Cylinder Shim Set, Fits, 90.5 & 92mm, .090 In Thick, 4 Pc

OVERVIEW

Precision is the cornerstone of any high-performance air-cooled Volkswagen build, and achieving the perfect deck height is arguably the most critical step in that process. This EMPI Cylinder Shim Set is specifically engineered for 90.5mm and 92mm bore engines, providing a robust solution for builders who need to fine-tune their engine''s geometry without the costly and permanent alternative of machining pistons or cylinder heads. By utilizing these .090-inch thick shims at the base of your cylinders, you gain total control over your combustion chamber volume and quench area. Proper deck height is essential not just for hitting your target compression ratio, but also for ensuring optimal flame travel and preventing catastrophic piston-to-head contact during high-RPM operation. Whether you are building a spirited street cruiser or a dedicated drag racer, these shims provide the repeatable accuracy required to balance all four cylinders perfectly.

Constructed from high-grade materials designed to withstand the intense heat and constant vibration of a flat-four engine, these shims are a staple in the toolbox of every master engine builder. When you increase the stroke of your crankshaft or use long-throw connecting rods, you often find that the piston crown extends too far out of the cylinder or doesn''t reach far enough to provide efficient combustion. This .090-inch set offers a significant adjustment range, allowing you to "shim out" the cylinder to create the necessary clearance. Because these are manufactured to exacting tolerances, they provide a perfectly flat mating surface between the cylinder base and the engine case, which is vital for preventing oil leaks and maintaining structural integrity under load. Don''t leave your engine''s longevity to chance by guestimating your deck height; use these professional-grade shims to dial in your build with the precision it deserves.

FITMENT

This cylinder shim set is designed for VW Type 1, 2, and 3 air-cooled engines equipped with 90.5mm or 92mm "thick wall" or "thin wall" cylinders. This includes, but is not limited to, the following models:

• Volkswagen Beetle: 1954-1977 (Standard and Super Beetle)
• Volkswagen Karmann Ghia: 1956-1974
• Volkswagen Bus / Type 2: 1950-1971 (With Type 1 based upright engines)
• Volkswagen Type 3 (Squareback, Fastback, Notchback): 1961-1973
• Volkswagen Thing / Type 181: 1973-1974
• Custom Dune Buggies, Sand Rails, and Trikes: Utilizing VW 1600cc-based crankcases.

SPECS

Technical specifications for the EMPI 4559-90 shim set are as follows:

• Compatible Bore Sizes: 90.5mm and 92mm
• Shim Thickness: .090 Inches (2.28mm)
• Material: High-Tensile Steel
• Quantity: 4 Pieces (Complete set for one engine)
• Manufacturer: EMPI
• Application: Cylinder Base Shim for Deck Height Adjustment
• Part Number: 4559-90

PRO TIPS

1. Always Measure Twice Before Final Assembly

Never assume that your deck height is uniform across all four cylinders just because you are using a new case and new cylinders. Before installing your rings, perform a "dry fit" of your pistons and cylinders on the rods. Use a deck height bridge tool and a dial indicator to measure the distance from the top of the piston at Top Dead Center (TDC) to the top of the cylinder. If your measurement is too tight (typically anything under .040"-.050" for a street engine), these .090" shims can be used to bring your clearance into the safe zone while simultaneously lowering your compression ratio to a pump-gas-friendly level.

2. Use the Right Sealant Sparingly

When installing these shims at the base of the cylinder, it is tempting to use a thick layer of RTV silicone. Don''t do it! Excessive silicone can squeeze out and clog oil passages or cause the cylinder to sit unevenly. Instead, use a very light smear of a high-quality, non-hardening sealant like Curil T or Permatex Aviation Form-A-Gasket on both sides of the shim. This ensures a liquid-tight seal against the engine case while maintaining the precise thickness of the shim for accurate deck height calculations.

3. Account for Compression Ratio Changes

Adding a .090" shim is a significant move that will noticeably lower your static compression ratio. Every master builder knows that deck height and combustion chamber volume work together. If you are trying to tame a high-compression engine to prevent detonation (pinging), these shims are your best friend. However, make sure to use a compression calculator to see how that .090" increase in deck height affects your final numbers. If it drops the compression too low, you may lose power; if it''s still too high, you might need to combine these with chamber work or a different shim thickness to find that "sweet spot" of performance and reliability.