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On the front of the timing chain cover, drivers side towards the top of the harmonic balancer.
There is a mark on the timing chain cover behind the harmonic balancer(behind the crank pulley). The harmonic balancer also has a slot cut in it so that you can line the crank up with the mark on the timing cover. The mark on the timing cover should sit at the 2 o'clock position or the 12 o'clock position. My 96 Chevy 305 is at the 2 o'clock position.
To adjust the timing on a 1992 Chevy 305, first ensure the engine is at operating temperature. Locate the timing mark on the harmonic balancer and the timing tab on the engine block. Use a timing light to check the current timing by connecting the light to the number one spark plug wire and pointing it at the timing mark. To adjust, loosen the distributor hold-down bolt and rotate the distributor slightly until you reach the desired timing, then retighten the bolt.
That would be the biggest and widest mark. Are the first mark on it when turning it clockwise to the pointer.
6 or 8 drgee
There is no timing belt on a 305 unless it is an aftermarket belt drive system.
6 degrees BTC
same as a 350
The easiest way is to look at the Harmonic Balancer. The 305 has a wider thicker balancer than the 350. Pus the timing tab on a 305 is located ON the timing cover and the 350 is bolted on the with the cover bolts. Riky9
8 degrees.
6 BTDC
counter clockwise.