never have and rigged a whole bunch of motors that way.everyone in our group has filter first.

well I'm going w/ the build of this motor was junk.

My company inspects heat exchangers and coolers, you would be shocked at what is left inside to be flushed by the oil/product. Not saying you wont get lucky, but why risk it?

Picture this, you take two flat pieces of metal and drill 50-100 holes thru both pieces at the same time, then you weld/solder both pieces to the end of a tube, then you push 50-100 pieces of tube thru the holes and then you weld or silver solder the tubes in place. Can you see the possibility of shavings and excess solder/weld/slag ending up on the inside?

Your brand new motor flushes the cooler into your engine.

well I do clean them before I install/rig them.but I could see a big problem if care is not taken.

flushing may work, however vibration and heat will dislodge more material. I also feel that contaminated coolers may lead to rebuilt motor failures when they are in line after the filter. Typically a failed engine ( bearings) will release enough metal to cause the filter to bypass which then fills the cooler with unfiltered oil. You can flush it but...

that's why I also run my filters after the cooler always you never know whats in there, I swore my 420's were that way from Merc but cannot remember now...

You would have to know the flow path of the oil through the filter housing to determine when it measures temp and when it filters in relation to cooler correct? I'm sure someone here knows for sure

In through the little holes out through the big hole

I mean there is an inlet/ outlet from the engine on the housing and an inlet/ outlet from the cooler on the housing with different flow paths depending on where the thermostat directs the oil. So when is temp take? When is it filtered?

I cant remember the ins and outs of the bell housing setup.