Mark Leal wanted to dress up the 348 engine in his '59 Impala but couldn't find any contemporary-style aftermarket valve covers for 348/409 applications. So, decided he'd "whittle away" on some aluminum to see what he could build on his own.
He's been to a lot of Ron Covell metalworking workshops and felt confident enough to tackle the job. Not having a shop full of metal-forming tools, or Covell's talent at freehanding sheetmetal, Mark came up with a simple forming jig, to make the job a little simpler. The only tools required were a bandsaw, a router, and a TIG welder, along with simple handtools. The only special skill is being able to weld aluminum with an acetylene torch. Mark photographed the process, step by step, to share his idea with other 348/409 Chevy owners. Follow along.
Aluminum Welding
While the valve covers seen here were TIG-welded, it's possible to MIG-weld aluminum with the right equipment. It may be possible to convert your MIG welder with different shielding gas (100 percent argon is required for aluminum) and accessories, though purchasing a spool gun from Miller is by far the easiest way we've seen of late. However, this will obviously depend on you owning or considering purchasing a Miller welder! We'll show these two options further on, but let's take a look at the differences between aluminum and steel, and why the former is considerably harder to weld, whether by MIG or TIG.
Unlike steel, aluminum will not tolerate paint, oxidation, grease, or other contaminants when being welded. Correct surface preparation is vital to remove lubricants or dirt, and can be tackled using solvents. Removing any oxides is of equal importance after degreasing. When exposed to air, aluminum forms a hard oxide layer on its surface. The melting point of this layer is roughly three times that of aluminum-3,700 degrees Fahrenheit compared to 1,200 degrees-and this is why the oxide layer must be removed prior to welding, using a stainless steel wire brush. It's important to use a brush that will only ever be used to clean aluminum, to keep from contaminating the weld site.
You should also be aware of the specific alloy you wish to weld, as the quality of the finished weld will be enhanced by using a filler wire recommended for that particular alloy. ER4043 and ER5356 are the most readily available from local welding supply houses, and they come in various size spools, just as regular filler wire does for welding steel. ER4043 contains silicone, while ER5356 has magnesium content. This allows the latter to have a faster melt-off rate. It is stiffer and easier to feed and is preferable in rigid, high-strength applications. ER4043 is popular, as it is adaptable to many aluminum base metals and is ideal for non-critical work. As with steel filler wire, different wire diameters are available, and owing to aluminum filler wire's soft nature, a thicker wire will feed more easily. The thickness of the material to be welded is a consideration, too, as it's difficult to weld aluminum thinner than 14-gauge without specialized equipment.
Miller Electric Mfg.Miller has introduced the Spoolmate 100 Series spool gun to be used in conjunction with its MIG welders in order to weld aluminum. Full details on how to use the spool gun can be found on Miller's Web site, but suffice it to say, there are some differences compared to a normal MIG welder when used to weld steel. It requires a 10- to 15-degree push travel angle to place the shielding gas in front of the bead, with the contact tip recessed 1/8-inch inside the nozzle. While you may be used to welding steel with 1/8- to 1/4-inch of wire sticking out from the contact tip, aluminum requires 3/8- to 1/21/2-inch. Large beads should be avoided on aluminum, and torch travel speed should be greater than when welding steel, since the material becomes heated, though heat needs to build up at first before travel speed is picked up.
The first step in making my...
The first step in making my valve covers was to build an accurate forming jig. I began by tracing the flange of a stock cover onto a piece of 1/2-inch steel plate. If you don't have a valve cover to work from, you could use a gasket, or create a pattern by taking a rubbing off the cylinder head using a piece of heavy paper. Pipe and pipe sections were cut and tack-welded to the 1/2-inch plate for use as forms for the various curves and corners of the jig. Note that the flange mounting holes have been drilled into the plate. A piece of 1/8-inch steel flat plate was then cut and welded to form the straight portions of the jig.
Another piece of 1/8-inch...
