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lycoming gear timing?

gladiator68

Active Member
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I'm looking for some insight from you guys who have done this.

I have an older, O-320 D2B that I am in the process of putting back together with an overhauled case, crank and new cylinders.

The gear position timing isn't real clear in the overhaul manual, and not much on YouTube. The timing marks on the crank and mag drive gear are visible, but the cam gear has no visible marks. The only discerning position mark is the alignment dowel. I realize in need to be at TDC on no. 1, but the crank gear has me puzzled.

Thanks in advance for your input!
https://www.smugmug.com/app/photos?imageKey=Lgkr2ZZ

Found the two "0" indicators on cam gear (they were faint and under some varnish) Please delete. Thanks.
 
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Do you have the cam gear on backwards, assuming a two piece cam. If so, the mark(s) will be hidden from you. I had a missing mark somewhere on my 320. I found a pic online and used the visual reference to make a new mark, You can count teeth from the index pin, if you have a visual reference from a cam gear with the mark.

Can';t see pics. Requires password.

Larry
 
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Pretty tough if there are no markings on the cam gear.
What I would do,
For #1 cyl, rotate the cam to a position just beyond intake valve closing into the flat spot just before exhaust valve opening, rock cam back & forth till you are about mid point between. With the crank moved to #1 TDC, insert the Crank idler gear (lt mag drive gear) and see how the marks look compared to the attached drawing. (they may use a different cylinder as reference point but you can work with that).
Good Luck
 

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Figured it out

Thanks guys for the input.

Found the two "0" on the cam gear. They were really faint.

Got the accessory case back on and on to the pushrods.
 
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