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Head Bolt Kit - 1999–2003 4.8L-6.2L Chevrolet Gen III LS (12-Point)
PART # SKU XP988
Original price
£115.00
-
Original price
£115.00
Original price
£115.00
£115.00
-
£115.00
Current price
£115.00
Availability:
In stock
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™ XP988 12-point head bolt kit for 2003-and-earlier Chevrolet Gen III LS engines (4.8L, 5.3L, 6.0L, 6.2L). Prefer a printable copy? Download the PDF manual.
Three early-LS head fastener kits — check the year and the drive style. XP988 (this kit) is a 12-point head bolt kit for 2003-and-earlier Gen III LS engines. XP987 is the same fitment in a hex-drive head bolt kit. For 2004+ Gen III/IV engines — where GM changed to same-length primary bolts — you want the XP981 kit and guide. Confirm your engine before ordering.
Why upgrade your LS head bolts
Factory LS head bolts are torque-to-yield and single-use — once the heads come off, they're done. If you're buying fasteners anyway, this is the moment to step up. Cam swaps, nitrous, and boost all raise cylinder pressures well past what the stock hardware was designed to hold, and 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 drive on this kit gives you a smaller wrenching footprint and better socket engagement in the tight pockets on an LS deck, which matters when you are working in the chassis. Bolts in general are the right call when you want strong clamping with the convenience of pulling a head without fighting stud clearance under the cowl. For maximum clamping on a serious boost build, see our early LS head stud kit (CP887) and guide. Either way, the key is accurate preload: the tensile force generated when a fastener is tightened, creating clamp force in the joint. Everything in this guide is in service of achieving equal, accurate preload across all 30 bolts.
What's in the XP988 kit
- 30 × 12-point head bolts (XOTIC 7200 alloy) — 11mm primary and 8mm secondary
- 30 × hardened parallel washers
- 2 × sockets
- 1 × fastener assembly lubricant
Before you start: verify first
Confirm that part number XP988 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 12-point head bolts on an early LS
- Clean the block threads. Clean the threads in the block prior to installing the bolts to ensure accurate fitment and precise torque readings. Dedicated chasers make this fast: M11 x 2.00 (CS324) for the primary holes and M8 x 1.25 (CS317) for the small ones.
- Clean the washer seats. Clean the washer seating areas on the cylinder head with a fast-evaporating solvent such as non-chlorinated brake cleaner to remove oil and contaminants. 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 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.
Early LS 12-point head bolt torque specs
11mm bolts (positions 1–10)
| Stage | Torque |
|---|---|
| 1 | 25 ft-lbs |
| 2 | 50 ft-lbs |
| 3 (final) | 75 ft-lbs |
8mm bolts (positions 11–15)
| Stage | Torque |
|---|---|
| Final | 30 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 XP988 12-point LS head bolts?
The 11mm bolts (positions 1–10) go to 25, then 50, then 75 ft-lbs in sequence. The 8mm bolts (positions 11–15) torque to 30 ft-lbs. Repeat the sequence on the second bank.
Which LS engines does the XP988 kit fit?
2003-and-earlier Chevrolet Gen III LS engines — 4.8L, 5.3L, 6.0L and 6.2L. For 2004-and-later Gen III/IV engines, use XP981 instead.
What's the difference between XP988 and XP987?
Fitment is the same; the drive is not. XP988 uses a 12-point head, XP987 uses a hex head. The 12-point gives better socket engagement in tight pockets, which is worth having if you're working with the engine in the chassis. Torque values differ between the two kits, so use the specs printed for the kit you actually bought.
What size thread chasers do I need?
Two: M11 x 2.00 (CS324) for the primary bolt holes and M8 x 1.25 (CS317) for the small ones.
Building the whole engine?
If the block is out and apart, the bottom end is worth the same attention as the deck. See our LS main stud kit (MS334) and the LS flexplate bolt kit (XP983).
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: XP988 manual (web edition 2026.08).
PACKAGE CONTENTS
VEHICLE FITMENTS
⚠️ PROP 65 WARNING
CALIFORNIA WARNING: Cancer and Reproductive Harm -www.P65Warnings.ca.gov
