I would like some opinions on a project that has been presented to me. I have been asked to repair a cast iron engine block that has broken mounting points. I haven't yet gotten the pictures but from the description two mounting "ears" have broken off and one has some metal missing and needs to be built up, drilled and tapped.
I have learned to stay away from cast iron engine block repairs as my success is 50-50 using the traditional ni-rod approach with peening. However I have started using brazing rod for repairs on the perimeter of the block where expansion and contraction is free as opposed to expansion and contraction somewhere in the main body of the block where expansion or contraction can lead to a crack as the stress is "locked" in by surrounding metal.
I have done one engine mount using brass and so far it has worked fine. However, I am unsure if this is safe as brass is softer than cast iron and I wonder if I'm exceeding the mechanical properties of the braze metal.
When I worked in the steel mills as a maintenance welder years ago we routinely repaired huge, I mean huge, heavy machine bases and parts made from cast iron using brazing rod with total success. The procedure involved pre-heating the part with propane torches for hours to get it dull red and then beginning the brazing process and keeping the heat on while the repair was being performed. Then it was covered with asbestos blankets and left to cool slowly, sometimes for a day or more.
However, unlike an engine mount, these bases were static and load bearing, not subject to pull, push forces. They were subject to impact type forces leading to the break in the parts. Generally speaking I use brazing quite a lot for some types of repairs (such as on bike frames )and have never had a part I repaired returned for a rework.
So, am I safe using brass to repair an engine mount? Is a ni-rod approach a better solution? Attached are pictures of the repair I spoke about. Any and all opinions will be welcome and appreciated.