Caterpillar 
Cummins 
Duramax (Chevy/GMC) 
Ford Power Stroke
Acura
Chrysler
Honda
Jaguar Land Rover
Jeep
Mazda
Mini Cooper
Mitsubishi
Nissan
Polaris
Subaru
Toyota
What drivers say about XOTIC PERFORMANCE™
Head Bolt Kit - 1965-1990 for 6.5L 6.6L 7.0L 7.4L Chevrolet Big Block Mark IV
PART # SKU XP980
Original price
$90.39
-
Original price
$90.39
Original price
$90.39
$90.39
-
$90.39
Current price
$90.39
Availability:
in stock, ready to be shipped
ULTRA STRENGTH
In comparison to standard bolts, our alloy's material characteristics enable much higher tensile strength. For the best fatigue strength, threads are rolled after thermal treatment. A high-quality coating can improve corrosion resistance, reduce friction, and improve overall performance.
EASY INSTALLATION
Installation manual is included with drawn diagrams to ease the installation process. Our head bolts are designed to retain cylinder seal even with today's extremely high-pressure turbo systems.
PREMIUM QUALITY
Black oxide finish protects from wear and tear. Hardened parallel washers allow for uniform load distribution and accurate torque readings.
INSTALL GUIDE
This guide covers installation of the XOTIC PERFORMANCE™ XP980 hex head bolt kit for the 1965–1990 Chevrolet Big Block Mark IV (6.5L, 6.6L, 7.0L, 7.4L). Prefer a printable copy? Download the PDF manual.
Check your cylinder heads. XP980 is specified for Dart iron and aluminum heads, late Bowtie, Pro-1 / Pro Topline, and World Products heads on the Mark IV big block. If you're running different heads, confirm bolt length and seat compatibility with us before ordering.
Why upgrade your big block head bolts
Factory head bolts on a Mark IV big block 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. Bolts are the right call when you want strong clamping with the convenience of pulling a head in the chassis without fighting stud clearance. 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 XP980 kit
- 32 × hex head bolts (XOTIC 7200 alloy)
- 32 × hardened parallel washers
- 1 × socket
- 1 × fastener assembly lubricant
Before you start: verify first
Confirm that part number XP980 is compatible with your application and cylinder heads 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 Mark IV
- Clean the block threads. Clean the threads in the block prior to installing the bolts to ensure proper fitment and accurate torque readings. A dedicated 7/16"-14 thread chaser (CS314) makes this fast and protects the threads.
- Clean the washer seating areas. Clean the washer seating surfaces on the cylinder head with a fast-evaporating solvent such as non-chlorinated brake cleaner to remove oil, grease, and contaminants. A clean surface is essential for achieving proper fastener 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 side 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 the bolt heads.
- Hand-tighten. Thread the bolts in and hand-tighten until snug.
- 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 Mark IV head bolt torque specs
| Stage | Torque |
|---|---|
| 1 | 23 ft-lbs |
| 2 | 46 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 XP980 big block head bolts?
Three stages, in the numbered sequence: 23 ft-lbs, then 46 ft-lbs, then a final pass at 70 ft-lbs — with the supplied lubricant on the threads and under the bolt heads.
Which heads does the XP980 kit fit?
Dart iron and aluminum, late Bowtie, Pro-1 / Pro Topline, and World Products heads on the 1965–1990 Mark IV big block. Confirm your head casting before ordering.
Which way do the washers go?
Chamfered side up, facing the bolt head. The flat side sits against the cylinder head.
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: 2025.10.19 (web edition 2026.08).
PACKAGE CONTENTS
VEHICLE FITMENTS
⚠️ PROP 65 WARNING
CALIFORNIA WARNING: Cancer and Reproductive Harm -www.P65Warnings.ca.gov
