This method is good for the firing order on all chevy small block v8
engines from 265 cubic inches to 400 cubic inches. This would include
265, 283, 305, 327, 350, 400 cu. in. chevy small block v8 engines.
Let's cover some safety concerns first. If you try to troubleshoot a
mixed up firing order with the engine running, you could be in for a
serious shock,.. literally. You can do it, with certain precautions, but
you really don't need to check the firing order with the engine
running. You definitely don't want to try checking the firing order if
you are wearing any kind of pacemaker or sensitive electromechanical
prosthesis. The voltage coming out of the ignition coil is in the
thousands. Common sense dictates that you wouldn't stick a knife in an
electrical outlet, so you wouldn't want to take chances with being
shocked by the electrical discharge from your classic chevy's ignition
See the diagram:
The firing order, which should be cast into the intake manifold, for
the chevy small block V8 is 1-8-4-3-6-5-7-2. The firing order is the
numerical sequence in which the spark plugs are fired. The insertion
position of each spark plug wire around the circumference of the
distributor cap can be found according to a clock face. The insertion
sequence determines the firing order. The firing order is followed
clockwise around the distributor cap starting from the 6:30 position
with the 6:30 position being the number one cylinder spark plug wire.
On classic chevy small block engines that use ignition breaker points
instead of electronic ignitions, the number one cylinder is the one
immediately clockwise of the small metal sash cover on the distributor
cap. The firing order starts here. There is no sash cover on the
distributor cap for GM HEI electronic ignitions, and the firing order is
the same, but starting at the 5:30 position.
The firing order makes sense if you know how the cylinders are
numbered. The number one cylinder is the front most on the drivers side
and 2 being the front most on the passenger side. From front to back,
the cylinders are odd numbered on the drivers side, and even numbered on
the passenger side.
Additional details HERE
Hope helps (remmeber rated this).