Hi
Solder the metal parts.Use Devcon [made in usa]liquid epoxy on the Ali.The devcon is drillable and can be tapped.Will take heat as I have used it to fill corosion holes in full size International Tractor engines.Have used to fix a small hole in my Mccoy60 for about 4 years.The black one seems best.Buy the primer as well.Question.If smooth flow is so good,how come all modern perpormance parts have a slightly rough[like very fine sand]finish.I tThink its called lanimer flow.If you go back to the days when Australia held the America,s Cup,the year we lost it to the USA,the american boat had very fine grooves in the hull to promote turbulance,where as Aust had a mirror finish on the hull.Those fine grooves are generally considered why your boat was faster than ours.Those boats wers state of the art.Race engine builders in Aust don,t polish ports nowdays but leave that fine sandy finish to stop the gas flow from sticking to the port walls.