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LS cylinder heads & intakes compared
Heads and intake decide where an LS makes power. Casting numbers, port type and chamber size, plus intake dyno comparisons.
Heads
| Casting | Port | Chamber (cc) | Intake runner (cc) | Valves | Found on | Notes |
|---|---|---|---|---|---|---|
| 241 | cathedral | 67 | 2.00 / 1.55 | 4.8/5.3 trucks and early LS1 (Speedway); early LS1 C5 Corvette, VT–VY Commodore (Malex) | Baseline casting; flows less than 243/799 stock (Malex) | |
| 243 | cathedral | 64 | LS6 and LS2 (Malex; Wikipedia: LS2 uses 243 castings) | Improved ports vs 241; smaller chambers raise compression on 5.7/6.0 (Malex) | ||
| 799 | cathedral | 65 | 210 | Many aluminum-block 5.3 trucks (Malex); L33 (Wikipedia: "799 heads identical to 243 castings... lacking LS6-spec springs and lightweight valves") | "Truck version of the 243"; nearly identical flow (Malex) | |
| 706 | cathedral | 61 | 1.89 / 1.55 | 4.8/5.3 trucks | Small chambers, good for compression (Speedway). Speedway project: 5.3 + lightly shaved 706 + BTR Truck Norris cam = ~430 hp | |
| 862 | cathedral | 62 | 1.89 / 1.55 | 4.8 and some 5.3 (Speedway) | Slightly larger chamber than 706 (Speedway) | |
| 317 | cathedral | 71 | Iron-block 6.0 trucks (LQ4) | Large chambers lower compression; very common | ||
| 823 | rectangle | 68 | LS3 and L92 (Speedway, Malex) | Much more airflow than cathedral stock; needs rectangle-port intake (Malex) | ||
| 821 | rectangle | 68 | Sources differ: LS3/L92 (Speedway) vs LS9/LSA factory-blown (Malex) |
Intakes
| Intake | Port | Found on | Character | Notes |
|---|---|---|---|---|
| LS1 intake (1997–2000) | cathedral | 1997–2000 LS1 | Composite; replaced by the LS6 design from 2001 | Inferred: source says LS6 manifolds were used on all 2001+ LS1/LS6 Holdener: with the possible exception of the original LS1 intake, stock LS intakes are very good. |
| LS6 intake | cathedral | LS6; all 2001+ LS1 (Wikipedia) | Higher-flowing car intake; common upgrade | LS2 used a similar car-style intake except TrailBlazer SS/Saab 9-7X |
| Truck intake (Gen III/IV cathedral) | cathedral | Vortec 4.8/5.3/6.0 trucks; TrailBlazer SS / Saab 9-7X LS2 | Tall runners, favors low-rpm torque (per Wikipedia re: LS2 truck intake) | Hood clearance is the usual swap issue |
| LS3 intake | rectangle | LS3 | "High-flow intake manifold" (Wikipedia) | Requires rectangle-port heads |
| FAST LSXR / LSXr | cathedral and LS3 (rectangle) versions | Aftermarket | Long-runner modular polymer intake; gains across the curve on street builds; fits stock-intake envelope (LSX Mag, OAC) | 102 mm throttle body |
| Holley Hi-Ram | cathedral, LS3 and LS7 versions | Aftermarket | Short/straight-runner cast intake for 7,000–8,000+ rpm or boost; top-end power, loses midrange; hood clearance required | Available for EFI or carb |
| Holley Mid-Rise | LS (modular) | Aftermarket | Street modular intake, 1,500–6,500 rpm band, 10.44 in tall; may need cowl hood | |
| TrailBlazer SS (TBSS) intake | cathedral | LS2 TrailBlazer SS / Saab 9-7X | Truck-style long-runner; Holdener: early truck, LS2, LS6 and "especially" TBSS intakes all work well | |
| Short-runner intakes (Holley Sniper, Hi-Ram, Pro Flo) | various | Aftermarket | More peak/top-end power, sacrifice torque through much of the curve (Holdener) |
Intake dyno tests
| Test | Engine | Intake | Throttle body | Peak HP | @ RPM | Peak TQ | Notes |
|---|---|---|---|---|---|---|---|
| OAC 5.3 intake test | Cammed 5.3 L33 (799 heads, BTR Red Hot cam.617/.619, 221/24X°, 113 LSA; beehive springs; 1-3/4 in long tubes; Holley HP EFI; 80 lb injectors) | GM truck intake (L33 factory) | 78 mm factory | 456.5 | 6300 | 411.7 | Torque peak at 5,100 and 5,200 rpm |
| OAC 5.3 intake test | Cammed 5.3 L33 (799 heads, BTR Red Hot cam.617/.619, 221/24X°, 113 LSA; beehive springs; 1-3/4 in long tubes; Holley HP EFI; 80 lb injectors) | FAST LSXR (cathedral) | 102 mm FAST Big Mouth | 480.7 | 6400 | 416.7 | +24 hp peak, gains mostly above 5,000 rpm; below that ±1–2 lb-ft |
| LSX Mag LS3 intake test | LS3 street build (~11:1, LSA crank, CNC LS3 heads, COMP LSR cam.617/.624 281/297°, long tubes, Howell EFI, factory PCM) | Stock LS3 (GM Performance) | 102 mm Nick Williams (intake port sized for 92 mm) | 556.3 | 6500 | 497.2 | |
| LSX Mag LS3 intake test | LS3 street build (~11:1, LSA crank, CNC LS3 heads, COMP LSR cam.617/.624 281/297°, long tubes, Howell EFI, factory PCM) | FAST LSXr (LS3) | 102 mm | 566.3 | 6600 | 515.3 | +10 hp / +18.1 lb-ft; fits stock-hood envelope; polymer |
| LSX Mag LS3 intake test | LS3 street build (~11:1, LSA crank, CNC LS3 heads, COMP LSR cam.617/.624 281/297°, long tubes, Howell EFI, factory PCM) | Holley Hi-Ram (300-117) | 102 mm | 605.4 | 7000 | 496.7 | +49.1 hp top end, loses midrange; won't fit under a stock hood |
| LSX Mag LS3 intake test | LS3 street build (~11:1, LSA crank, CNC LS3 heads, COMP LSR cam.617/.624 281/297°, long tubes, Howell EFI, factory PCM) | Holley Mid-Rise (300-135) w/ Hi-Ram top | 102 mm | 555.0 | 6900 | 483.3 | Lost power vs stock on this NA EFI build; designed more for dual-quad/boost; 10.44 in tall |
Sources
- General Motors LS-based small-block engine — Engine table — Wikipedia
- Best LS Heads for 6.0/5.3/4.8 | Cathedral Port Heads vs Rectangular — Speedway Motors
- Decoding LS Head Casting Numbers — Malex Motorsports
- Going FAST(er)! A 5.3L LS Intake Manifold Comparison Test (Richard Holdener) — OnAllCylinders (Summit Racing)
- Dyno Testing Four Popular LS3 Bolt-On Intake Manifolds — LSX Magazine