Welding Tips and Tricks

One of my upcoming projects involves an aftermarket cast aluminum intake manifold for a small Block Chevy. It's a Miniram intake if you care to know. Most intakes have raised ridges to aid in heat dissipation but this one has milled in channels instead. It is not possible to mill the surface flat unfortunately so I need to fill it in with TIG rod, flatten it out and polish it to a mirror finish ish. Problem is that in the past I've used 4043 tig rods and once fully polished it leaves a slightly contrasting color. It a shade of white brighter. Can anybody suggest a rod that will work out best for blending in and survive in a high vibration environment with lots of heat cycles and temperatures up to 225*?

4047 for cast is a great choice, 4943 works well too.

You might look at ER5554 filler. It is a Magnesium alloy filler made for higher temperature applications. If the 4043 doesn't color match well, this would give you a different alloy that is temperature stable. I have no idea about the color match.