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ToyotaChevrolet Big Block Head Bolt Installation Guide (12-Point, 396/402/427/454) — XP984
This guide covers installation of the XOTIC PERFORMANCE™ XP984 12-point head bolt kit for 1965–1990 Chevrolet Big Block engines — 396, 402, 427, and 454 (6.5L–7.4L). Prefer a printable copy? Download the PDF manual.
Two big block head bolt kits — pick the right one. XP984 (this kit) uses 12-point heads. If you're running Dart, late Bowtie, Pro-1 / Pro Topline, or World Products heads and want hex bolts, see the XP980 hex kit and guide. Confirm your heads before ordering.
Why upgrade your big block head bolts
Factory head bolts on a big block Chevy have been through decades of heat cycles, and many have been reused through multiple rebuilds — every reinstall of a stretched bolt means less clamp force than the engine was designed for. Add a stroker crank, a big cam, nitrous, or boost, and cylinder pressures climb well past what tired factory hardware can hold. When the clamping force securing the gasket, head, and block is no longer sufficient, the head gasket lets go.
XOTIC PERFORMANCE™ head bolts are manufactured from our premium XOTIC 7200 steel alloy — far higher tensile strength than standard hardware — and backed by a lifetime warranty. The 12-point head gives you socket clearance in tight spots and a clean look under the valve covers. As with any fastener, the key is accurate preload: the tensile force generated when a bolt is tightened, creating clamp force in the joint. Everything in this guide is in service of achieving equal, accurate preload across all 32 bolts.
What's in the XP984 kit
- 32 × 12-point head bolts (XOTIC 7200 alloy)
- 32 × hardened parallel washers
- 1 × socket
- 1 × fastener assembly lubricant
Before you start: verify first
Confirm that part number XP984 is compatible with your application before installing any components. Inspect all package contents for damage and clean as necessary to ensure accurate installation. Report any obvious defects or shipping damage to us before proceeding.
How to install head bolts on a Chevrolet Big Block
- Clean the block threads. Clean the threads in the block prior to installing the bolts to ensure accurate fitment and precise torque readings. A dedicated 7/16"-14 thread chaser (CS314) makes this fast and protects the threads.
- Clean the washers and seats. Using a clean cloth, remove all oil from the washers and from the cylinder head surfaces where the washers sit. Clean, dry seating surfaces are essential for accurate preload.
- Set the gasket and head. Install the head gasket and cylinder head.
- Seat the washers — chamfer up. Place the washers on the cylinder head with the chamfered inner diameter facing upward, toward the bolt head. Inspect for any misalignment.
- Lubricate. Using the supplied fastener assembly lubricant, coat the threads of each head bolt and the underside of each bolt head.
- Hand-tighten. Thread the bolts in as tight as can be made by hand.
- Torque in sequence. Follow the torque stages below in the numbered sequence shown in the manual's torque sequence diagram, then repeat on the second bank.
Big Block Chevy head bolt torque specs
| Stage | Torque |
|---|---|
| 1 | 25 ft-lbs |
| 2 | 45 ft-lbs |
| 3 (final) | 70 ft-lbs |
A common mistake to avoid: when torquing a fastener, do not stop short of the recommended value — continue in one motion until the specified torque is achieved. If you accidentally stop short, loosen the fastener and re-torque. Stopping short and "topping up" produces unequal preload distribution across the bolts and risks joint failure.
Frequently asked questions
What are the torque specs for big block Chevy head bolts?
Three stages, in the numbered sequence: 25 ft-lbs, then 45 ft-lbs, then a final pass at 70 ft-lbs — with the supplied lubricant on the threads and under the bolt heads.
Which engines does the XP984 kit fit?
1965–1990 Chevrolet Big Block 396, 402, 427, and 454. Verify your application and head style before ordering.
12-point (XP984) or hex (XP980)?
Both torque to 70 ft-lbs and use the same 7/16" thread. XP984's 12-point head gives extra socket clearance; XP980's hex head is specified for Dart, Bowtie, Pro-1, and World Products heads. Pick based on your heads and your socket access.
What size thread chaser do I need?
7/16"-14 — the CS314 chaser.
Need help?
For technical support, email support@xotic-performance.com. All XOTIC PERFORMANCE™ fasteners are covered by our limited lifetime warranty. Finished your install? Tag #XOTICPERFORMANCE on Instagram for a chance to be featured.
© 2026 XOTIC PERFORMANCE™. This installation guide is an original copyrighted work of XOTIC PERFORMANCE™. Reproduction, distribution, or use of this content in whole or in part without written permission is prohibited. Doc ref: 2025.10.21 (web edition 2026.08).
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