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1955-59 Chevy Firewall Filler Panel Installation Instructions

1955-1959 smooth firewall filler panel from LS Fabrication
Safety Note

First, remove any impeding wires, bolts, screws, and/or braces from the outside wall and the same from the inside of the cab. There should be no interior, wires, or impeding parts or materials that could damage or catch fire.

Install Steps

  1. Check fitment and mark. Place the filler panel onto the outside of the driver and passenger side firewall and check fitment. With a permanent marker, trace a reference line along the edge of the filler onto the existing firewall — do the same for both driver and passenger.
  2. Note factory bolt locations. Reference any factory bolt locations you want to retain — e.g. hood hinges and mounting brackets along the original firewall or brake booster — and write down the measurements for later. (Panels don’t come pre-drilled, due to cab and year diversity.)
  3. Cut the old firewall. Using a cutoff wheel or electric grinder with a cutoff disk, remove your firewall. Cut inboard roughly ½″ along the marked reference line — masking tape can help guide your spacing.
  4. Clean the lip. Leaving a ½″ lip around the existing firewall gives the new fillers a slight edge to rest on for welding. Clean the perimeter with a grinding disk or abrasive tool to remove old paint or rust — you’ll need clean metal for welding.
  5. Transfer hinge holes. Take both passenger and driver fillers and transfer the hood hinge hole location (and brake booster location if desired). Drill holes into the fillers for the hood hinges, then place the hood hinge brace on the inside driver and passenger side for reattachment — we suggest welding the braces on.
  6. Position and tack weld. Place the filler panel into the opening until it lines up nicely with the top and outside edge, then tack weld it into place.
  7. Finish welding. If you’re happy with the placement, tack weld around the perimeter at 1″ intervals to minimize warping. Once welded, grind down your welds and prep for body work.

Filler panels are usually fitted alongside a full firewall or toe board replacement. Both, plus Altman door latches and billet interior hardware, are in our 55-59 truck parts collection.

For any questions or concerns with your install, don’t hesitate to email us at info@lsfab.com

Printable instructions

The illustrated version of this guide, ready to print for the shop.

Parts used in this guide

2 Comments

  1. Shane Letcher

    Can you leave the existing firewall in place and bolt over the old

    Reply
    • admin

      Yes you can!

      Reply

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