Originally Posted by
HondaRules!
I agree with this, 100 %. The heat from welding the flange to the IM, will cause the surface to warp and distort. Perhaps it won't be enough to cause a problem with the gasket you use, perhaps it will. It's best to have it finish machined when you're finished! Especially as it will likely only cost a few $$....
And you have a 0.55" flange to start with, so you can lose a few thou during surfacing and still have a massively overbuilt flange.