On the T1 Silverado this is one of the easier tune-up jobs. The 5.3L L84 and 6.2L L87 both use coil-on-plug with the coils bolted to the valve covers, so you pull an 8 mm bolt or two, lift the coil, and the plug comes out with a 5/8 in plug socket. The only real challenge is the rear cylinders, where a swivel plug socket and a wobble extension save you from unbolting brackets around the brake booster and A/C lines.
The 2.7L turbo is fewer plugs but tighter work — the cover and harness have to come off and you are reaching down past hot turbo plumbing. The 3.0L Duramax has no spark plugs at all. The single most common mistake on all of these is overtightening: these are M14 plugs in aluminum heads, and people crank them past 15 ft-lb, or they install them with anti-seize and then torque to the dry spec. Install dry, torque with a real torque wrench, and work only on a cold engine.
| Item | Type | |
|---|---|---|
| Socket set, 3/8 in drive 8 mm, 10 mm, 13 mm shallow 6-point Coil bolts (8 mm), engine/air box covers and battery terminal (10 mm), misc brackets. | Required | shop |
| Ratchet, 3/8 in drive Standard plus stubby or 90-tooth low-profile Main driver for coils and plugs; the short ratchet helps at the rear cylinders. | Required | shop |
| Spark plug socket 5/8 in (16 mm) thin-wall magnetic or rubber-insert, 3/8 in drive Removes and installs the plugs without cracking the insulator; check your plug hex if fitting aftermarket plugs. | Required | shop |
| Swivel spark plug socket 5/8 in universal-joint style, 3/8 in drive Best way to reach cylinders 7 and 8 on the V8 without removing accessories. | Recommended | shop |
| Extension set 3 in, 6 in, 10 in plus wobble extensions, 3/8 in drive Reaches down the plug wells and around the brake booster and A/C lines. | Required | shop |
| Universal joint 3/8 in drive Angled access to the rear coil bolts. | Recommended | shop |
| Torque wrench 3/8 in drive, 10-80 ft-lb range Plugs thread into aluminum heads and must not be overtightened. | Required | shop |
| Compressed air or blow gun Shop air or canned air with wand Blows dirt out of the plug wells so nothing drops into the cylinder. | Recommended | shop |
| Spark plug gap tool Coin-style or wire feeler gauge Verify gap on new plugs; do not pry on iridium tips, only check. | Recommended | shop |
| Trim tool set Plastic pry tools Frees engine cover clips and wiring harness retainers, especially on the 2.7L. | Recommended | shop |
| Pick or small screwdriver Hooked pick Releases the coil connector locking tabs without breaking them. | Recommended | shop |
| Spark plugs V8 5.3/6.2: ACDelco 41-162 iridium (8); 2.7L L3B: ACDelco OE iridium (4) — confirm by RPO/VIN The service item; buy the exact plug listed for your engine code. | Parts | shop |
| Dielectric grease Silicone dielectric compound Thin film inside the coil boot so it does not stick or arc. | Consumables | shop |
| Shop rags and brake cleaner Aerosol brake cleaner Clean oil and debris from around the coil bosses before removal. | Consumables | shop |
| Nitrile gloves and safety glasses Hot engine bay, cleaner overspray and debris in the plug wells. | Safety | shop |
| Thread chaser M14 x 1.25 spark plug thread chaser Only if threads are carboned or damaged; not routinely needed. | Recommended | shop |
5.3L L84 and 6.2L L87: eight plugs, 5/8 in (16 mm) plug socket, 8 mm coil bolts, all reachable from the top. 2.7L L3B turbo: four plugs under the plastic cover, still a 5/8 in hex on the OE plug but a thin-wall socket and longer extensions are needed, and the torque spec differs — check it. 3.0L Duramax: diesel, glow plugs only, none of this applies.
| Spark plug (5.3L L84 / 6.2L L87, aluminum head) | 15 ft-lb (20 Nm) |
| Spark plug (2.7L L3B) | verify in the service manual |
| Ignition coil mounting bolts | 89 lb-in (10 Nm) — verify in the service manual |
| Battery negative terminal nut | verify in the service manual (snug, roughly 11 lb-ft) |
The 5/8 in plug socket, 8 mm coil bolts and 15 ft-lb plug torque for the 5.3L L84 and 6.2L L87 are solid; the 2.7L L3B plug torque, exact plug part number for your RPO and the coil bolt torque should be confirmed in the GM service information for your VIN.
A 5/8 in (16 mm) spark plug socket on a 3/8 in drive for the 5.3L and 6.2L V8s, plus an 8 mm socket for the ignition coil bolts. A swivel-type plug socket with a wobble extension makes the rear two cylinders on each bank much easier.
15 ft-lb (20 Nm) into the aluminum cylinder head, installed dry with no anti-seize. Coil bolts are roughly 89 lb-in (10 Nm) — light. Verify both in the service manual for your VIN.
GM's maintenance schedule for the iridium plugs in these trucks is generally around 97,500 miles on the V8s; the 2.7L turbo interval is shorter. Check the maintenance schedule in your owner's manual, and replace earlier if you have misfires or heavy towing use.
No. On the 5.3 and 6.2 all eight plugs come out from the top of the engine bay with the right extensions. On the 2.7L you remove the engine cover and move the harness and heat shielding, but the intake stays on.