Timing pointer error question.
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Timing pointer error question.

  1. #1
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    Default Timing pointer error question.

    If an engine had an inaccurate fixed pointer attached to the block about 6 degrees counter clockwise BTDC then when aligning with the "0" on balancer. This would indicate an erroneous piston position TDC 6 degrees before actual true TDC right? Now if a timing light was used on this erroneous TDC pointer to set 34 degrees BTDC on balancer (locked distributor) using this inaccurate pointer, would the actual advance be 28 degrees advanced or 40 degrees advanced ? Is the inaccurate advanced pointer causing more advance or less advance with timing light ? I'm thinking it would cause 6 degrees more than the 34 degree set with timing light (yikes! ). A friend thought maybe it would be retarded by 6 degrees . I'm not sure. Any opinions on this from experienced mechanics. Yes pointer / balancer will be reset to exact TDC but engine ran very well for a while with this error. Thanks
    Last edited by zombie; 09-28-2013 at 09:16 PM.

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  3. #2
    Some guy obnoxious001's Avatar
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    Sorry about the quality of this photo, but it is an engine that I rebuilt for a good friend of mine 5 years ago. If you look closely, the mark to the left of the white TDC mark on the damper was the original mark, put onto the IMCO cover by the previous engine builder. It is 6 degrees counter clockwise, so using it as an example, if the damper was turned 6 degrees counter clockwise to align with the incorrect mark, instead of being at zero, or TDC, the timing would actually be 6 degrees advanced.

    The previous engine had a small Whipplecharger, with timing set to 34 degrees (according to the old mark), but burned holes in pistons since the actual timing was really 40 degrees.


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    The situation you had is exactly the same as the one I described ! I'm thinking being slightly rich may have saved my motor. It's running 9 psi (8-71 under driven 10%) on 91 octane and with pulley change (2% over driven) pushing 11.4 psi on AV gas. I ran about 20 gals each set up. If anything bad was going to happen it probably would have. Close call! I've set it back to accurate TDC at 34 degrees. Thanks for informative reply and photo.

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  6. #4
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    Yes it would cause it to add 6 more degreees of advance if I'm understanding you correctly. The only way to truly get it right, is to set it when degreeing your cam. You also could get you a piston stop if the motor is already together and rotate motor backward and forward to locate TDC.

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    Already miss the 310/562 2manymustangs's Avatar
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    Quote Originally Posted by Jspeeddemon View Post
    Yes it would cause it to add 6 more degreees of advance if I'm understanding you correctly. The only way to truly get it right, is to set it when degreeing your cam. You also could get you a piston stop if the motor is already together and rotate motor backward and forward to locate TDC.
    Bazinga!!! finding true TDC is about as basic as any aspect of working on an engine, just do it...

    Anything... something... just find TDC, get it close and stick a screwdriver in the spark plug hole... SOMETHING...

    Speculating about the maybe/if/might be TDC, that kind of stuff drives me nuts... You have to start with SOMETHING known/true...
    Pat Eason, the voice of reason...

  8. #6
    Senior Member SoldHondaBoughtHondo's Avatar
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    Quote Originally Posted by zombie View Post
    The situation you had is exactly the same as the one I described ! I'm thinking being slightly rich may have saved my motor. It's running 9 psi (8-71 under driven 10%) on 91 octane and with pulley change (2% over driven) pushing 11.4 psi on AV gas. I ran about 20 gals each set up. If anything bad was going to happen it probably would have. Close call! I've set it back to accurate TDC at 34 degrees. Thanks for informative reply and photo.
    Just because it didn't grenade doesn't mean you didn't hurt it. Got to ask, was this some kind of afterthought? You woke up in the middle of the night and realized you forgot to check TDC? Now you get to figure out where your cam timing is, even if ya checked it when you installed it and it was right then it's now +6. That's a lot. Mine has enough v/p clearance to run +4. And depending on pistons and a few other things 9lbs of boost 91 octane is kinda close to the edge..jmo

    Zombie=fail.....could be worse, it could have easily been catastrophic fail!
    Last edited by SoldHondaBoughtHondo; 09-30-2013 at 12:08 PM.
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