Paul Yaw wrote:

Hey Ed,

You make a good point in your message, and I agree that the internet is
full of "unproven facts."  I do not have an opinion as to what gets
posted on the website, but I do have an opinion about plugs up.  Chris
Ross and I have this argument at least once a month.  I admit that I
have no way to prove this, but I feel that running plugs up is a bad
idea.  In looking at the oil drain situation, I cannot guess what exact
problems may be caused, because I cannot watch the oil flow with the
engine running.  As for the water, I REALLY dislike the idea of having
the hottest point of the water jacket at the top of the engine.  This is
a problem area even with the engine mounted conventionally.  As I said
before, I cannot prove my assertions, but as an engine builder, I am not
comfortable with the idea of supplying an engine that will be run plugs
up.

I have spent a great deal of time trying to decrease the metal
temperatures in this area, and I still feel that there is room for
improvement.  I have considered adding some clear vent/recirculation
tubes to the plug area of the water jacket to see if there is any steam
in there.  I am worried about steam pockets in a conventionally mounted
engine!  It seems that the only way to accurately assess the situation
is to run two engines for the same amount of time, at the same power
level with both configurations, and then disassemble and inspect them.
I do not see this happening anytime soon.

Smokey Yunick modified a Chevy cylinder head years ago by attaching a
piece of plexiglass so that he could see the water flowing through the
passages.  What he found was a whole bunch of steam pockets.  Obviously
it is not fair to say that "If the Chevy did it, the Mazda does too."
but it is food for thought.

Until I can prove to myself that running plugs up is OK, I would not
recommend it.  I would rather take that approach, than to wait for
someone to prove that it is a bad idea by shipping a prematurely worn
engine back to me.

Like I mentioned before, this is just an opinion, and I am extra
conservative when it comes to engine longevity.

Good luck with your project.

Paul Yaw

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