Custom Hood Modifications- Converting a Multi-Piece Hood to One Piece

One thing that I’ve planned to customize on Project Pile House from day one was the hood. The hood on the truck is a “butterfly” (as I call it) style hood and was a design that Dodge rolled over from the 40’s. I have taken a 50’s custom type approach to this truck and that style hood wasn’t going to flow. I decided to disassemble the hood and convert it to a one-piece hood.

I started by cutting along the “hinges” of the hood and separating it into three pieces. I then used a flap disc on the angle grinder and sanded the remainder of the hinge flange flat so the seams where I was welding the hood together were smooth. I’ve read a number of different ways that guys have converted their hoods to one piece including welding the seam then grinding the back flange down, putting a backer plate under the seam, etc. I decided I wanted to butt weld the joints and hammer the welds flat as I went to keep everything straight.

The hood really never fit correctly from the beginning and the front center nose section was bent from years of abuse. The metal was even ripped a little where it had been flexing all these years! I test fit the hood pieces and adjusted the gaps a little bit to get it sitting close to where I wanted. Once I was happy with how it was going to fit I turned the hood upside down and clamped it to the welding table to keep the two weld seams even. I then tack welded the side closest to the windshield first and slowly worked my way across the top of the hood. Once I had the top and back tack welded I carefully flipped the hood over and continued to tack weld along the front of the hood.  As I worked my way forward I slowly pulled the bent front center section in to match the contour of the left and right sides of the hood.

With some help I carefully test fit the hood again to check the fitment and shape. I was pretty happy with how the front of the center section fit the sides so I took it back to the workbench to continue welding. Ideally I would have liked to weld the hood with the TIG 200, but the hood was a bit rough to get the perfect seams I wanted to lay nice TIG welds. I decided to use the MIG 175 and hammer each batch of spot welds to keep the hood flat. TIG welds are softer than MIG welds so you can hammer them afterwards. MIG welds tend to get very hard and brittle after they cool, so it’s best to hammer them immediately when they are at their softest.

Ideally you should have a helper to hold the dolly or work the hammer for a large panel like this, but it can be done alone (I did this alone).  The goal is to jump around the panel laying 1-3 spot welds at a time and immediately hammering the weld “on-dolly”. Hammering the still-hot spot welds on-dolly stretches the metal and counteracts the shrinking caused by heating the seam when welding. The key is to strike the hot MIG welds a handful of times at a mid-range force (you’re not driving a nail into a 2×4!).  Next you want to jump across the panel to an area that isn’t hot to the touch (without a glove on) and repeat the process. Make sure you take a break after making a pass over the entire panel and check your progress (or take a photo, sip a drink, etc.) and let the panel cool. I like to use a straight edge over my weld seams to make sure there isn’t any major shrinking that I need to address immediately.

With a large panel like this hood that had two seams, the “weld, hammer, let cool” process took three 2-3 hour sessions to get both seams fully welded.  I made sure I test fit the hood after each welding session to make sure nothing was getting out of shape. You never can be too careful when welding up such a large panel!

Once I verified the seams weren’t out of shape I used a 3 inch Surface Conditioning Disc on the small Pneumatic Angle Grinder to knock the proud welds down. Be sure to grind across the weld seam and don’t sit in one spot for too long as it can heat and warp the panel! Ideally the hammering and welding process should have flattened the welds and you shouldn’t have too many proud welds to knock down. I then worked out any minor small low or high spots on the seam with the Fairmount Hammer and Dolly and refit the hood to the truck.

Now that the hood is truly one-piece I need to make new hood support straps for the underside of the hood to help it keep its shape. Then I can work on fabricating hood hinges and a new latch as the hood will be opening from front like most other cars from the 50’s and on. Stay tuned for part 2 where I tackle these next mods!            -Matt/EW

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