My water temp has been running between 199 and 217, depending on the OAT.  The oil is pretty steady at around 175.  Today I finally got to fly with pressure probes inside the cowling.  I was all set to try and enlarge the inlet to the radiator to solve the problem.  It turns out that “in” is not the problem, it is “out” that is the problem!

I have 10 inches of Hg pressure in the radiator inlet and 10 inches of Hg on the outlet side as well as the same pressure everywhere I measured inside the cowl.  I need to open up the cowl some so more air can get out.  I had considered a cowl flap but that would not work in this instance because the problem is at cruise.  I need a permanent opening.  I am considering louvers and I am looking for a source.  I know some of you are using them.  Where did you get them and how are they installed so that they look ok?

I am also considering some kind of flare around the exit area to create a low pressure area to help suck air out.  Do any of you have those and do they seem to work?

While I look into this, I also need to do something about my muffler…Thank you, Bobby!

I wonder about that spiral muffler some of you are trying??

Bill B  9 hours and counting…

By the way, I was considering putting a 1 or 2 inch wide piece of cardboard across the bottom of the oil cooler to partially block it in the hopes that more air would then flow through the radiator.  Sort of like truckers do with the radiator in cold weather.  What opinions do you have about that idea?  I realize it would make more sense if the oil was really cool, but I think the oil might not get much hotter if an inch or so was blocked.  What do you think???