Back side of ignition cylinder rotates totally all the way around.is that suppose to happen

IT IS DAMAGED
nor do you know all things the thief damaged,
tow it to a shop get the shop to fix It and back charge the Insurance company for vandalize . \<< gee even ask them first what to do .???
we can't see damage in a text box all over car
It will not happen. so get the car repair by hands on techs in a real shop.

Check to see that the cylinders are exactly the same.
Try replacing and removing the original.

The ignition lock cylinder tumblers get in a bind all the time on GM vehicles. It probably has little to do with inseting the wrong key. Try inserting the correct key and "jiggle" the key in the lock. You may have to jiggle it up and down and rotate (or try to rotate) the lock cylinder forward and backward. It will probably work just fine if you can wiggle it with just the right combination. If not, you may have a damaged lock cylinder and you will have to replace it. - most likely nothing you did....I change at least two or three of these things every week...VERY COMMON.

REMOVAL

1. Disable SIR system. (Refer to "SIR Disable/Enable Procedure (For Frontal and Curtain Inflators)".
2. Disconnect negative battery cable.
3. Remove lock cylinder bezel from steering column shroud by carefully prying with thin blade screwdriver.
4. Remove shroud fasteners and remove steering column upper and lower shroud panels.
5. Insert key into ignition lock cylinder and rotate to RUN position. Then rotate ignition cylinder back to ACC position.
6. Depress locking button on side of ignition module assembly with a thin pick-type tool. Slide lock cylinder assembly from ignition module.

INSTALLATION

IMPORTANT: Actuator blade within ignition module housing must be in ACC position to install lock cylinder assembly. If rotated, replace it to ACC position, using needle nose pliers.

1. Insert key into ignition lock cylinder and install into ignition module.
2. Install steering column upper and lower shrouds and shroud fasteners.
3. Install lock cylinder bezel.
4. Connect negative battery cable.
5. Enable the SIR system. (Refer to "SIR Disable/Enable Procedure (For Frontal and Curtain Inflators)".

Hello quintilla.
Cylinder #1 is supposed to be pointing directly to the right side of the vehicle and in a clockwise rotation from there 6,5,4,3,2.
Cylinders on the left from front are 1,3,5 and the right 2,4,6.
Hope this helps you out.

Its usually NOT the lock cylinder on the 470s, its usually the housing. The cylinder is on the dash and points towards the engine. Behind the plastic dash panel (once removed) you will see it in fact sticks in an aluminum tube that goes down 2 or 3 inches, then makes 2 turns, left to attatch to the steering column, and right to attatch to the actual ignition switch. The gear and rod assembly that the cylinder attatches to that allows it to rotate the switch usually shatters in the middle and the key starts freewheeling because there is no longer any attatchment to any of the gears or springs or click points that youd usually feel as the rotational resistance. UNFORTUNATELY this is not a 5 minute job (If it was, cars would be a breeze to steal!). Youll need at least a lock cylinder housing (dealer stock em, they break all the tyme), and IF your cylinder is undamaged, change the housing (it bolts to the steering column and extends from column towards center console area where the ignition SWITCH is actually located). If your cylinder is damaged or the housing is so shredded you cant remove the lock cylinder by normal means...then youll also need the cylinder...and it will have to be recoded to the vehicle so the anti theft will allow the new keys/cylinder to start the car. If your old cylinder and keys are intact, then transfer them to the new housing and car wont even know it happened and should start up and work as normal. Some can be removed intact, some cant...depends on how yours broke.

It's like a phone number. 1-843-6572 Clockwise rotation of distributor. Number one should be indicated on the dist. cap.cylinders are pass side 1357, drivers side 2468
If #1 is not printed on the cap it is around the 5:30-6:00 position. Unless you are refering to the primary ignition wiring then you can just hop on Autozone and get the wiring diagram from them for free.

the ignition switch is the electrical part behind the lock cylinder where the key goes in.

Ignition Switch Lock Cylinder
Lock Cylinder Functional
Removal

1. The following procedure applies to vehicles that have a functional ignition switch lock cylinder (11582) and keys. If the key numbers are known, the correct key can be made. Disconnect the battery ground cable (14301). For additional information, refer to Section 14-01 .
   

1. Turn the ignition switch lock cylinder to the RUN position.
   

1. Place a 3.17-mm (1/8-inch) diameter wire pin or small drift punch in the hole in the steering column shroud under the ignition switch lock cylinder. Depress the retaining pin while pulling out on the ignition switch lock cylinder to remove it from the housing of the steering column.
   

Installation

1. Install the ignition switch lock cylinder by turning it to the RUN position and depressing the retaining pin. Insert the ignition switch lock cylinder into the steering column housing. Make sure the ignition switch lock cylinder is fully seated and aligned in the interlocking washer before turning the key to the OFF position. This will permit the retaining pin of the ignition switch lock cylinder to extend into the hole of the steering column.
   

1. Using the key, rotate the ignition switch lock cylinder to make sure of correct mechanical operation in all positions.
   

1. Connect the battery ground cable.
   

-------------------------------------------------------------------------------------
Ignition Switch Removal

1. Disconnect battery ground cable (14301). Refer to Section 14-01 .
   

1. Remove the upper steering column shroud (3530) by removing the four or five self-tapping screws. Remove key release lever (3F527) (if equipped).
   

1. Remove lower steering column shroud.
   

1. Disconnect the ignition switch electrical connector.
   

1. Rotate ignition switch lock cylinder (11582) to the RUN position.
   

1. Remove the two screws retaining ignition switch (11572).
   

1. Disengage the ignition switch from the actuator.
   

Item Part Number Description 1 11572 Ignition Switch 2 — Ignition Switch Lock Cylinder Housing 3 — Slot in Lock/Column Assembly A — (Part of 11572) Pin B — Alignment Mark
Installation
NOTE: A new replacement ignition switch assembly will be set in the RUN position as received.

1. Adjust the ignition switch by sliding the carrier to the ignition switch RUN position.
   

1. Check to make sure that the ignition switch lock cylinder is in the RUN position. The RUN position is achieved by rotating the ignition switch lock cylinder approximately 90 degrees from the LOCK position.
   

1. Install the ignition switch into the actuator. It may be necessary to move the ignition switch slightly back and forth to align the ignition switch mounting holes with the lock cylinder housing threaded holes.
   

1. Install retaining screws. Tighten to 5.6-7.9 Nm (50-69 lb-in).
   

1. Connect electrical connector to ignition switch.
   

1. Connect battery ground cable. Refer to Section 14-01 .
   

1. Check ignition switch for proper function, including START and ACC positions. Also, make certain that the column is in the LOCK position.
   

1. Install upper steering column shroud.
   

1. Install the lower steering column shroud and key release lever (if equipped).