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Building Tips and technical articles. => 1/2 A building. => Topic started by: Jim Roselle on November 04, 2013, 03:52:39 PM
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Came across this awhile ago:
(http://i.imgur.com/zFXvgxC.jpg)
The ridge on the glow plug mating surface of this #4 cylinder has been machined off. Piston fit is super tight.
I installed it on a tee dee with a timing shim between the cylinder and case and five glow head washers. Could not get it to start so I tried it on reed valve with a spring starter and only got mid 17k out of it with 18% nitro and a cox 5x3. Any advice on how to get the best performance out of this thing would be appreciated.
Thank you,
Jim
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Tee Dees and all Cox engines, after about 1950, seal at the bottom of the plug, not in the area you see as shaved. It should have NO effect on the engine.
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That's right. The super tight piston is a clue though. Unless the piston crown rises past the head landing, that timing shim isn't helping anything. Is another piston super tight? If so, then the cylinder must be out of round, assuming it's not a burr in the exhaust port, but I know you know that.
Rusty
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Tee Dees and all Cox engines, after about 1950, seal at the bottom of the plug, not in the area you see as shaved. It should have NO effect on the engine.
You're right, I wonder why the top of the cylinder was milled then?
Jim
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That's right. The super tight piston is a clue though. Unless the piston crown rises past the head landing, that timing shim isn't helping anything. Is another piston super tight? If so, then the cylinder must be out of round, assuming it's not a burr in the exhaust port, but I know you know that.
Rusty
It's not overly tight, just a good snug fit. I never put it back on the Tee Dee after I loosened things up on the reedie. I will have to give it another go on the Tee Dee.
Jim
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It's not overly tight, just a good snug fit. I never put it back on the Tee Dee after I loosened things up on the reedie. I will have to give it another go on the Tee Dee.
Jim
Is it tight all the way up the barrel or just an unusually tight pinch at the top? I came into the Tee Dees late in life(how unfortunate for me), and have only seen two brand new #4s in the Cox package, so that puts me completely in guessing territory now. I think some later ones are not even tapered. Now I'm just curious as to what you figure out about it.
I think Bernie's Tee Dee .049 replacements are pretty good if the fit is right, but I have yet to try one. I'd also love to have a spare #5, as I suppose a lot of people would. Like you, Jim I love to fly mine, not just look at them.
Rusty
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Is it tight all the way up the barrel or just an unusually tight pinch at the top? I came into the Tee Dees late in life(how unfortunate for me), and have only seen two brand new #4s in the Cox package, so that puts me completely in guessing territory now. I think some later ones are not even tapered. Now I'm just curious as to what you figure out about it.
I think Bernie's Tee Dee .049 replacements are pretty good if the fit is right, but I have yet to try one. I'd also love to have a spare #5, as I suppose a lot of people would. Like you, Jim I love to fly mine, not just look at them.
Rusty
Just a really tight pinch at the top. I matched up a set yesterday that was pinched so tight it wouldn't start without a timing shim to keep the piston from going all the way up. Ran 2 rich extra castor ounces through like that to loosen up the piston then ran it without the shim, rich and oily. Going to fly it today, should be a real screamer.
Jim