Piston Ring Set, 90.5mm, 1.5 X 2 x 4, for Aircooled VW

OVERVIEW

When it comes to building a high-performance air-cooled engine, the internal seal is everything. This Grant Piston Ring Set for 90.5mm pistons is the professional choice for enthusiasts and engine builders looking to restore compression and ensure long-term reliability. Grant has been a cornerstone in the piston ring industry for decades, and their specific configuration for the Volkswagen market is designed to withstand the extreme thermal cycles inherent in air-cooled designs. Whether you are refreshing a tired 1776cc or 1914cc street engine or assembling a brand-new performance powerplant for your Beetle, Karmann Ghia, or custom Dune Buggy, these rings provide the precise tension and metallurgy required to seat quickly and stay sealed under pressure. Don''t settle for inferior rings that lead to premature blow-by and oil consumption; trust the brand that has powered more VWs across the finish line than any other.

This specific set features the popular 1.5mm top ring, 2.0mm second ring, and 4.0mm oil scraper configuration, which is standard for most high-quality 90.5mm piston sets. The 90.5mm bore is widely considered the "sweet spot" for performance builders because it offers a significant displacement increase over stock while maintaining enough cylinder wall thickness for cooling and structural integrity. These rings are engineered with high-grade materials that provide excellent heat dissipation and wear resistance, ensuring that your Volkswagen engine maintains its peak horsepower and torque for years to come. By choosing Grant, you are investing in a product that meets or exceeds original equipment specifications, providing a level of confidence that only comes with decades of specialized manufacturing expertise. It''s the ultimate insurance policy for your engine''s bottom end.

FITMENT

These piston rings are designed for air-cooled Volkswagen Type 1, 2, and 3 engines that have been machined or equipped with 90.5mm "Big Bore" pistons and cylinders. Common fitments include:

• Volkswagen Beetle: 1954-1977 (Sedan & Convertible)
• Volkswagen Super Beetle: 1971-1979
• Volkswagen Karmann Ghia: 1956-1974
• Volkswagen Bus / Type 2: 1955-1971 (With Type 1 based engines)
• Volkswagen Type 3 (Squareback, Fastback, Notchback): 1961-1973
• Volkswagen Thing / Type 181: 1973-1974
• Custom Applications: Sand Rails, Dune Buggies, and Trikes utilizing 90.5mm bore Type 1 engine cases.

SPECS

• Brand: Grant Piston Rings
• Part Number: G1991
• OEM Reference: 311-198-16990
• Piston Diameter: 90.5mm
• Top Compression Ring Thickness: 1.5mm
• Second Compression Ring Thickness: 2.0mm
• Oil Scraper Ring Thickness: 4.0mm
• Material: High-performance cast iron/steel alloy
• Engine Type: Air-cooled VW Type 1, 2, and 3
• Set Quantity: Complete set for four (4) pistons

PRO TIPS

1. Precise Ring Gapping is Non-Negotiable

Even though these rings are manufactured to high tolerances, you must always check the end gap of every single ring before installation. Insert the ring into the cylinder about one inch down, using a piston to ensure it is perfectly square. Use a feeler gauge to measure the gap. For an air-cooled VW, a general rule of thumb is .004 inches of gap for every inch of bore diameter, but always consult your specific engine builder''s manual. If the gap is too tight, the ring ends will touch as they expand from heat, leading to catastrophic cylinder wall damage or broken ring lands. It''s much better to spend an extra hour gapping now than to pull the engine apart again in 500 miles.

2. Proper Ring Orientation and Staggering

When installing the rings onto the piston, pay close attention to the "Top" markings or dots on the rings. These must face the combustion chamber (upward) to function correctly. Furthermore, you must stagger the ring gaps to prevent "blow-by." A common practice is the 120-degree method, where the gaps are spaced evenly around the piston circumference. Ensure that no gap is aligned with the piston pin or the thrust face of the piston. This creates a labyrinth seal that keeps compression in the combustion chamber and oil in the crankcase, ensuring your VW runs clean and makes maximum power.

3. Critical Break-In Procedures

To ensure these Grant rings seat properly against the cylinder walls, you must use a high-quality, high-zinc (ZDDP) non-detergent break-in oil. Modern synthetic oils are often too "slippery" for the initial break-in phase and can cause the cylinders to glaze over, preventing the rings from ever seating. During the first 20 minutes of operation, vary the engine RPM and avoid idling for long periods. Once on the road, use moderate acceleration and engine braking (deceleration) to load the rings. This pressure forces the rings against the cylinder walls, creating the microscopic wear pattern necessary for a lifetime seal. Change the break-in oil and filter after the first 500 miles to remove any assembly debris and wear particles.