How to Fill and Shave Chevy C10 Gas Filler Hole

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When building a custom vehicle one of the most important things is cleaning up the original design of the vehicle and doing modifications that make it look better, operate safer, and perform better. Because of that it’s no surprise that most pickup trucks with gas filler necks in the cab get the tank relocated and the hole filled. This modification is going to clean up the exterior of the truck and also relocates the gas tank to a safer location. Recently we took a trip to a local Eastwood customer’s garage to help him tackle this job on his 1969 Chevy C10 Pickup project.

Kenny is a novice and we decided to lend him a hand with his project showing him the simple DIY method to shave the gas filler hole. The tools we brought were basically the bare minimum you’d need to complete this project. There are other ways to do this that may require additional tools and skills, but this way is going to be a simple, solid, repair that will last.

The original gas tank and filler neck was removed and discard first leaving us with a hole in the side of the cab. We then pried the original filler neck rubber gasket out of the hole so we could sand the paint off.  This truck has old bodywork and paint done by the previous owner and the work was far from quality. Because of this we decided to do some exploratory sanding to make sure there wasn’t any old repairs or damage surrounding the gas filler hole that we would need to address at the same time. Luckily we didn’t find much in this area and we were able to sand the area down to bare metal first.

Most pickup bodies like this have a lip that runs around the inside of the filler neck hole in the body. This lip is stamped into the body and adds some strength. In order for us to be able to hammer and dolly our patch we will need to cut or grind this lip down. If you can get to the area easily you can use aviation snips and carefully trim the entire lip off. Otherwise you can take a sander and knock the lip down until it’s flush with the backside of the panel. Make sure you’re careful with the sander and don’t gouge the base metal you’re welding on later. Now that the hole and surrounding metal are all prepped we can make our patch panel. In this case we could easily get to the backside of the panel. We then held a piece of metal on the outside and traced the gas filler hole from behind onto the metal. This allowed us to cut the patch down with the the aviation snips until it fit into the cab.

Most vehicles have compound curves in the body and require you to put some shape into the replacement panel. This patch was no different so we used the panel beater bag and a blocking hammer to put some shape into the flat metal patch. Kenny then used a hammer and dolly to smooth out the panel after we put some shape into it. This got us a panel with a slight contour to it that fit the truck nicely.

With the shape correct on the patch we were able to use a metal scribe to draw an exact line of where we need to cut the panel down so it fit the gas filler hole. We again used the aviation snips to trim the panel down until it fit inside of the original opening and was flush with the outside of the panel. We used Eastwood Stitch Weld Magnets to hold the patch flush in the cab for tack welding.

After some practice welds Kenny had the Eastwood MIG 135 dialed in for the 18 gauge steel we were using. We adjusted the welder on the “hot side” so the weld was relatively flat on the top and had close to 100% penetration. This minimized grinding and assures the panel has full weld penetration. Since Kenny is a beginner we chose to back the weld seam up with a copper backer. The backer stops the weld from blowing through and the welding wire won’t stick to it. The backers also act as a heat sink to keep the panel temps down. We took our time stitch welding the patch by alternating our welds around the patch and hammering the weld seam to keep it flush. We were careful to make sure we kept the panel from getting too hot in between stitch welds. If the metal is too hot to touch with the back of your hand it’s best to let it cool a little before continuing to weld.

After the patch was fully welded into the cab we used a die grinder to knock any proud welds down and a DA sander with 80 grit paper to blend the weld seams. Be sure to avoid gouging the metal trying to get the weld to blend out. You may need to hammer and dolly around the welds to raise the metal and reduce the warping in the panel.

In the end this job left us with a finish that requires minimal filler and is strong so it will last the life of the truck. We spent about half a day on the patch even with teaching Kenny the ropes of the Eastwood MIG 135.

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