tip of the valve. Turn the adjuster until the feeler gauge has heavy drag as you move it between the rocker and the valve. If the adjuster has a locking device, then go ahead and lock it down. Then try moving the feeler gauge between the rocker and valve tip again, to make sure locking the adjuster didn't change the lash by a few thousandths.

    4. Once the #1 intake valve lash is set, then rotate then engine until the intake valve opens and just starts to close. You can then adjust the #1 exhaust rocker, using the procedure outlined in Step #3, above.

    5. You can now move to the next cylinder and adjust those valves, using the same procedure.

    There are a couple of methods of running through the valve settings. You can remove the left-side valve cover and adjust all the valves on that side, then move to the other side of the engine and adjust all the valves on that side.

    If your engine has a fully-degreed harmonic balancer, my preferred method will minimize all the necessary engine revolutions.

    Once the valve covers are removed from the engine, rotate the engine until you see the #1 exhaust valve just starting to open. Adjust the lash on the #1 intake valve. Now, paying attention to the degree markings on the balancer, slowly turn the engine 90°. You can then adjust the intake valve on the next cylinder in the firing order. For an engine with a 1-8-4-3-6-5-7-2 firing order, that would be the #8 intake valve. Once that setting is correct, turn the engine another 90° and adjust the #4 intake valve.

    Once you have adjusted all 8 intake valves, then go back to the #1 cylinder. Turn the engine until the #1 intake valve just begins to close from full lift. Adjust the #1 exhaust valve. Turn the engine 90° and set the number 8 exhaust valve. Turn the engine 90° and adjust the number 4 exhaust valve. Keep rotating the engine 90° after each setting, until you have adjusted the #2 exhaust valve and you are finished.

    There is a caveat to this procedure - it will only work on a engine combination with a 90° firing order.

    There is yet another method for running through the settings. I personally find it about as convenient as a poke in the eye with a sharp stick, but you may find it useful. Again, this is for a 90° V-8 engine with a 1-8-4-3-6-5-7-2 firing order.

    Turn the engine until the #1 intake valve is at full lift and adjust the #6 intake valve.
    Turn the engine until the #8 intake valve is at full lift and adjust the #5 intake valve.
    Turn the engine until the #4 intake valve is at full lift and adjust the #7 intake valve.
    Turn the engine until the #3 intake valve is at full lift and adjust the #2 intake valve.
    Turn the engine until the #6 intake valve is at full lift and adjust the #1 intake valve.
    Turn the engine until the #5 intake valve is at full lift and adjust the #8 intake valve.
    Turn the engine until the #7 intake valve is at full lift and adjust the #4 intake valve.
    Turn the engine until the #2 intake valve is at full lift and adjust the #3 intake valve.

    Now, turn the engine until the #1 exhaust valve is at full lift and adjust the #6 exhaust valve.
    Turn the engine until the #8 exhaust valve is at full lift and adjust the #5 exhaust valve.
    Turn the engine until the #4 exhaust valve is at full lift and adjust the #7 exhaust valve.
    Turn the engine until the #3 exhaust valve is at full lift and adjust the #2 exhaust valve.
    Turn the engine until the #6 exhaust valve is at full lift and adjust the #1 exhaust valve.
    Turn the engine until the #5 exhaust valve is at full lift and adjust the #8 exhaust valve.
    Turn the engine until the #7 exhaust valve is at full lift and adjust the #4 exhaust valve.
    Turn the engine until the #2 exhaust valve is at full lift and adjust the #3 exhaust valve.

    Whatever method you use is entirely up to you. But if you always remember the simple formula of Exhaust Open / Intake Close, you will be able to ensure the opposite lifter is on the heel of the camshaft and that your adjustment will be made at the proper place.
     






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