Cylinder Shim Set, Fits 94mm, .040 In Thick, 4 Pc

Product Overview: Precision Deck Height Control for High-Performance VW Engines

When you are building a high-performance air-cooled Volkswagen engine, precision is the difference between a motor that screams down the track and one that suffers from catastrophic failure. This EMPI Cylinder Shim Set is specifically engineered for 94mm bore cylinders, providing a crucial .040-inch lift at the base of the barrel. In the world of VW engine building, achieving the perfect deck height is paramount for controlling your compression ratio and ensuring that your pistons don''t make unwanted contact with the cylinder heads. These shims allow you to fine-tune that critical gap between the top of the piston at Top Dead Center (TDC) and the top of the cylinder ridge without the expensive and permanent need for machining your pistons or the engine case deck. Whether you are building a 1914cc cruiser or a massive 2332cc stroker, these shims provide the repeatable accuracy required for a professional-grade assembly.

Constructed from high-quality materials designed to withstand the intense heat and constant vibration of a flat-four powerhouse, these shims provide a stable foundation for your cylinders. By using these .040-inch shims, you can effectively lower your compression ratio to a pump-gas-friendly level or compensate for a stroker crankshaft that is pushing the pistons too far out of the hole. This set of four ensures that all cylinders are spaced equally, maintaining balanced compression across both banks of the engine. Don''t settle for "close enough" when it comes to your quench area and combustion chamber volume. These shims are an essential tool in any master engine builder''s arsenal, allowing for the exact mechanical tolerances that define a reliable, high-output air-cooled Volkswagen engine. At Appletree Automotive, we know that the smallest measurements make the biggest impact, and these EMPI shims are the industry standard for getting the job done right.

Vehicle Fitment and Compatibility

These 94mm cylinder shims are designed for aftermarket "Big Bore" applications. While 94mm cylinders were not factory equipment, they are the most popular choice for performance builds. These shims fit the following models when equipped with a Type 1, 2, or 3 engine case machined for 94mm barrels:

• Volkswagen Type 1: Beetle and Super Beetle (1954-1977)
• Volkswagen Type 2: Bus, Transporter, Kombi (1954-1971)
• Volkswagen Type 3: Fastback, Squareback, Notchback (1961-1973)
• Volkswagen Karmann Ghia: (1955-1974)
• Volkswagen Thing: (1973-1974)
• Custom Applications: Dune Buggies, Sand Rails, and Trikes using VW-based air-cooled engines.

Technical Specifications and Dimensions

Precision is non-negotiable in engine assembly. Here are the detailed technical specifications for the EMPI 4571-40 shim set:

• Bore Size Compatibility: 94mm (Standard for 1914cc, 2007cc, 2110cc, 2180cc, 2276cc, and 2332cc builds).
• Shim Thickness: .040 Inches (Approx. 1.016mm).
• Material: High-grade, heat-resistant steel/alloy construction for maximum durability and minimal compression set.
• Quantity: 4 Pieces (Complete set for one engine).
• Placement: Installs between the cylinder base and the engine case mating surface.
• Manufacturer: EMPI
• Part Number: 4571-40

Pro Tips from the Appletree Specialist Team

1. Always Measure Your Deck Height Twice

Before you finalize your shim selection, you must measure your "zero shim" deck height. Use a deck height gauge or a depth micrometer to find out how far the piston sits in the hole (or how far it protrudes) at Top Dead Center. For a street-driven air-cooled VW, the "Sweet Spot" for deck height is typically between .040" and .060". If your piston is flush with the top of the cylinder (.000 deck), adding this .040" shim set will put you exactly where you need to be for a safe and efficient quench area. Never guess on this measurement; a deck height that is too tight can lead to the piston hitting the head at high RPM due to rod stretch and thermal expansion.

2. Account for Compression Ratio Changes

Remember that adding a .040" shim doesn''t just change the physical clearance; it increases the volume of the combustion chamber, which lowers your compression ratio. When you are "CC-ing" your heads, make sure to include the added volume created by the shim in your calculations. This is a great way to "detune" a race engine for the street or to make a high-compression stroker engine more compatible with 91 or 93 octane fuel. If you find your compression is still too high after adding .040" shims, Appletree carries multiple thicknesses that can be stacked or swapped to reach your target PSI.

3. Proper Sealing and Cleanliness

When installing these shims, the mating surfaces on both the engine case and the bottom of the cylinder barrels must be surgical-grade clean. Any piece of grit or old gasket material will cause the cylinder to sit crooked, leading to base leaks or even cylinder head sealing issues later on. While many builders install these shims dry, a very light "smear" of a high-quality non-hardening sealant (like Permatex Aviation Form-A-Gasket) can help ensure a leak-free seal. Avoid using heavy RTV silicone, as it can squeeze out and migrate into the oil galleries, which is a leading cause of bearing failure in freshly built engines.