Another piece of 1/8-inch steel plate was formed, cut, and welded to make up the two large curved portions of the jig. At this point, all welds were ground to provide a smooth surface for forming the aluminum. The flat and curved clamping blocks were made from steel.
A piece of 0.090-inch-thick...
A piece of 0.090-inch-thick 3003-H14 aluminum was cut to form the curved side and two short ends of the cover, from one bolt recess area all the way around to the bolt recess area on the other end (arrows).
The aluminum was annealed...
The aluminum was annealed by applying a coat of carbon soot from an acetylene torch (acetylene only, no oxygen), then heated with a neutral flame (acetylene and oxygen) until the black soot was burned off. This process takes the temper out of the aluminum, softening it to be more easily shaped. Don't quench it, but let it air-dry and it will retain the desired shape without springing back.
With the aluminum centered...
With the aluminum centered and clamped onto the center of the jig using the large flat clamping block (A), the curved clamping plates (B) were used to smoothly draw the aluminum into the curved portions of the jig. A hardwood block (not shown) and a dead-blow hammer were used to smoothly bend the aluminum around the large recess curves to the corner of the cover. One of the smaller flat clamping bars (C) was used to hold the aluminum in place as it was hammered around the end corners. The end portions were then clamped to the jig. The bolt recess areas were formed using 1-inch-od aluminum tubing with 1/8-inch wall thickness.
On the opposite panel of the...
On the opposite panel of the cover, the center bolt recess area was TIG-welded to 0.090-inch-thick 3003-H14 aluminum on each side, using 1100 aluminum rod. These flat pieces do not need to be annealed.
The flat aluminum stock was...
The flat aluminum stock was cut to fit the corner bolt recess pieces and welded in place (A). The long piece of stock I started with was then bent around the corner and welded to the bolt recess pieces (B). This completed the forming of the valve-cover body. Gentle heat may be required on the entire aluminum body for easy removal from the jig.
A test-fit on an engine ensured...
A test-fit on an engine ensured proper fit at this point. Notice how well the annealed aluminum retained its shape after removal from the jig.
The jig was used to scribe...
The jig was used to scribe the inside cut of the flange onto a piece of 1/4-inch-thick 6061-T6 aluminum. The outside cut line was scribed 1/2-inch outside of the inside line, and the flange was cut. Note the inside access cut at the lower left (arrow). Once the interior and exterior cuts were complete, the access cut was welded up and sanded smooth. Since the flange is under some stress when bolted to the head, 4043 aluminum rod was used on this weld.
The rough-cut flange was bolted...
The rough-cut flange was bolted to a master flange used as a template and cut to match on an overhead arm router (a regular router used in a table would work, as well). I used an ordinary wood-cutting carbide-tipped 1-inch flush-trim pattern bit with a ball-bearing follower. The outside was cut in the same manner. Hand bar soap was used as a lubricant to produce a smooth cut, so precise that the master and cut flange appeared to be a single unit.
The flange was placed on the...
The flange was placed on the motor to test for proper fit and then clamped and tacked to the valve-cover body on the inside using 3/32 4043 aluminum rod.
The valve-cover body was used...
The valve-cover body was used to scribe the cut line for the top of the valve cover onto a sheet of 1/8-inch 3003-H14 aluminum. The tops were carefully cut to fit snuggly inside the valve covers' bodies.
Approximately one half of...
Approximately one half of the top thickness was left exposed above the top of the body to provide a good lip for the fillet weld. The top was tacked in place to ensure flatness, then welded with 3/32 1100 aluminum rod.
After completing the weld,...
After completing the weld, the top was sanded to provide a smooth surface for the base of the router to ride on. An ordinary router with a woodworking carbide-tipped 5/32-radius round-over bit was used to cut a uniform radius where the top and the sides meet. Again, hand bar soap was used as a lubricant.
Finally, the valve covers...
Finally, the valve covers were buffed and polished.