Copper Cylinder Head Gaskets, Fits 90.5 & 92mm, 050 Thick

OVERVIEW

When you are building a high-performance air-cooled engine, precision is the difference between a motor that screams and one that scatters. These EMPI copper cylinder head gaskets are the professional builder''s secret weapon for perfecting deck height and fine-tuning compression ratios. Designed specifically for 90.5mm and 92mm bore cylinders, these .050-inch thick shims provide a reliable, malleable seal between the cylinder top and the cylinder head. In the world of Volkswagen performance, maintaining a consistent quench area is vital for preventing detonation and ensuring efficient combustion. By utilizing high-quality copper, these gaskets offer superior thermal conductivity compared to standard steel or composite alternatives, helping to pull heat away from the combustion chamber and into the cylinder head cooling fins more effectively.

At Appletree Auto, we know that standard "out of the box" tolerances often aren''t enough for a custom stroker motor or a high-revving street machine. Whether you are building a 1776cc, 1835cc, or a 1914cc powerhouse, these copper gaskets allow you to compensate for machining variations in the case or heads. Copper is the preferred material for serious engine builders because it is soft enough to conform to minor surface irregularities while remaining durable enough to withstand extreme cylinder pressures. These shims don''t just adjust your compression; they act as a high-performance seal that prevents the dreaded "head leak" that can plague air-cooled engines under heavy load. If you are looking to maximize the longevity and power output of your VW Beetle, Bus, or Sand Rail, these .050-thick copper shims are an essential addition to your engine assembly kit.

FITMENT

These copper cylinder head gaskets are designed for Volkswagen Type 1 based engines utilizing performance big-bore cylinders. Fits the following applications and engine builds:

• Volkswagen Beetle: 1950 through 1979 (With 90.5mm or 92mm cylinders)
• Volkswagen Karmann Ghia: 1956 through 1974 (With 90.5mm or 92mm cylinders)
• Volkswagen Bus / Type 2: 1950 through 1971 (With 90.5mm or 92mm cylinders)
• Volkswagen Type 3 (Squareback, Fastback, Notchback): 1962 through 1973
• Volkswagen Thing: 1973 through 1974
• Dune Buggies, Sand Rails, and Trikes: Utilizing VW Type 1 upright engine configurations
• Engine Sizes: Specifically for 1776cc (90.5mm), 1835cc (92mm Thick Wall), and 1914cc (92mm) displacements

SPECS

• Material: High-Grade Annealed Copper
• Bore Diameter: Fits 90.5mm and 92mm Cylinders
• Thickness: .050 Inches (1.27mm)
• Quantity: Sold as a set of 4 gaskets
• Manufacturer: EMPI
• Part Number: 4579-21
• Function: Deck height adjustment and cylinder-to-head sealing
• Compatibility: Works with most aftermarket dual-port and single-port cylinder heads

PRO TIPS FROM THE SHOP

Tip 1: Verify Your Deck Height Before Final Assembly

Never assume your deck height is correct just by looking at it. Before installing these .050-inch copper gaskets, you must measure your "piston-to-deck" clearance without any shims installed. Ideally, you want a finished deck height (the distance from the top of the piston at TDC to the top of the cylinder) between .040 and .060 inches for a street-driven VW. If your raw measurement is .005 inches, adding this .050 shim will put you perfectly at .055 inches. This ensures you have enough room for rod stretch and thermal expansion at high RPMs, preventing the piston from making catastrophic contact with the cylinder head. Proper deck height is the key to a cool-running, knock-free engine.

Tip 2: Surface Preparation is Critical for a Leak-Free Seal

While copper is excellent at conforming to surfaces, it isn''t a "fix-all" for warped heads or pitted cylinder tops. Before installation, ensure that the seating surface of the cylinder head is perfectly clean and flat. We highly recommend "lapping" the cylinders to the heads. You can do this by applying a small amount of fine valve grinding compound to the top of the cylinder and rotating the head back and forth against it until a uniform matte-gray ring appears on both surfaces. Once cleaned, install the copper shim dry or with a very light coating of a high-temp sealant like Permatex Copper Spray-A-Gasket to ensure a microscopic seal that won''t blow out under high compression.

Tip 3: Annealing Copper Shims for Maximum Softness

If you are a seasoned builder and you find that your copper shims have been sitting in a toolbox for a long time, they can occasionally work-harden. To ensure they are as soft and pliable as possible for the best seal, some builders choose to "anneal" them. You can do this by carefully heating the copper gaskets with a torch until they reach a dull cherry red color and then immediately quenching them in clean water. This process softens the molecular structure of the copper, allowing it to "crush" slightly and fill in every tiny imperfection between the head and the cylinder. Just be sure they are perfectly flat and free of scale before you drop them into your high-performance long block.