CMI Precision Machining

CMI Precision Machining Parts for Air-Cooled VW

CMI Precision Machining is a machine shop based in Corona, California that makes billet and high-strength steel parts for air-cooled Volkswagens. CB Performance, CMI's main dealer, lists its CMI parts as made in the USA. Washburn's Metal carries the CMI parts that solve real problems on street, off-road and drag-race VWs, and we have checked every listing against the dealer's published specifications.

Washburn's Metal is an authorized CMI Precision Machining dealer — genuine CMI parts, made in the USA, with full factory support.

What CMI makes

• Valvetrain: CMI billet roller rocker arm kits in 1.4:1 (blue end caps) and 1.5:1 (black end caps) ratios for the Type 1 engine. They have 7050-T651 hard-anodized rocker bodies, DLC-coated 9310 steel shafts, H13 tool-steel adjusters with titanium 12-point lock nuts, and oil that is force-fed from the pushrods to the shafts and roller tips.
• Driveline: 300M steel racing swing axles for 1961-1966 Beetle and Ghia sedans. They are hand-polished and lapped to 4 max RMS, black oxide finished, with J-threads that have a 0.3mm root radius.
• Axle hardware: flanged 4340 nickel-plated axle nuts heat-treated to 54-56 HRC, and 17-4 stainless swing axle thrust washers heat-treated to H900.
• Engine and chassis hardware: a 17-4 H-900 stainless crank pulley bolt and stepped centering washer, and M18 x 1.5 stainless rear transmission cross brace bolts, both hardened to 40-44 RC with J-threads.
• Controls: the "4 Banger" clutch cable adjusting knob. It is 7075-T651 billet, black anodized, with 19mm of thread engagement, and it clears the motor mount bolt.
• Pulleys: CMI billet crank and alternator/generator pulleys and trigger wheels.

Why the materials matter

CMI's parts are specified by alloy and heat treatment rather than just "steel" or "aluminum": 7075-T651 and 7050-T651 aluminum, 17-4 stainless in the H900 condition, 4340 alloy steel and 300M steel. Several CMI fasteners use precision-cut "J" threads with a controlled root radius, which CMI specifies to prevent cracking.

Buying CMI parts from Washburn's Metal

Every CMI listing includes the CB Performance cross-reference number, fitment, specifications and a short FAQ. If a supplier does not publish a dimension such as a thread pitch or washer thickness, we say so on the listing rather than guess. We will help you confirm fit before you order, so contact us with your year, model and build details.

Frequently asked questions

Where is CMI Precision Machining located?
Corona, California.

Are CMI parts made in the USA?
Yes. CB Performance lists CMI parts as made in the USA.

Do CMI rocker kits fit Type 4 engines?
No. They are for Type 1 engines.