I just went through this on my truck and this is what I was told to do. Chevy does not mark the cap. 1) remove distributor cap, 2) locate number one cylinder and remove spark plug, 3) place finger or compression guage, or whistler etc, over spark plug opening 4) rotate engine until air is blowing out of the plug opening 5) rotor should be pointing to where the number one spot should be on the cap 6) mark the cap where the rotor is pointing this should be number one. Make notes somewhere so this does not happen again.
The marked # 1 position on the distributor cap faces to the FRONT
The marked # 1 position on the distributor cap faces to the FRONT / CENTER
the one inline with the coil in front to the left
Mark your number one spark plug wire where it attaches to the cap ( i use white fingernail polish for marking parts ). Take your new distributor cap out of the box and mark it where you would put the number 1 spark plug cable on it. Then unplug the #1 spark plug wire and the coil wire ( the one in the middle ). Use your finger or carefully use a screwdriver to unpop the two metal clamps that hold the cap down. Since you are replacing your cap you should also replace the rotor, if you have a new one do that now. Plug the #1 spark plug wire and coil wire into the new cap and put it on the distriburtor. Pull off the other spark plug wires and plug them into the new cap , one at a time, in the same place where they were on the original cap.
No-1 wire goes on the distribitor cap in the 7: o clock position clock wise when standing in front of your vehicle. 18436572
The number #1 plug is the forward-most plug on the left (driver's) side. Trace that wire back to the cap and you've got your answer.
get a book Run your spark plug wire from the #1 plug to the #1 lug on the distributor cap. Then follow the rest of the firing order going clockwise around the cap.
The distributor cap should have the number 1 marked on it. The distributor cap is installed with the # 1 position facing the engine , slightly towards the drivers side of the engine
A good quality cap will have a #1 mark on it. #1 cylinder is front driver side.
With hood open, standing on the passenger side, #1 on the distributor cap would be at the 10 O'clock position.
Depending on maker, it should have a number 1 raised letter on the cap
take number 1 spark plug out and bring that piston to top dead center. Then take distributor cap off. Locate which tower the rotor is pointing to on the cap. That will be the number 1 plug wire. Then just follow the firing order. The rotor should turn clockwise.