Need firing order for a vortec engine in a 1998 Chev C2500 truck

firing orders and rotation are found on the chev web site
go google and type in firing order for chev engines and get the right order for your engine type

The distributor cap will have a "1" stamped on the top to indicate CYLINDER 1, and will have an arrow indicating direction of rotor rotation.
There will be a sticker affixed to the inside of your engine compartment, listing your correct FIRING ORDER.

could be intake

I am going by the '99-'06 Full size truck Chilton's Manual. The firing order should be the same. It is 1-6-5-4-3-2 on the v-6 engine. 1,3,5 are on the driver's side from grill to firewall and 2,4,6, are on the passenger's side from grill to firewall(this is in the heads). From the boot coming off the main coil(the only one not going to a spark plug) clockwise the firing order on the distributor is 5-1-3-2-4-6. Also make sure the plugs are gapped at .060 in. Hope this helps.

this should be the cyliner order and firing order for it.

back of engine

5 6
3 4
1 2

front of engine

the firing order is 1-6-5-4-3-2

Have you changed the plugs, if any are fouled out or if any are worn, it takes more to fire it under load and may be spark knocking because one of the plugs can't fire off all the gas and cause it to skip or idle rough.

looking from the top front.

go to link for illustration and firing order. please rate my help.

http://autorepair.about.com/library/firing_orders/bl-fo-6477.htm

2.4L Engine
Firing order: 1-3-4-2
Distributorless Ignition System


3.0L Engine

Firing order: 1-2-3-4-5-6


3.3L & 3.8L Engines

Firing order: 1-2-3-4-5-6
Distributorless Ignition System

Vortecs are a little different that old school small blocks, grab a Haynes or Chiltons, the cross patterns and specs are simply diagramed. Vortec, as any really, start with 25# then 45# and then final torque which I believe is around 70-75# but to be sure verify with the manual. AutoZones, Murry's, Adavance auto all carry the books, Cheap insurance.
Dan