stunthanger.com
Engine basics => Engine set up tips => Topic started by: Gordon Tarbell on May 02, 2008, 08:37:57 PM
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I am running a clunk tank set up on my ST51 Pathfinder. I am getting a long (13 laps) run at end of tank. I need to shorten time of lean run. If I put less fuel in engine runs fewer laps in happy zone before going in to lean run. I am thinking of going to sintered bronze clunk pickup instead of chromed brass clunk with single hoes in end with slit across it. (sulivan six oz. round tank). I tried wedging out rear of tank at the end of the day today and all I got for my effort was two laps in happy zone and about 150 laps at 100mph. Net effect of moving rear of tank appeared to make it more difficult to draw fuel nedlled on ground to same launch rpm as previous flights (9300 rpm). Stands to reason since pickup is farther out from venturi. I am going cut down end of brass (existing) clunk to remove groove that cuts across the pickup hole or put in a sintered bronze unit. What say you guys of greater experience and or wisdom.
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Do you have it setup as a Uni-Flow?
It seems to me that the problem is the clunk is too big, and it starts sucking air while there's too much fuel left in the tank. I think the sintered bronze clunk would make the matter worse, because it would start sucking air sooner. D>K Steve
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I have in the past chucked the brass clunk into my drill and tapered it a bit more sharply, making a cone out of it so it gets into the corner better. Still I personally dont find 13 laps really a lot to worry about assuming you can get good starts. that allows you an extra lap between each manuever if the conditions are nasty and you need the breather.
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I spent the last hour cleaning the tank and converting to a uniflow set up with the air line running along side of the fuel pick up line(airline terminating about .400" from clunk end.)The two lines are tied togeather and still easily clunk in tank with gravity.. The airline (uniflowline?) is able now to be hooked to muffler nipple or just out side air so I have room to experiment. Will try muffler pressure first.
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Share what results you get after you fly it!
Terry
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I will findout Sunday at the meet in Woodland.