Re: Utilizing Silicone-Bronze filler
 

Now it has been a few years since I have used Silicone-Bronze filler, but iirc, it is good for cast to mild or ss, but not in your app. The two reasons why are heat and vibration. Now even at room temp, it has a fair bit less strength, but heat it up and it is even worse. It also does not like to be vibrated so on an engine is exactly where it was not designed to be. It does flow quite nice and is good for repairing cracks, and on thin sheet, but I wouldn't use it in this case.

I personally would just use a high nickel rod, and pre to 500F, keep it warm well welding and post heat let it cool slowly in sand or heating blankets. As for the actual rod Ni33 and Ni99 I have used both, but can be both pricey and hard to come by. Most often I use SS E309 as it is easy to find and relatively cheap, it also has a high Ni and Cr components.

In reality I would probably just go down to your local welding supply place, and ask what they have in stock, and how much. SS E309, is good stuff to have around anyway as it is a good all purpose SS rod, as well it is what you use to join mild and SS.