Copper Cylinder Head Gaskets, Fits 90.5 & 92mm .040 Thick

OVERVIEW

When you''re building a high-performance air-cooled engine, precision isn''t just a suggestionit''s a requirement for longevity and power. These EMPI copper cylinder head gaskets are the ultimate tool for the serious engine builder looking to dial in their deck height and compression ratio with surgical accuracy. Designed specifically for the popular 90.5mm and 92mm big-bore kits, these .040-inch thick shims provide that critical buffer needed to prevent valve-to-piston interference while allowing you to achieve the exact static compression ratio your cam profile demands. Whether you''re assembling a weekend cruiser or a strip-ready drag bug, having the ability to fine-tune your combustion chamber volume without constant trips to the machine shop for flycutting is a game-changer for any garage-based specialist.

Beyond just spacing, the material choice here is paramount. Copper is widely regarded in the VW community as the gold standard for sealing high-compression heads because of its unique thermal properties and malleability. As the head nuts are torqued to specification, the copper gaskets provide a superior seal that stands up to the intense heat and pressure cycles inherent in a flat-four engine. It is important to remember, however, that while copper offers an incredible seal, these gaskets are not a "fix-in-a-can" for warped heads or pitted cylinders. If your engine has been suffering from a "head leak" sound, you must ensure your surfaces are perfectly flat before installation. When used on freshly flycut heads, these EMPI shims ensure that your engine stays sealed, cool, and powerful by providing a uniform contact patch between the cylinder top and the head step.

FITMENT

These copper gaskets are designed for high-performance engines utilizing "Machine-In" style cylinders and are compatible with the following applications:

• Volkswagen Type 1: Beetle, Bug, and Super Beetle (1950-1979) equipped with 90.5mm or 92mm big bore kits.
• Volkswagen Type 2: Bus, Transporter, and Kombi (1950-1971) with performance 1776cc, 1835cc, or 1914cc engine builds.
• Volkswagen Type 3: Fastback, Squareback, and Notchback (1962-1973) using upgraded 90.5mm or 92mm cylinders.
• Volkswagen Karmann Ghia: (1956-1974) All models with 90.5mm or 92mm bore configurations.
• Custom Applications: Dune Buggies, Sand Rails, Trikes, and kit cars utilizing a VW-based air-cooled flat-four engine.

SPECS

Detailed technical specifications for EMPI Part Number 4579-20:

• Material: High-Grade Annealed Copper for maximum sealing and heat transfer.
• Thickness: .040 Inches (Approximately 1.016mm).
• Inside Diameter: Sized for 92mm cylinders (Also the standard fitment for 90.5mm cylinders).
• Quantity: Complete set of 4 pieces (Enough for one complete engine).
• Manufacturer: EMPI.
• Application Type: Cylinder Head Shim / Gasket.
• Compatibility: Fits all standard air-cooled VW "Machine-In" style big bore heads.

PRO TIPS

Tip 1: Verify Your Deck Height First

Before installing these gaskets, you must measure your deck heightthe distance from the top of the piston at Top Dead Center (TDC) to the top of the cylinder. A standard performance build usually looks for a deck height of .040" to .060". If your pistons are currently flush with the top of the cylinder (zero deck), adding these .040" gaskets will give you the perfect safety margin. Always use a dial indicator and a deck height bridge to get an exact measurement on all four cylinders to ensure your compression is balanced across the entire engine.

Tip 2: Surface Preparation is Critical

Copper gaskets are excellent sealers, but they require a pristine environment. Ensure that the top of your cylinders and the "step" inside your cylinder heads are perfectly clean and free of carbon deposits, old sealant, or nicks. If you see "black tracking" on the cylinder tops where combustion gases have been escaping, you must have the heads flycut by a machinist. Using a copper gasket on a surface that isn''t flat will only lead to a premature failure. For an extra layer of protection, some builders prefer a light spray of high-temp copper gasket adhesive, though many install them dry for a clean metal-to-metal seal.

Tip 3: The Secret to Reusing Copper Shims

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