Cylinder Shim Set, Fits, 90.5 & 92mm, .010 In Thick, 4 Pc

Precision Deck Height Control for High-Performance Air-Cooled Engines

When you are building a high-performance Volkswagen engine, precision isn''t just a luxuryit''s a requirement. The EMPI Cylinder Shim Set for 90.5mm and 92mm bores is an essential tool for the serious engine builder looking to "square" their engine block and achieve the perfect deck height. Deck heightthe distance from the top of the piston at Top Dead Center (TDC) to the top edge of the cylinderdirectly dictates your compression ratio and your quench area. Without the use of precision shims like these .010-inch units, you are at the mercy of factory machining tolerances and aftermarket part variances. These shims allow you to fine-tune the position of your cylinders, ensuring that all four pistons have identical clearance, which leads to a more balanced, smoother-running, and significantly more reliable engine.

Constructed from high-grade steel to withstand the immense heat and pressure cycles inherent in an air-cooled environment, these shims are designed specifically for larger bore diameters. Whether you are building a 1776cc, 1835cc, or 1914cc powerhouse, these .010-inch shims provide the "fine-tuning" capability that thicker shims cannot offer. Often, a case may be slightly "out of square" from previous line bores or deck resurfacing; by using a combination of shim thicknesses, you can compensate for these imperfections without the need for costly custom machining of the piston tops. This set of four ensures that your entire engine bank is consistent, protecting your investment from the dangers of pre-detonation or piston-to-head contact during high-RPM operation.

Detailed Fitment Guide

These cylinder shims are designed for Volkswagen Type 1 based engines utilizing 90.5mm or 92mm cylinder sets. This includes, but is not limited to, the following applications:

• Volkswagen Beetle: 1954 through 1977 (Sedan and Convertible)
• Volkswagen Karmann Ghia: 1956 through 1974
• Volkswagen Bus / Type 2: 1954 through 1971 (with Type 1 based engines)
• Volkswagen Thing / Type 181: 1973 through 1974
• Volkswagen Squareback, Fastback, Notchback / Type 3: 1962 through 1973
• Custom Applications: Dune Buggies, Sand Rails, Trikes, and Kit Cars utilizing VW 1600cc based upright engines bored for 90.5mm or 92mm cylinders.

Technical Specifications and Materials

Every engine builder knows that the devil is in the details. Here are the technical specifications for the EMPI 4559-10 shim set:

• Bore Compatibility: Fits both 90.5mm and 92mm Cylinder Barrels
• Shim Thickness: .010 Inches (0.25mm)
• Material: High-Quality Cold-Rolled Steel for maximum compression resistance
• Quantity: Set of 4 Shims (One per cylinder)
• Outside Diameter: Precision matched for "Machine-In" style engine cases
• Manufacturer: EMPI
• Part Number: 4559-10

Pro Tips from the Appletree Master Technician

1. Always Perform a "Dry Fit" Measurement

Never assume your deck height is correct just because you are using "stock" length components. Before final assembly, install your pistons and cylinders without rings or sealant. Use a deck height gauge or a depth micrometer to measure the distance from the piston crown to the cylinder top at absolute TDC. Measure all four cylinders. It is common to find variances of .005 to .015 inches between cylinders. Use these .010 shims to bring the "low" cylinders up to match the "high" ones, ensuring a perfectly balanced compression ratio across all four combustion chambers.

2. Calculating Your Compression Ratio

Adding a .010-inch shim does more than just move the cylinder; it increases the volume of the combustion chamber. For a standard 90.5mm bore, every .010 inches of deck height adds approximately 1.6cc to your total combustion volume. If you are trying to hit a specific compression ratio (CR) for pump gas, such as 8.5:1, moving from a .040 deck to a .050 deck using these shims can be the difference between an engine that pings under load and one that runs flawlessly for years. Always re-calculate your CR after selecting your shim thickness.

3. Proper Sealing Techniques

While the shim itself acts as a spacer, you still need to ensure a leak-free seal at the base of the cylinder where it meets the engine case. We recommend a very thin, almost transparent smear of a high-quality non-hardening sealant like Curil T or Permatex Aviation Form-A-Gasket on both sides of the shim. Do not use RTV silicone, as it can "squish" and create a bead that interferes with the shim''s seating or, worse, break off and clog oil passages. A properly seated shim is vital for heat dissipation from the cylinder back into the engine case.