Dropping an LS into your OBS K1500 and need longtube headers specifically engineered for a 4WD application? Speed Engineering's 1-3/4" LS swap longtube headers are designed specifically for the 1988–1998 K1500 4WD platform — the geometry engineered around the front axle and transfer case clearance that a 2WD header simply won't accommodate. Race version — no air or EGR fittings. Dyno proven to deliver over 25 rear-wheel horsepower over stock manifolds.
Built from 304 natural stainless steel with merge spikes, CNC-machined flanges, and full TIG-welded construction. Standard graphite manifold gaskets included.
⚠️ Important Notes:
- 4WD K1500 applications ONLY — these headers will NOT fit 2WD C1500 trucks under any circumstances
- LS swap applications only — NOT compatible with SBC or BBC engines
- Race version — no air or EGR fittings — not compatible with emissions equipment
- Speed Engineering Y-pipe may require modifications to connect to the factory exhaust
- 4L80E transmission — bellhousing ears may need to be trimmed for proper clearance
Features:
- Full 1-3/4" Primary Tubes with Merge Spikes — Full-diameter flow from cylinder head to collector for maximum exhaust scavenging
- 3" Collector — Optimized for strong low-to-mid RPM torque
- Mandrel Bent Tubing — Consistent tube diameter through every bend; no crimping, no restriction
- CNC Machined Flanges — Precision fit at the cylinder head for a leak-free seal
- 304 Natural Stainless Steel Construction — Corrosion resistant, heat tolerant, and built to last
- Engineered Specifically for 4WD K1500 Applications — Geometry designed to clear front axle and transfer case components
- Race Version — No Air or EGR Fittings
- Longtube Header Design — Maximum scavenging efficiency vs. shorty or mid-length headers
- Standard Graphite Manifold Gaskets Included
- Dyno Proven — 25+ RWHP gain on LS swap applications
- Compatible with 4.8L, 5.3L, 6.0L, 6.2L, LS1, LS2, LS3, LS6, and LSA Engines
- V8 LS Engines Only
Vehicle Applications:
⚠️ 4WD K1500 applications ONLY. Will NOT fit 2WD C1500 trucks.
Chevrolet K1500 Truck (4WD) — LS Swap
- 1988 Chevrolet K1500 Truck (4WD) — LS Swap
- 1989 Chevrolet K1500 Truck (4WD) — LS Swap
- 1990 Chevrolet K1500 Truck (4WD) — LS Swap
- 1991 Chevrolet K1500 Truck (4WD) — LS Swap
- 1992 Chevrolet K1500 Truck (4WD) — LS Swap
- 1993 Chevrolet K1500 Truck (4WD) — LS Swap
- 1994 Chevrolet K1500 Truck (4WD) — LS Swap
- 1995 Chevrolet K1500 Truck (4WD) — LS Swap
- 1996 Chevrolet K1500 Truck (4WD) — LS Swap
- 1997 Chevrolet K1500 Truck (4WD) — LS Swap
- 1998 Chevrolet K1500 Truck (4WD) — LS Swap
GMC K1500 Truck (4WD) — LS Swap
- 1988 GMC K1500 Truck (4WD) — LS Swap
- 1989 GMC K1500 Truck (4WD) — LS Swap
- 1990 GMC K1500 Truck (4WD) — LS Swap
- 1991 GMC K1500 Truck (4WD) — LS Swap
- 1992 GMC K1500 Truck (4WD) — LS Swap
- 1993 GMC K1500 Truck (4WD) — LS Swap
- 1994 GMC K1500 Truck (4WD) — LS Swap
- 1995 GMC K1500 Truck (4WD) — LS Swap
- 1996 GMC K1500 Truck (4WD) — LS Swap
- 1997 GMC K1500 Truck (4WD) — LS Swap
- 1998 GMC K1500 Truck (4WD) — LS Swap
Frequently Asked Questions:
Q: Will these headers fit my 2WD C1500 OBS truck? No. These headers are engineered specifically for 4WD K1500 applications only. They will not fit 2WD C1500 trucks under any circumstances. For 2WD OBS LS swap headers see part 25-1137 (C1500 2WD).
Q: What is the difference between these headers (25-1012) and the 1-7/8" K1500 4WD headers (25-1011)? The primary tube diameter is the key difference. The 1-3/4" headers (25-1012) offer strong broad RPM range performance and are a great choice for most LS K1500 swap builds. The 1-7/8" headers (25-1011) provide a step up in flow for more aggressive builds with supporting modifications.
Q: Do these headers have air or EGR fittings? No. These are a race version and do not include air or EGR fittings. They are not compatible with emissions equipment.
Q: Will the Speed Engineering Y-pipe connect directly to my factory exhaust? The Speed Engineering Y-pipe may require modifications to connect to the factory exhaust on K1500 applications. Verify fitment before finalizing your exhaust system plan.
Q: Will these fit with a 4L80E transmission? These headers may require trimming of the bellhousing ears on 4L80E transmissions for proper clearance.
Q: What LS engines are compatible with these headers? These headers are compatible with GM LS V8 engines including 4.8L, 5.3L, 6.0L, 6.2L, LS1, LS2, LS3, LS6, and LSA.
Q: What material are these headers made from? 304 natural stainless steel with full TIG-welded construction, CNC-machined flanges, and merge spikes.
Q: Are gaskets included? Yes. Standard graphite manifold gaskets are included.
Q: Are these headers street legal? No. These are race-only headers intended for closed-course competition use only. Installation on a street-driven vehicle may violate the Clean Air Act (42 U.S.C. 7522(a)(3)).
⚠️ Race Use Only: This product is manufactured and sold for installation on vehicles used solely for competition. Once installed, the vehicle may not be used, registered, or licensed for use on a public road or highway. Installation on a street-driven vehicle may violate the Clean Air Act 203(a)(3), 42 U.S.C. 7522(a)(3).
