When you say unmarked I assume you are talking about not haviong degree marks on you harmonic balancer. How did that happen?

You can find top dead center by using something like a sperkplug with the insulator removed and a bolt threaded into it such that the bolt acts like a stop for the piston as you GENTLEY rotate the crankshaft untile the piston just kisses the bolt. At that point mark a refererance on the balancer against some reference or mark on the timing chain cover. Then rotate the crankshaft the oposite direction until the piston once again kisses the bolt. Mark the balancer in that position. Half the distance between the two marks is TDC. Set this position to the reference mark you selected or made on the timing chain cover.

For degree increments its best to use a degree wheel (protractor if you are not particulare) fastened to the balancer. Or you can measure the diameter of the balancer multiply by Pi and divide by 360 to get the number of inches per degree.

Good luck

John Roncallo