I recently purchased a MSA coated square port header for the 2.9L E88 that goes in my '72 240z.  I have the engine on the stand and figured I would mock everything up before dropping it back in the car.  The fitment between the header flange and my Interpart triple carb manifold is very tight as the #1 and #6 exhaust port flange is touching/pressed against the intake manifold.  The lower thermostat housing is also touching the flange.  Before I grind some of the flange material away on the header I wanted to ask, have any of you run in to this before?  If so, did you grind the header flange or the intake manifold?  I don't want to grind the any material off the lower thermostat housing as I believe it needs all the material it can get.  I welcome thoughts and opinions.  Thank you! 

I don't have any answer but if you grind the flange that will remove the coating. How will you prevent rust or more coating lifting in these ground areas?

My first thought would be to grind the flange because it appears to have more disposable material

@PatconPreventing rust was my concern as well.  I believe my only option would be some silver high temp. paint sprayed over the spots that exposed the bare metal.

Are they aluminum or some type of steel? I ask because I had to grind my ceramic 6to1 where the 6 met into 1 and rubbed the bell housing. I've checked it many times usually when changing out the oil and there's still a nice clean cut. No rust after 6 or 7 years?

  On 5/6/2019 at 12:05 AM, siteunseen said:

Are they aluminum or some type of steel? I ask because I had to grind my ceramic 6to1 where the 6 met into 1 and rubbed the bell housing. I've checked it many times usually when changing out the oil and there's still a nice clean cut. No rust after 6 or 7 years?

I am confidant they're steel. I assume yours hasn't rusted because it doesn't get wet. ?

I must agree Charles, they rarely get out of the gayrage.

Lots of meat on that header flange . I might consider a little sanding on the thermostat housing . I believe I had to trim the gasket too

Thank you everyone for your feedback.  I think I will start by grinding the header flange ever so slightly, just enough to keep it from touching the other components.  I don't think rust should be a huge concern but I will try to keep the area I grind down as small as possible so I protect it without compromising too much of the coating.  I plan to give it a go one night this week.

On my 240Z I had interference with the thermostat housing too. I ground a little off the thermostat housing flange.