Actually I reduced the number of fins by one per cylinder, reduced the compression to about 8.0 to 1 with copper head gaskets and did a three angle valve job. I still have good cooling and the engine seems to make equal power compared to the other heads with the lower compression ratio even though the density altitude is much higher now. Stay tuned.
Hi Lucas, the long and short of it is yes, something happened to the originals. When I began expeimenting with the fat fin mod I used a set of heads that had been cooked for 60 hours and had the bottom plug holes stripped. I installed helicoils and brazed on the fins. I even used the old exhaust valves.
The exhaust valve on #2 would not stay adjusted from the first start up, it kept getting tight but everything else worked very well. I had a few fins crack loose on the other head but all went well until about 11.8 hours when I decided to pull the head and investigate the valve issue. When I pulled the head it was cracked between the intake and exhaust port, around a plug and the the seat was loose all problems I blame on the past heating issues. None of the other valves needed any adjustment. I had a set of GPASC heads that had been rebuilt and I decided to use the info gathered from testing the originals to make a slightly modified version. I have to say that the fat fin mod is a huge success even though I have only 11.8 hours of testing. I did not want to use a good set of heads for the original test so that is why I used the old junk heads. I didn't want to be out a ton of cash it turned out to be a flop.
If you are interested get back in touch with me in a few weeks and I'll let you know how the new ones work.
Lucas, I used some stuff called Durafix. No flux. There are some videos on you tube about using it. I have a $3500 tig welder but I wanted to try this stuff so a dude in his garage could do it. So far it has worked well. If you decide to try it let me know and I'll give you some pointers. I have documented this extensively on the AirVw and Aeroconversions groups on yahoo. "Fat Fin Head" is the name of the thread. I see you are a welder so you might be better off tig welding them or mig with a spool gun but without a doubt you should do the mod. Look at my numbers on the groups. I've had all kinds of trouble with temps, until I did the mod. Read all you can and you decide for yourself but I can tell you without question you will glad you did it. BTW, I use mofoco 042 also and they are hands down better than the 042 chinese stuff from Great Plains. I tried em both.
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