Cylinder Shim Set, Fits 94mm, .020 Thick, 4 Pc

OVERVIEW

Precision is the cornerstone of any high-performance air-cooled Volkswagen engine build, and achieving the perfect deck height is arguably the most critical step in that process. When you are assembling a large-displacement engine using 94mm cylinders, such as a 1915cc or a stroker 2332cc, the relationship between the piston crown and the top of the cylinder barrel dictates your compression ratio and your engine''s overall efficiency. These EMPI .020-inch cylinder shims provide the necessary clearance to fine-tune your deck height without the need for costly and irreversible piston machining. By placing these shims between the cylinder base and the engine case, you can accurately dial in your quench area, ensuring that your flame front travels efficiently across the combustion chamber while preventing catastrophic piston-to-head contact during high-RPM operation.

Constructed from high-quality materials designed to withstand the intense heat and constant vibration of a Flat-Four boxer engine, this 4-piece set is an essential tool for the serious engine builder. Whether you are correcting for a case that has been surfaced too many times or you are trying to lower your compression ratio to accommodate a turbocharger or lower-octane pump gas, these shims offer a reliable and repeatable solution. Don''t settle for "close enough" when it comes to your tolerances; using a .020-inch shim allows for incremental adjustments that can mean the difference between an engine that runs hot and pings versus one that delivers smooth, reliable power for years to come. At Appletree Automotive, we know that the smallest details often yield the biggest results, and these 94mm barrel shims are the professional way to ensure your long-block assembly is up to competition standards.

FITMENT

This cylinder shim set is designed for Volkswagen Type 1 based engines that have been machined to accept 94mm cylinder barrels. This includes, but is not limited to, the following applications:

• Volkswagen Beetle: All years equipped with 94mm bore performance engines (e.g., 1915cc, 2276cc, 2332cc).
• Volkswagen Karmann Ghia: All years utilizing Type 1 94mm upgraded long blocks.
• Volkswagen Bus / Type 2: 1950-1971 models using Type 1 upright engine configurations with 94mm bores.
• Volkswagen Type 3 (Fastback, Squareback, Notchback): Models converted to 94mm performance specifications.
• VW Thing (Type 181): All years with 94mm bore performance builds.
• Custom Sand Rails and Dune Buggies: Any air-cooled VW drivetrain utilizing 94mm cylinders.

SPECS

• Bore Size Compatibility: 94mm
• Shim Thickness: .020 inches (0.508mm)
• Material: High-grade durable steel for heat resistance and compression stability.
• Quantity: Set of 4 pieces (Full engine set).
• Manufacturer: EMPI
• Part Number: 4571-20
• Application: Cylinder base to engine case interface.

PRO TIPS FROM THE SHOP

1. Always Measure Twice Before Final Assembly

Before you commit to a shim thickness, you must perform a "dry fit" of your cylinders and pistons. Torque your cylinders down using a deck height tool or old spacers and head nuts to simulate the actual clamped load. Measure the distance from the top of the piston at Top Dead Center (TDC) to the top edge of the cylinder. If your piston is "out of the hole" or the deck height is too tight (less than .040"-.050" for most street builds), these .020" shims are the perfect corrective measure. Remember that adding a shim increases the deck height and effectively lowers the static compression ratio.

2. Proper Sealing Technique is Vital

A common mistake is over-applying sealant to the cylinder shims. To prevent oil leaks at the base of the jugs, we recommend a very thin, almost translucent film of a high-quality sealant like Curil T or Permatex Aviation Form-A-Gasket on both sides of the shim. Avoid using RTV silicone, as excess squeeze-out can break off inside the case and clog oil galleys or the oil pickup screen. The goal is to create a molecular seal between the case, the shim, and the cylinder barrel without creating a thick "gasket" that could compress and change your deck height over time.

3. Account for Heat Expansion

When calculating your desired deck height with these .020" shims, remember that air-cooled engines expand significantly as they reach operating temperature. A deck height that is too tight (under .035") might provide a great quench effect, but it leaves very little room for error if your rod bearings wear or if the engine gets exceptionally hot. For most high-performance street engines, aiming for a final deck height of .045" to .060" provides a safe margin of error. These shims allow you to hit that "sweet spot" precisely, ensuring that your valves and pistons never meet, even at the top of third gear on a hot summer afternoon.