Cylinder Shim Set, Fits 94mm, .090 Thick, 4 Pc

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

When you are building a high-performance air-cooled Volkswagen engine, precision is the difference between a motor that screams and one that self-destructs. This EMPI Cylinder Shim Set is specifically engineered for 94mm bore cylinders, providing a robust solution for builders who need to dial in their deck height with absolute accuracy. In the world of VW engine assembly, deck heightthe distance from the top of the piston at Top Dead Center (TDC) to the top edge of the cylinderis the most critical variable for determining your compression ratio and ensuring proper piston-to-head clearance. These .090-inch thick shims are particularly vital for stroker engine builds where longer crankshaft throws push the pistons further out of the barrels, necessitating a spacer to maintain the ideal "squish" area and prevent catastrophic internal contact.

Constructed from high-quality materials to withstand the intense thermal expansion and contraction cycles of an air-cooled environment, these shims offer a reliable alternative to the costly and time-consuming process of machining piston tops or cylinder bases. By utilizing these .090 shims, you can effectively "shim out" the cylinders to achieve a specific combustion chamber volume, allowing you to run higher boost levels in turbocharged applications or manage heat in high-compression naturally aspirated street engines. Whether you are building a 1915cc, 2276cc, or a massive 2332cc powerhouse, this set of four shims ensures that all four cylinders are perfectly matched, providing the structural integrity and sealing surface required for a long-lasting, leak-free engine build that Appletree Auto customers demand.

Comprehensive Fitment and Application Guide

These 94mm cylinder shims are designed for Type 1 based engines utilizing "Big Bore" 94mm cylinder barrels. This includes a wide range of custom and performance configurations across the following models:

• Volkswagen Beetle: All years utilizing 94mm performance engine builds (1915cc and larger).
• Volkswagen Karmann Ghia: Performance builds requiring specific deck height adjustments.
• Volkswagen Bus / Type 2: Ideal for heavy-duty 94mm builds in Split Window and Bay Window models.
• Volkswagen Type 3 (Squareback, Fastback, Notchback): Fits Type 1 based performance conversions.
• Volkswagen Thing (Type 181): Perfect for off-road builds where compression management is key.
• Sand Rails and Dune Buggies: The industry standard for high-displacement 94mm air-cooled racing engines.

Technical Specifications and Dimensions

Designed for professional engine builders, these shims meet exact tolerances to ensure uniformity across your engine block. Don''t settle for inferior spacers when your tolerances are measured in thousandths of an inch.

• Cylinder Bore Diameter: 94mm (Standard Big Bore).
• Shim Thickness: .090 inches (2.286mm).
• Material: Precision-stamped high-tensile steel for maximum durability and heat resistance.
• Set Quantity: 4 Pieces (Complete set for one engine).
• Compatibility: Fits between the cylinder base and the engine case.
• Manufacturer: EMPI.
• Part Number: 4571-90.

Pro Tips from the Appletree Auto Engine Shop

Pro Tip #1: Always Perform a Mock Assembly. Never assume your deck height will be perfect based on math alone. Assemble your crank, rods, and pistons into the case without rings first. Use a depth micrometer or a deck height bridge tool to measure exactly how far the piston sits in the hole at TDC. Once you have your baseline measurement, you can accurately determine if these .090 shims will bring you to your target deck height (typically .040 to .060 inches for most street-performance builds). Measuring twice ensures you don''t have to tear the long block apart later.

Pro Tip #2: Account for Compression Ratio Changes. Adding a .090-inch shim significantly increases the volume of the deck area, which will lower your static compression ratio. For every .010 you add in shim thickness, you are adding roughly 1.5cc to 1.8cc to your combustion volume on a 94mm bore. Before final installation, use a CC kit to measure your cylinder head volume and run the numbers through a compression calculator. This ensures your engine isn''t "lazy" due to unexpectedly low compression or "detonation-prone" due to being too high.

Pro Tip #3: Proper Sealing is Mandatory. While some builders install these shims dry, many master builders recommend a very thin, almost transparent smear of a high-quality sealant like Permatex Aviation Form-A-Gasket or Curil-T on both sides of the shim. This prevents annoying "weeping" oil leaks at the base of the cylinders. Ensure the engine case surface and the cylinder base are clinicaly clean and free of any old gasket material or nicks before sliding the shims over the studs. Even a tiny piece of debris under a .090 shim can cause the cylinder to sit crooked, leading to premature ring wear or head gasket failure.