Top dead center (TDC) is when the number 1 piston is at the very top of it's stroke on it's power (firing) stroke. This holds true for ALL internal combustion piston engines. If you remove the driver side valve cover, the second valve from the front is the intake valve on a small block Chevy, including the 305. Slowly rotate the engine by hand. When the intake valve closes, keep turning the engine until the timing mark lines up at zero. When it does, you are at top dead center.
The typical timing for a 1985 Chevy 454 is 8 degrees before top dead center. The vacuum line removed from the distributor and plugged. The engine warm and idling at 700 rpm.
what engine do you have in your impala?
Bottom right of the water pump. Dead center of the engine in the front.
Dead center on the front of the engine. Probably has a big fan attached to it.
6 to 8 degrees before top dead center.
0 TDC / Top dead center.
The 0 part is the degrees at which it is set. TDC stands for top dead center. Your engine times at 0 degrees at top dead center.
6 to 8 degrees before top dead center. STOCK ENGINE
8 degrees before top dead center.
Top dead center on an engine is defined as when the piston is farthest from the crankshaft. Bottom dead center is when the piston is closest to the crankshaft on the engine.
with a timing light, assuming this is an older engine that still uses a distributor.
6 to 8 degrees BTDC / Before top dead center. with vacuum advance pluged.