After nearly 2 years of trying to control the cooling on my engine (following it's rebuild), I have become wearily used to conducting flight tests that were either inconclusive, or which gave worse results, forcing me to "undo" some change.
On Saturday, I finally underwent an epiphany of sorts. I actually conducted a flight test and returned to home base with a totally positive result.
I have been experiencing rough running for some time at high rpm, in addition to CHTs being too high for comfort.
The solution to the rough running issue was the overhaul of my Slick magneto, which had accumulated 430 hours of use over 10 years since original install. See this link for the story.
Additionally, I have been experimenting with reducing the airflow through the oil cooler (which is mounted on the top of the firewall). I have never had an oil temperature problem; in fact, in the Winter, I have trouble getting the oil temperature high enough. What I believe I have shown is that the original oil cooler outlet was too large; it was allowing too much air to flow through the oil cooler. This has two impacts:

1. Oil temperatures too low (160-175 degrees)
2. Lack of pressure under the engine, reducing airflow through the cylinder cooling fins

On Sunday, running at 7000 feet MSL and 70 degrees OAT, I was able to run at full power for the first time since I originally broke in the rebuilt engine 2 years ago. The overhauled magneto completely eliminated the high-end vibration and noise that I had been experiencing. I ran for 5 minutes at full power, and the engine ran up to 2740 rpm. This gives me some room for further increases in rpm as I take drag out of the airframe (for example, fairing the gear legs will certainly gain me 4-5 mph).
CHTs were 355, 350, 370 and 350. Not quite where I need them to be (I would like to see 340 max on all 4 cylinders) but this is a 20 degree reduction across the board, all of it achieved by reducing the size of the oil cooler airflow opening, using a piece of aluminum cut to shape and inserted under the oil cooler between the bottom of the cooler and its mounting frame.
I did try blocking off the oil cooler air outlet completely, but at this time of the year here in Dallas, the ambient temperatures in the middle of the day are brutal, and the oil temperatures rose to over 200 degrees in level flight, which is too high. However, I may re-instate the blocking plate to close off the oil cooler in the Winter, when historically I have had trouble getting the oil temperature above 160 degrees.
I am currently working on improvements to the cooling for #3 cylinder. I expect to flight test those improvements this weekend. If I can get #3 to run at 350 or less down low here in Dallas at this time of the year, I will be able to confidently run anywhere in level flight without worrying any more about CHTs, which will eliminate one constant item that I have had to monitor while in the air. (As an example of the level of compromise I have been operating under - I flew all of the way to Mojave for Burt's birthday celebration in 2003 effectively running an O-235 Long-EZ, unable to run much above 2300 rpm because of high CHTs. That made for a much slower and bumpier flight; I have the war story to tell about being shaken-not-stirred while I flew across New Mexico and Arizona).
After all of the modification and hacking that I have engaged in over the last 18 months, my cowlings look like a dog's dinner, and drag reduction and cooling experts like Gary Hertzler and Terry Schubert will no doubt burst out laughing when they see the plane. However, at this point in time, being able to fly with safe CHTs and actually run at full throttle trumps aesthetic and airframe drag considerations. Since the lower cowling was a pre-built part, and is way too heavy, I will probably build a replacement this Winter. That replacement will hopefully reduce drag. Other drag will be taken out by fairing the gear legs, which may also improve airflow into the engine compartment.

Link: http://www.ntsb.gov/ntsb/brief.asp?ev_id=20040205X00164&key=1

...Not because of what they tell me about my plane, but because of what they tell me about some of my fellow pilots.
Here is another report of a pilot who became a statistic. But....read his medical condition history and tell me, would you accept a ride from somebody with this history if you knew it? Maybe there is a market for engine-driven ICUs...

