There are 'metal-filled epoxy putty' compounds that can be used for this sort of repair. Much easier to use than the less viscous 'liquid steel' types which come in twin tube packs.
The 'ITW Devcon' product range is about the widest of these; they offer fill metals that include aluminium, bronze, steel, stainless steel and titanium.
The snag is, that even the smallest available pack of one of these putties is going to cost well over $20! And the product's service temperature limit might be a bit low, for use on an air-cooled engine.
Surface prep and cleaning/degreasing of the metal surface is critical, too, as has been said.
