Changes

Changes. What did I change from the original engine to the second engine that had the fat fin heads? Not much. I would have to write a book to itemize all the changes and their effects I have done since I first test flew the plane but I changed very little from the 40 hour mark up to when the engine came off  the firewall for the power loss, at about 80 hours, I think.
  Here are those changes...and why I did it.
Camshaft timing advanced 4 degrees. Why? I was disappointed by the climb rate of my 701 on the original engine and I had done several tests trying to improve that, but the problem had ALWAYS been heat. I could not sustain full power long enough to get good data but I knew the engine could do better. My fuel burn showed that. So when I decided to put the engine back on the airframe I gave up all hopes of just getting in the plane and zipping off to a fly-in, I changed to developmental, see what happens if I do this mode. I began looking for ways to improve low end torque with exactly the same parts as before to put to rest some of the myths I had heard over the years. One of those myths is changing the camshaft timing in relation to the crankshaft would alter the powerband, or rpm that the engine makes the most torque. The problem was I couldn't get two people to agree on which way to go. So I experimented. My engine machinist said for lower torque to advance it and others said to retard it. So I looked on the net.
http://www.compcams.com/technical/FAQ/LSAproperties.asp
I looked at a bunch of stuff but I figured these dudes had a better than average chance of knowing what they were talking about.
  My camshaft gears are adjustable, 4 degrees advance, straight up and 4 degrees retarded. When I set the engine up the first time I assembled it straight up. The second time I decided to try and make more bottom end torque and advanced it based on what I saw on the Comp Cams site, and on advice of my buddy Vic Dawson. I figured if it didn't work out I'd just pull the oil pump and go the other way, which I'm sure is easier said than done. The results later.

 Another change I made was to the cylinder baffling, I removed, or I should say I chose not to install the cool tin baffling on the bottom. This was going to save some weight but meant new block off baffles would be required. This time instead of putting the baffles on top of the cylinders I chose to put them on the bottom, just like the real engines have it. The holes you can see in the aluminum plates are to hold them in place. I used a piece of heavy steel wire to go up through the fins to a bracket or fin on top to haold it in place, again, like on many certified installations.
 Compression ratio is the second thing, I raised it abou .4 to around 8.6 to 1. Every change  made was expected to increase the power output of the engine and therefore the amount of heat to be rejected. I was very confident that the fin extensions would help if they stayed on, I just didn't know how much or how little the effect would be.  All that was left was to hang it back on the plane and see what I had.
 One statistic most are interested in is weight. I completely assembled the engine and weighed it on an engine hoist. I had heard that the redrive engine would weigh about 185 lbs, and I wanted to know. My 701 came in at 742 lbs empty and I knew I didn't add that much junk to it. I figured the biggest weight penalty was in the engine but I was shocked at what I found. With everything on it that would be there when it was on the plane except the prop the package came in at 223 lbs. This includes all the baffling, exhaust, intake system, dual ignition which includes a 4216 mag setup, oil cooler with brackets etc. Like I said, everything as it would hang on the plane. Oh well......a little more than than 185.

  Then, the weather hit. On the day I planned to mount it up I got out of bed and the outdoor temperature was 6, yea 6, as in 6 degrees fahrenheit. This meant that my hanger, which is unheated was also 6 degrees inside since the snow was blowing in the cracks of the siding. I put on my work clothes and insulated coveralls and went to work. Global warming my butt, you can't prove it by me. I had the engine hanging pretty quick and began hooking up all the sytems and controls until I froze out. Warmer weather was coming though........

This shot is before the fat fin mod, the reason I included it here is to show the hanger, not much more than a barn but at least I'm dry!