I woke up at 6.00 am this morning (and that is a real shock for my body, let me tell you). After resuscitating my brain with some tea, gathered together my flying gear and drove down to RBD.
(NOTE - RBD used to be known as Redbird, until 3 years ago when it was renamed Dallas Executive - that's the name that the City of Dallas chose in order to take us up-market so as to attract more dollars-to-noise conversion machines. There seems to be more jet traffic now, and a nice shiny new FBO opened a couple of year ago, but the City has yet to spend a cent on re-surfacing either of the runways, and those runways are getting bumpier every month, which is not good for a Long_EZ).
Arrived at RBD to find the ceiling at 8-900 feet, mostly overcast. This was vaguely reminiscent of the Spring or Fall weather in my home town of Margate, UK, except that in the UK it would be around 44 degrees; here it was 72 degrees. The amusing thing was hearing the AWOS intone "Temperature 19, Dew point 17..."
Just after I arrived there was a large patch of blue sky directly overhead, and a couple of small planes made a run for it. Then the clouds descended again, and the only activity after that was a King Air which snuck in on the ILS, and a helicopter who called in to land, and after being told that the field was IFR, remembered his FARs, smacked his forehead, and requested an SVFR landing clearance, which was promptly granted.
My flying compadres scattered around the Metroplex reported similar conditions i.e. IFR or marginal SVFR at best. None of us wanted to lift off in marginal/scud-running conditions for a 1.5 hour flight, especially with weather reports showing that nearly all of the enroute airports and our destination were also marginal VFR.
We waited until around 08.40, then, by common consent via the cellphone network, we all decided to abandon the plan to fly to Hondo. Postponed until tomorrow or Sunday. Apologies to Skip, who patiently arranged for a Friday fly-past by canards at Hondo. Next time, Skip, next time...

Link: http://www.aopa.org/whatsnew/newsitems/2005/050512fox.html

...step forward Fox News (forgive me while I feign surprise). Seems like Fox has to engage in the most peurile rabble-rousing imaginable. I will be interested to see what the Fox response is to the AOPA president, but I'm not holding my breath waiting for anything approaching a mea culpa. More than any network in the USA, Fox seems to spend the most time obeying the old tabloid maxim that one should never let the facts get in the way of a good story...

Those of you who have had the (mis)fortune to engage me in canard conversation in the last 2 years will know that I had my engine rebuilt due to assembly deficiencies. After breaking-in the engine, it became clear that due to the new engine having more horsepower than the old engine, cooling was inadequate.
For the last 18 months I have been making all sorts of modifications to the cowlings on my plane to try and bring down the CHTs to what I consider to be a safe operating level. During that time I have hardly ever run the plane at full power in level flight - I could not do so due to CHT issues.
I can report that I made a breakthrough last week. After failing to get the CHTs below 375 at 2500 rpm for a while, I flew home last weekend after getting my prop dynamically balanced. At 2540 rpm, 3500 feet and OAT of 65 degrees, I saw CHTs as follows:

#1: 355
#2: 350
#3: 370
#4: 350

I achieved this significant improvement by simply blanking off 50% of the opening in the top cowling where cooling air flows through the oil cooler (my oil cooler is on the top of the firewall, with exit air exhausting out onto the dorsum).
Oil temperatures in level flight were around 190 degrees.

So...working on the principle that I might as well go the whole way, I then blanked off the entire opening. This time, at similar outside conditions, I saw the following:

#1: 350
#2: 350
#3: 360
#4: 350

The oil temperature was around 195 degrees.

I now believe that the CHT issue was caused by the fact that the opening in the top cowling was allowing too much pressurised air to bypass the cylinders. The air was taking the line of least resistance.
Prior to trying this modification, I had made all sorts of other changes including adding armpit scoops to the lower cowlings, adding exit ramps over the cylinders in the top cowling, changing the airbox profile and angle inside the cowling etc. etc. None of those modifications made any significant difference, still leaving me 30-40 degrees higher than where I think I need to be for safety.
I will now blank off the additional armpit scoops to see if I can get a further reduction in CHTs. (With multiple inlets in a cowling it is possible for air to enter one inlet and exit from another inlet if there is any significant pressure differential between the 2 inlets. This effectively loses cooling air out of the lower cowling, reducing airflow through the cylinders).
I intend to fly to the EAA Hondo fly-in this weekend with the plane in that modified configuration, to assess performance on a long flight.
I may yet need to reverse all of the other cowling modifications that I have made over the last 18 months.
This, folks, is what I think they meant when my elders talked about "learning from your mistakes"...