BEARINGS MAIN 85-10 GM/Isuzu/Satu V6 2.8L 3.1L 3.4L 3.5L 3.9L/173 191 207 213 237 12V 24V DOHC OHV (LZ8, LZ9)

Cylinder Head Rebuilding Process

1. Initial Inspection: As a unit comes to our shop, we give it an initial inspection to determine whether there is any reason the head should not proceed to rebuilding. This quickly catches problems such as cracks, casting damage and other conditions that would halt the process for that casting.

2. Teardown: The cylinder head is fully disassembled, which reveals other areas of potential damage to the casting. The parts and the head are separated and go through different cleaning processes.

3. Cleaning: Cast iron heads are cleaned in a thermal cleaning system — baked at 600° to reduce grease and oil to ash, then put through a steel-shot machine for a brilliant finish. Aluminum heads are baked at a lower temperature or put through a high-pressure wash, then glass-beaded.

4. Head Inspection: After cleaning, heads are pressure tested or Magnafluxed to find any cracks. All bolt holes, valve guides, valve seats and other areas are inspected for broken bolts, broken taps, cracked guides and other impairments. Straightness and cam bore wear are also checked.

5. Machining: All heads have guides installed to meet OE conditions and are resurfaced to far exceed factory specifications for surface finish. A three-angle valve job achieves valve seat runout under .001". Valves are ground for a perfect seal between valve and seat.

6. Assembly: New OE-style valve guide seals are installed. Springs are tested for proper seat pressure. Valve seat sealing is vacuum-checked for an airtight fit. Lifters are bled and rebuilt for zero lash after startup. Cams are polished and clearances are checked twice to meet OE oil clearances.

7. Final Inspection: Every head is visually inspected — surface finish, lash, bolt holes and all other areas — to ensure a quality cylinder head.

Questions about our cylinder head services? Call 1-866-766-9955.

Warranty — 12 months from purchase

Match the head before installation. We will not warranty an incorrectly installed head. Call us immediately with any questions or concerns about your purchase.

First 3 months:

1. Repair or replacement of the cylinder head.
2. Gasket set supplied for reinstallation.
3. Labor calculated from book time at $25.00 per hour, up to a maximum of 10 hours.
4. Replacement of fluids and filters.

Remaining 9 months:

1. Repair or replacement of the cylinder head.
2. Gasket set supplied for reinstallation.
3. Replacement of fluids and filters.
4. No labor is covered.

Warranty is void if:

1. The head was improperly installed.
2. The head was overheated (heat tab melted or missing).
3. The head received insufficient oiling.
4. The cooling system operated improperly.

Warranty returns must be sent to Allied Motor Parts uncleaned and fully assembled — any disassembly voids the warranty — and must be accompanied by proof of purchase. There is no warranty on threaded bolt holes after installation.

This warranty is in lieu of any other warranty, expressed or implied, including any implied warranty of merchantability or fitness for a particular purpose.

Download the full process & warranty (PDF)

Here’s why our cylinder heads stand out:

Thorough Inspection: Every head undergoes a complete teardown, cleaning, and detailed inspection for cracks and imperfections.

Advanced Cleaning: Thermal cleaning for cast iron and high-pressure washing for aluminum ensures a brilliant finish.

Precision Machining: CBN resurfacing, triple-angle valve cuts, and guide installations exceed OEM specifications.

Rigorous Testing: Vacuum tests, tension checks, and pressure tests guarantee performance and durability.

High-Quality Components: New seals, plugs, and rebuilt lifters ensure optimal functionality.

Final Assurance: Each head is inspected, stamped, and stored in a climate-controlled environment.

Wide Availability: Over 2,000 cylinder heads for all makes and models, ready for repair or exchange.