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Engine basics => Engine set up tips => Topic started by: frank mccune on June 05, 2015, 05:38:51 PM
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Any Old Timers out there?
I have one a couple of those old Stunt .40 Fox engines that I dug out of the attic to use. After a careful break in I am using one in a Magician with an 11-5 wooden prop. ST nva, RC Long plug, and10% fuel with 28% castor oil.
The 4-2 break is not crisp and clean but seems to be slow breaking into one or the other. I have been told that an extra head gasket is the answer. The engine is a dream to start and needle but so far, the perfect 4-2 break alludes me. I have been informed that this engine was designed for Stunt by George Aldridge so the timing must be correct. Perhaps a profile is not a good place to search for that good Stunt break.
Any suggestions?
Tia,
Frank
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Hi Frank,
I have run a few of those, and always had to take a pretty good while to get the tank height correct on a profile. No problems in a built up fuselage/inverted engine. From what I remember the last profile I used one on, the tank was set about 3/16th" high. Had a lot of flame outs inverted until I got that fixed.
BIG Bear
RNMM/AMM
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Hi Bill:
Thanks for the reply.
This Magician has the tank, a four ounce wedge, inlet into the fuselage so that about 1/2" is projecting on the outside of the body. I have never seen a profile plane where the tank is installed into the nose. The tank is on centre line of the engine and is uniflow. I have not had any problems with the engine going inverted. The engine runs a constant 4 cycle except near the top of a loop etc. when it breaks into a 2 cycle. Being newer to stunt, I am going to leave the engine as is as it appears to everything that I need from an engine. I know that I will grow weak and have to add an extra head gasket to satisfy my curiosity. Lol
Be well,
Frank
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I might be completely off base, Frank, but Randy Smith's tips at the top of this section suggests you might be a little under propped, based on your description. Maybe try an 11-6 or a wide blade prop to load the engine better and get better 4-2-4 breaks.
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Hi Bill:
Thanks for the tip. I will make that change. It is a bit easier to change props than it is to add a head gasket! Lol
This engine is one of those good Fox products. I bought it many years ago and broke it in very carefully. It was in storage for at least three decades and when I put it on the test stand, it started first flip. It still starts flip. I am holding my breath hoping that it will not wear out" very quickly. It is a pleasure when you have a good handling engine! I have a ton of parts to keep this engine running for a long time. As a matter of fact, I bet I have at least one extra engine in the attic.
Be well my friend,
Frank
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Hello BB:
You're correct! Why the constant search for perfection. I should just enjoy what I have!
Be well,
Frank
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You're correct! Why the constant search for perfection. I should just enjoy what I have!
It should, however, be pretty amenable to *small* tweaks, and if nothing else, if you are careful, you will learn something. The weak/slow break is a classic sign of either not enough oil, or not enough compression ratio. A *very small* (like a .003 thinner head gasket) should have a minor but detectable effect and improve the sharpness of the break. Either that, or add 3% castor to the fuel, and see what happens. Be careful to control the other conditions and observe carefully.
Brett