Flywheel with no timing marks

[wilkrod]

Hi all,
Unfortunately, it looks like my flywheel doesn't have any timing marks. I was able to determine TDC with the dial indicator to confirm that the cam lobes position were correct for TDC on compression. I also completely rotated the flywheel cleaning off the rust with a dremel, and brass brush, I didn't see any timing marks at all.
So can anyone suggest how to proceed to establish timing marks? I want to set the static timing at 12 deg. BTDC.
Gearbox is an NG3, motor, and gearbox are Banks about 20 years ago to P.O. I don't even know the circumference of the flywheel.
Regards

[jbcollier]

Someone should be able to provide the diameter of the face next to the ring gear.  Then you can calculate the circumference and divide by 360 and multiply by 12 to get the distance for 12°.

Or, you can buy an electronic angle finder and fasten it to the camshaft pulley.  6° of camshaft rotation = 12° of crankshaft rotation.

[wilkrod]

JB,
Thanks man, what about this , I make a template for the alternator pulley marked off in degrees, and use that to determine the 6 degrees of cam rotation, which as you state equates to 12 degrees of crank rotation.
Regards

[jbcollier]

By "alternator pulley" do you mean the pulley that drives the alternator?  If so, yes.

One caveat, after you have found and marked TDC on the crank pulley or, better, flywheel,  then rotate it through to TDC again, set you cam template to zero and rotate forward to 12°.  You can't rotate backwards or the slack in the timing chain will give you a false reading.  Do it multiple times to make sure it is indicating consistently.  Then mark the flywheel and you can use that mark with a timing light.

[BDA]

If you can't find the diameter of the flywheel, maybe you could tape a ribbon on the flywheel and rotate the motor. Mark where the ribbon began and measure that length. Divide by that length by 360, multiply that result by 12 to get the distance from TDC. Mark TDC  position and the 12 BTDC. That may or may not be easier for you but it's at least another option.

I wouldn't disparage the ability to use a timing light because being able to see what the ignition is doing while it's running is useful but remember the 12 BTDC timing is to be taken statically.

[wilkrod]

So, wrapping up the saga, I was able to consistently establish TDC, so then placed a temporary mark on the flywheel. Then using my degree wheel, was able to consistently establish 12 deg. BTDC, placed a temporary mark on the flywheel. Repeated for 20 deg. BTDC, and 30 deg. BTDC. I then went thru the entire drill from scratch, always turning the motor clockwise. All my temporary marks lined up withing 1 deg. My conclusion is that using the cams to determine timing can be very accurate, rembering that the cams rotate twice per crank revolution. I now have permanent, known accurate timing marks on the flywheel. So place the motor at 12 Deg. BTDC, and installed the 123 Distributor. All good, moving on.
Thanks to everyone for their great input.
Regards

[BDA]

... My conclusion is that using the cams to determine timing can be very accurate...

Yes! That had better be true or you're in big trouble!!! 

Your solution was much easier than mine! Good job!