Experimenting

I had talked to many people about my flight testing with this power package on the 701 by this time and many, many, folks were asking me not to give up. I think if it had not been for all the individuals from around the world thanking me for trying and letting me know I was giving them hope for affordable flying I wouldn't be where I am now.......

 I looked up at the durafix and it hit me lick a brick! I knew the fin extensions had to help but how would a common man without a $3500.00 Tig welder get them on? Durafix! If I could make it work. Just for the record I have a Miller Dynasty 200 tig machine but I wanted to try to develop something that EVERYBODY could do.

 I came up with a fin pattern the hard way, I laid the head down on a piece of cardboard and traced the inside radius that would be brazed to the head fin. Then I used the header pipe to check the clearance and made the biggest extension I could, 1 3/8". I had a good idea that I would just add it on the end because I wanted the modification to be used on all engines or at least as many as possible. I studied all the intakes and accessories I could and found some of the intakes go right over the top of the head and would hit the extension if it was carried up and over the top. The certified engines had the longest fins by the exhaust port but I felt I needed to try a few different lengths to get a comparison of how much fin area to add or subtract after testing. Looking around the shop I found  some .050 6061 left over from another project and using my cardboard patterns I traced out enough blanks to do the job. Then I cut them out with snips..... in a couple of hours I had a good start.
 A side note, within hours of my initial publication of the test results guys were talking about how to get the fins drawn up in some form of CAD and cutting them out on cnc machinery etc. I did it with snips in less than two hours from the time I had the brain wave until  the fins were on the table. Folks this ain't rocket science. Over the years I have come to notice that most people work harder at getting out of work. Remember, the dread of a job is almost always worse than the job itself.

I mounted the head on the table with the rocker arm studs through a 2x6. Oh, by the way, I had removed all the casting flash from between  the factory fins with a slitting saw in my mill. You just use a grinder or file or whatever works. Then I started on the fin by the exhaust port ( bottom). I just picked up a piece of .080 4130 steel I had in the scrap pile that matched the curve of the head and stuck it in between the fins after sanding it clean. Then I clamped the fin to the steel and fired up the oxy actylene torch. With a stainless brush I heated the head fin and scrubbed it good and then tried to get the brazing to work. The first head went pretty slowly, I had trouble getting the braze to take and the fins would crack off but I kept at it. In the picture above you can see the joint, to the left it looks good, in the middle it looks cold and to the right it looks, well, like crap. You want it to look like it does on the left.
 I finally figured out that heat was the issue, I wasn't getting it hot enough. Aluminum is an enormous heat sink, about as fast as I heated it, it seemed to wick away and I couldn't get the rod to stick right. On the last few fins of the first head I had a better grasp of what was going on and had better luck.
 I went home and checked the groups and Bob Hoover was on there shouting about Durafix, I thought what a coincidence it was that I had just started on this and Bob found out about it at the same time. I made a post on the group that I was doing a fin extension using Durafix and said to "stay tuned". That is where our relationship began, Bob and I. It was worth the effort just to get to talk to him by email ..... I miss you bud.
 I changed the game plane on head two. I installed the plugs and filled the chamber with water. I then started on the bottom again but this time I turned the torch up and as soon as the head finned showed evidence of  accepting the rod I began to move around the fin like before but I concentrated the heat on the head and the filler would just flow around the joint like solder. It takes a lot of heat guys and done properly it only takes a few minutes. I could do two complete fins in about five minutes if all went well and then I would take a break and refill the chamber with water. I did the second head in about four hours.
 When you glue these on it doesn't have to be pretty. Only one joint will be seen but you need to keep the slot open for airflow. How? Just get a grinding wheel for non ferrous metals or a file and clean it with a wire brush when the grooves get clogged. A rough surface will cool better than a smooth one anyway.



Finished product

After getting the fins on cut wood strips to go in between them all and lay the head down like above. Use a sander to dress up the outside of the fin to remove burrs and make them all even. I didn't spend all day fitting each individual one perfectly, just cram something in for support to keep from breaking the fin off. The top four fins are under the exhaust port and I eliminated them before I mounted the heads on the engine.

 Change of subject now. Back up, back up, back up! Computers are nice but when a drive crashes it is a bad day.  About a month ago I had a real real bad day. My computer crashed and with it all my pictures. I have come up with these from all over where I have published them before, if I had only backed up. I'll try to locate more pictures tomorrow.   

 Wood spacers used for support to shape fins to the final form. The top 4 fins were removed before the heads were put in service. Thanks to Kevin McCune for finding my picture in his files.

I reground the exhaust valves, just touching them up in my grinder . DO NOT REUSE EXHAUST VALVES. I knew these heads would be on the plane just a few hours as a test base to see where to go with the fin experiment so I took a chance and reused the old valves. Not a good idea.  The fixture for drilling the heads for bottom plugs is visible in the foreground on the mill. I reused it to insert helicoils in the stripped plug holes.