If the engine is stock, I'd set the initial timing at 12, make sure the timing mark starts to move when you rev the engine off idle, and watch it advance up to somewhere in the 30 - 35 degree range when it stops. Do this with the vacuum advance disconnected. Then with the timing set at 12 with the engine at idle, hook up the vacuum line to the distributor and see that the timing now shows somewhere in the high 20's to low 30's of timing.
How do you set distubitor timing on pontiac 455?
According to Chilton's 1971 455 is 12btdc, but there should be a decal under the hood or even on the engine itself that would list this info.
the gap on the distributor points is .016, the timing is advanced 4 degrees and the spark plug gap is .030
Should be 12 degrees before top dead center
Should be 12 degrees before top dead center
No, they are completely different.
Did a lot of timing chain jobs on the Pontiacs back in the day, don't remember any of them bending valves.
No, they are not the same engine. The Oldsmobile 455 had a bore and stroke of: 4.126 X 4.25 The Pontiac 455 had a bore and stroke of: 4.152 X 4.21
Sure it will. Pontiac used the same block for all of it's 326 to 455 engines.
Answer Anonymously What is the diagram and firing order for a 76 Pontiac trans am 455 engine?
That depends on what type of distributor/ignition you are running. Point style, good rule of thumb is .035. HEI is usually .045.
Same block, should fir right in