--- title: Blueprint Engines SBC Intake Manifold Bolt Size & Torque Specifications description: Blueprint Engines SBC Intake Manifold Bolt Size & Torque Specifications | Small Block Chevy Guide --- [Skip to content](https://knowledgebase.blueprintengines.com/knowledge/blueprint-engines-sbc-intake-manifold-bolt-size-torque-specifications#main-content) English Show submenu for translations ![IN CRATE ENGINES..png\]](https://knowledgebase.blueprintengines.com/hs-fs/hubfs/IN%20CRATE%20ENGINES..png?height=40&name=IN%20CRATE%20ENGINES..png) Open main navigation Close main navigation - English Show submenu for translations - Go to www.blueprintengines.com Go to www.blueprintengines.com How can we help you? - There are no suggestions because the search field is empty. 1. [Knowledge Base](https://knowledgebase.blueprintengines.com/knowledge?hsLang=en) 2. [Engine Specs](https://knowledgebase.blueprintengines.com/knowledge/engine-specs?hsLang=en) # Blueprint Engines SBC Intake Manifold Bolt Size & Torque Specifications ## Small Block Chevy (SBC) Intake Manifold Installation Guide This guide covers intake manifold bolt sizes and recommended torque specifications for Blueprint Engines Small Block Chevy applications, including 305, 327, 350, 383, and 400-based SBC engines. ### Identifying Your Cylinder Heads Before installing an intake manifold, determine whether your engine uses pre-Vortec or Vortec cylinder heads. ### Pre-Vortec SBC Heads - Traditional 12-bolt intake manifold bolt pattern - Common on most SBC engines produced before 1996 - Uses angled intake manifold bolts ### Vortec SBC Heads - 8-bolt intake manifold bolt pattern - Found on Vortec-style SBC applications - Uses a unique intake manifold design and bolt pattern - Requires Vortec-specific intake manifolds and gaskets --- ### Intake Manifold Bolt Specifications | Cylinder Head Type | Bolt Size | Thread Pitch | Typical Length\* | | --- | --- | --- | --- | | Pre-Vortec SBC | 3/8"-16 | Coarse Thread | 1.00"-1.25" | | Vortec SBC | 5/16"-18 | Coarse Thread | 1.00"-1.25" | ### \*Bolt length may vary depending on intake manifold flange thickness, spacers, brackets, and accessories. --- ### Torque Specifications Pre-Vortec SBC Intake Manifold **Bolt Size:** 3/8"-16 **Final Torque Specification:** 25 ft-lbs ### Recommended 3-Step Torque Procedure 1. First Pass: 10 ft-lbs 1. Second Pass: 18 ft-lbs 2. Final Pass: 25 ft-lbs ### Torque Pattern ### Tighten bolts in a crisscross sequence beginning at the center of the intake manifold and working outward toward the ends. --- ### Vortec SBC Intake Manifold **Bolt Size:** 5/16"-18 **Final Torque Specification:** 18 ft-lbs ### Recommended 3-Step Torque Procedure 1. First Pass: 9 ft-lbs 2. Second Pass: 15ft-lbs 3. Final Pass: 18 ft-lbs ### Torque Pattern ### Tighten bolts in a crisscross sequence beginning at the center of the intake manifold and working outward toward the ends. --- ### Installation Recommendations To ensure proper sealing and long-term reliability: - Verify the intake manifold is compatible with the cylinder heads being used. - Clean all gasket surfaces thoroughly before installation. - Inspect intake bolt holes for damaged or contaminated threads. - Apply thread sealant on any fasteners that enter coolant passages. - Follow the intake manifold manufacturer's instructions when applicable. - Torque all bolts using a calibrated torque wrench. - Complete tightening in multiple stages following the proper sequence. - Reinspect the engine after initial startup and heat cycling. --- ### Common SBC Applications | Engine Family | Cylinder Head Type | Bolt Size | Final Torque | | --- | --- | --- | --- | | 305 SBC | Pre-Vortec | 3/8"-16 | 25 ft-lbs | | 327 SBC | Pre-Vortec | 3/8"-16 | 25 ft-lbs | | 350 SBC | Pre-Vortec | 3/8"-16 | 25 ft-lbs | | 383 SBC | Pre-Vortec | 3/8"-16 | 25 ft-lbs | | 400 SBC | Pre-Vortec | 3/8"-16 | 25 ft-lbs | | Vortec SBC Engines | Vortec | 5/16"-18 | 18 ft-lbs | --- ### Common Installation Mistakes ### Mixing Vortec and Pre-Vortec Components ### Vortec cylinder heads require a dedicated Vortec intake manifold. Traditional SBC manifolds will not properly fit Vortec heads. ### Over-Tightening Fasteners ### Excessive torque can damage threads, distort sealing surfaces, and cause gasket failure. ### Incorrect Torque Sequence ### Random tightening can lead to uneven gasket compression and sealing problems. ### Failing to Use Thread Sealant ### Some intake manifold bolts may enter coolant passages and require thread sealant to prevent leaks. --- ### Quick Reference | Cylinder Head Type | Bolt Size | Torque Specification | | --- | --- | --- | | Pre-Vortec SBC | 3/8"-16 | 25 ft-lbs | | Vortec SBC | 5/16"-18 | 18 ft-lbs | ### Pre-Vortec Torque Steps - 10 ft-lbs - 18 ft-lbs - 25 ft-lbs ### Vortec Torque Steps - First Pass: 9 ft-lbs - Second Pass: 15ft-lbs - Final Pass: 18 ft-lbs  Technical Support Note For Blueprint Engines assembled long blocks and base engines, intake manifold installation torque values should be followed exactly as listed above. Over-tightening intake manifold bolts, especially on Vortec cylinder heads, can cause gasket failure, vacuum leaks, coolant leaks, or damage to cylinder head threads. **Quick Reference:** - **Pre-Vortec SBC Intake Bolts:** 3/8"-16 → **25 ft-lbs** - **Vortec SBC Intake Bolts:** 5/16"-18 → **11 ft-lbs** **Blueprint Engines Tech Tip:** If replacing an intake manifold on any SBC engine, verify whether the cylinder heads are Vortec or pre-Vortec before selecting gaskets, bolts, and torque specifications. 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