66 Porsche Inner Rocker Panel Replacement Part: A Complete Guide

Finding the correct inner rocker panel for a 1966 Porsche is crucial for restoring structural integrity and appearance. This guide covers everything you need to know about choosing and installing a replacement part for your 911 or 912.

What Is the Inner Rocker Panel and Why Replace It?

The inner rocker panel runs along the lower side of the chassis, just inside the outer rocker sill. It provides structural support, helps seal the cabin from moisture and road debris, and serves as a mounting point for the outer rocker panel and floor pan. On a 1966 Porsche, these panels are prone to rust due to trapped moisture, salt, and age. If you notice bubbling paint, soft spots, or visible holes along the rocker area, it's time to replace the inner panel. Ignoring it can lead to compromised structural integrity and more extensive corrosion in the floor pan and heat exchangers.

Key Considerations When Buying a 66 Porsche Inner Rocker Panel

OEM vs Aftermarket Parts

Original Porsche parts are NLA (no longer available) for many early 911 and 912 models. Most restorers turn to high-quality aftermarket reproductions. Reputable aftermarket panels are made from steel that matches the original gauge and shape, often with correct hole placements for the lower control arm mounts and heat exchanger pass-throughs. Some suppliers offer "repair sections" that cover only the rust-prone lower portion, while others provide full inner rocker panels that replace the entire length from the front splash shield to the rear bulkhead.

Material Quality and Gauge

Original inner rockers were stamped from 0.8mm to 1.0mm sheet steel. Aftermarket panels vary: cheaper ones may use thinner steel that deforms under load or rusts quickly. Look for parts made from cold-rolled steel with a minimum thickness of 1.0mm. Some premium manufacturers use zinc-coated steel for added corrosion resistance. Avoid fiberglass or aluminum panels for this structural part—they do not weld well and can fatigue over time.

Fitment and Dimensions

Early 911 and 912 chassis evolved slightly through 1966. Verify that the panel is designed for a 1966 model year, as later 1967+ panels have differences in the front section to accommodate the changed suspension and sway bar mounting. A good aftermarket panel will include pre-drilled holes for the jacking point mounts and the floor pan flange. If the part requires major trimming or bending, it may be a poor reproduction. Check supplier photos or forums for real-world fitment reports.

Included Hardware and Extras

Some inner rocker panels come with the rubber seal that fits between the inner and outer rocker panels, but many do not. You may also need a bag of spot weld rivets or Bondo-style seam sealer for welding. Verify what is included before ordering. Common additional parts are the jacking point bracket and the lower hinge reinforcement plate, though these are often sold separately.

How to Install a 66 Porsche Inner Rocker Panel

Installation is a structural repair that requires welding and bodywork skills. If you are not experienced with welding, consult a professional restoration shop. Here is a general outline of the process:

Preparation

1. Remove the outer rocker panel, trim, and any rust-damaged areas of the floor pan. Clean the area down to bare metal, removing all rust and old seam sealer.
2. Support the car on jack stands to avoid flexing the frame when the old rocker is cut out.
3. Measure and mark the location of the new panel. Use the door gap and the existing floor pan flange as references.

Cutting and Removal

4. Use a cutoff wheel or plasma cutter to remove the old inner rocker, cutting along the factory weld seam. Be careful not to cut into the floor pan or the A- and B-pillar flanges.
5. Grind down the remaining weld tabs and clean the mating surfaces.

Test Fit the New Panel

6. Hold the new inner rocker in place. It should fit snugly against the floor pan flange and the front/rear pillars. Use clamps or self-tapping screws to temporarily hold it. Check the door gaps; you may need to adjust the panel position slightly before welding.
7. If the panel has a locating hole for the jacking point, ensure it aligns with the corresponding hole in the floor.

Welding and Sealing

8. Weld the new panel in place using a MIG welder with 0.023 wire and CO2/argon mix. Use short stitch welds to prevent warping. Weld along the floor pan flange, the front and rear pillars, and the wheel well flange.
9. After welding, grind the welds smooth and apply seam sealer to all joints to prevent future moisture ingress.
10. Paint the rocker area with a high-quality epoxy primer and topcoat before installing the outer rocker panel and sill trim.

Common Mistakes to Avoid

• Using too thin steel: If the new panel is thinner than 1.0mm, it will not be strong enough to support the car on a jack or handle the loads from the suspension.
• Ignoring the heat exchanger pass-through: The inner rocker has holes for the heat exchanger tubes. If the reproduction lacks these holes, you must drill them precisely to avoid exhaust leaks.
• Overtightening clamps before welding: This can distort the panel. Use light pressure and check fitment frequently.
• Skipping corrosion protection: Even with zinc-coated panels, paint the inside of the rocker cavity with anti-rust paint or cavity wax after installation.

Top Suppliers for 66 Porsche Inner Rocker Panels

Several reputable manufacturers produce inner rocker panels for early 911/912:

• Stoddard (Vintage Parts LLC) – Known for high-quality steel panels made in Germany. Their inner rockers are often the standard for concours restorations.
• Restoration Design – Offers a complete inner rocker assembly including the backbone brace. Their panels come in heavy-gauge steel with correct contours.
• Pelican Parts – Stocks OEM-spec panels from various aftermarket brands; they have good customer service and can help with fitment questions.
• Sierra-IP – Provides budget-friendly options that are acceptable for driver-quality cars. Check reviews for fitment consistency.
• Classic 911 Parts – A specialist for early 911 body panels; they often have original Porsche dies and produce panels that drop in with minimal adjustment.

Cost and Value

A single inner rocker panel for a 1966 Porsche typically costs between $150 and $400, depending on brand and completeness (full panel vs repair section). Shipping can be expensive because panels are large. A full set (both sides) may run $500–$800. In addition to the panel, budget for welding supplies, seam sealer, paint, and possibly a professional welder's labor ($300–$600 per side). While it may be tempting to buy the cheapest panel, a poorly fitting part can cause more frustration and cost more in bodywork corrections than a high-quality one.

Final Recommendation

For a concours restoration, go with Stoddard or Restoration Design. Their panels are worth the extra money for perfect fitment and original appearance. For a driver-quality car where you plan to drive and enjoy the car, a Pelican Parts or Classic 911 Panel will serve well. Always order from a supplier that offers a return policy and technical support. If you are unsure about installation, have a professional do the welding. The inner rocker panel is a structural part; safety and long-term durability should be your top priorities.