How to Install Aluminum Cylinder Heads on a Chevy 350

Aluminum cylinder heads offer superior heat dissipation and weight savings compared to cast iron alternatives, making them a popular upgrade for performance enthusiasts rebuilding small block engines like the Chevy 350. Proper installation is critical to prevent leaks, warping, or catastrophic failure. This guide outlines every essential step, from initial preparation to final torquing, ensuring a secure fit and reliable operation.

Understanding Aluminum Cylinder Heads and Their Benefits

Aluminum cylinder heads excel in high-performance applications due to their lightweight construction and excellent thermal conductivity. These heads typically feature larger valves and optimized ports for improved airflow, which can significantly increase horsepower and efficiency. However, their softer material requires careful handling during installation to avoid galling or thread damage.

When upgrading from stock heads, expect gains in power output, but always match the heads to your engine’s compression ratio and camshaft specifications. Common applications include small block Chevy engines, where aluminum heads reduce overall engine weight by up to 50 pounds per pair.

Gathering Essential Tools and Materials

Before starting, assemble the right tools to streamline the process and minimize errors. Key items include:

• Torque wrench (accurate to 1 ft-lb increments up to 100 ft-lbs)
• Thread chaser set for cleaning bolt holes
• Paint scraper or plastic razor blades for surface cleaning
• Brake cleaner and lint-free rags
• Permatex thread sealant with Teflon or assembly lube
• Hardened washers (required to prevent galling)
• Head gasket matched to your engine block
• Microfiber cloths for final wipe-down

Additionally, source quality head bolts or studs rated for aluminum applications. For engines with power adders, opt for ARP high-strength fasteners.

Preparing the Engine Block Surface

Cleanliness is paramount; any debris or old gasket residue can compromise the seal. Begin by removing all remnants of the previous head gasket using a paint scraper. Avoid metal tools that could gouge the block deck.

Spray brake cleaner liberally and wipe with a clean rag until the surface is mirror-like. Inspect for warpage using a straight edge and feeler gauge—maximum allowable distortion is 0.004 inches for most blocks. If exceeded, machine the deck flat.

Next, chase all head bolt threads with the appropriate tap. Older engines often have carbon buildup or damaged threads, which must be cleared to ensure proper torque application. This step can take considerable time but prevents uneven clamping forces.

Selecting and Positioning the Head Gasket

Choose a multi-layer steel (MLS) gasket for aluminum heads, as it provides the best conformity to minor surface imperfections. Verify orientation: the side with continuous metal rings around cylinder bores faces upward.

Align the gasket using the locating dowels or pins on the block. Press firmly to seat it fully. Double-check that all cylinder cutouts match the block bores perfectly—no overhangs or shifts.

Common Gasket Mistakes to Avoid

Placing the Aluminum Cylinder Head

Lower the head onto the block, guiding it over the dowel pins at each end. Ensure it seats fully without rocking. Aluminum heads are prone to scratching, so wear gloves and use a lifting strap if needed for heavy units.

Inspect the head’s combustion chambers and ports for debris. A quick compressed air blast clears any particles.

Installing and Torquing Head Bolts

Aluminum heads demand specific torque specs: 65-70 ft-lbs for most small block Chevy applications, or 70-75 ft-lbs with factory bolts and sealant. Always use thread sealant like Permatex with Teflon on bolts to prevent hydraulic lock from blind holes.

Place hardened washers under each bolt head to distribute load and prevent aluminum galling. Hand-thread all bolts finger-tight first, ensuring no cross-threading.

Torquing Sequence and Procedure

Follow the manufacturer’s torque sequence—typically a spiral pattern starting from center bolts outward. For GM small blocks:

1. Torque all bolts to 40 ft-lbs in sequence.
2. Increase to 50 ft-lbs.
3. Final torque to 65-70 ft-lbs (or specified value).

Use a calibrated torque wrench and turn smoothly without jerking. For high-compression or boosted engines, re-torque after initial run-in once fully cooled.

Post-Installation Checks and Assembly

After torquing, rotate the crankshaft by hand two full turns to check for binding. Install pushrods, rocker arms, and set valve lash per specs (common for solid lifters: 0.020″ intake/0.022″ exhaust cold).

Prime the oil passages by pouring oil into the head and spinning the oil pump. Install intake manifold, exhaust headers, and timing cover next.

Safety Precautions and Best Practices

• Work in a well-ventilated area; engine oils and cleaners are hazardous.
• Disconnect battery and relieve fuel pressure before starting.
• Wear safety glasses during scraping and cleaning.
• Never reuse head bolts unless specified as TTY (torque-to-yield) replacements.
• For performance builds, consider head studs over bolts for repeated teardowns.

Troubleshooting Common Issues

If the head doesn’t seat properly, recheck dowel alignment. Bolt binding indicates unclean threads—chase again. Post-install leaks often trace to improper torque sequence or insufficient sealant.

Monitor for overheating on first runs, as aluminum heads run hotter initially until broken in.

Performance Optimization Tips

Pair aluminum heads with matching pistons to achieve desired compression (9.5:1 typical for street use). Port matching enhances flow. After 500 miles, re-torque to account for heat cycling.

Frequently Asked Questions (FAQs)

Do I need special bolts for aluminum heads?

Yes, use ARP or OEM-grade bolts with washers. Standard bolts may strip aluminum threads.

What’s the ideal torque for Chevy 350 aluminum heads?

65-75 ft-lbs in stages, following GM sequence.

Can I install heads without removing the pistons?

Yes, on most small blocks, but TDC alignment helps with valve-to-piston clearance.

How do I know if my block deck is flat enough?

Check with straight edge; machine if over 0.004″ warp.

Should I use RTV sealant on the gasket?

No—MLS gaskets seal dry. RTV is for corners only if specified.

Advanced Considerations for High-Performance Builds

In forced-induction setups, upgrade to copper gaskets and O-ringing the block for extreme pressures. CNC-ported aluminum heads from reputable manufacturers like Airflow Research optimize flow for 500+ HP. Always dyno-tune after installation.

Maintenance involves periodic torque checks every 10,000 miles. Aluminum’s expansion rate differs from iron blocks, so use compliant gaskets.