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Are the jewel box engines the good ones Empty Are the jewel box engines the good ones

Post  batjac Tue Dec 13, 2022 12:19 pm

We all know that as the Cox company passed from group to group, the packaging changed, and the quality changed. I have a jewel box TD .049 engine N.I.B. and was wondering if this is one that has the tapered cylinder and good fit. The last TD engines Cox sold before ending production were just thrown together without the quality of the earlier engines. Since these last engines came in the cardboard boxes, I do not know when Cox stopped using the jewel cases. I am hoping that the .049 I have is the tapered fit, since I want to use the engine for a club 1/2A contest next season.

The Trepidatious Mark
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Post  balogh Tue Dec 13, 2022 2:27 pm

Mark,

If your crystal box TeeDee has a stepped wsll cylinder, chances it has tapered bore are high..Thick wall cylinders in my TeeDee collection have no taper bore..even some of the stepped wall cylinders have no taper bore..looks like taper bore discontinued earlier than crystal box package..

If your TeeDee has thin wall cylinder, that is surely a taper bore..if the venturi is with no screen and the crankcase has no No2 stamped on the mounting beam, then it is a taper bore cylinder, most likely with an oiling hole on the big end of the conrod..

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Post  batjac Tue Dec 13, 2022 6:28 pm

It's a stepped cylinder. That portends good things.

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Post  balogh Wed Dec 14, 2022 12:54 am

Mark, the best way to check is dismantle the engine. Below is my jewel box TeeDee from '75 (see the Litho mark on the Instruction sheet) with stepped wall cylinder and its piston easily passing the TDC, meaning it is non taper...this is why I assume, taper bore may have discontinued earlier (around '74 I guess) than jewel box.

Are the jewel box engines the good ones 16710010

Mass produced, old-stock engines like Black Widow still had taper bore in 1973, like mine, which is a first production run BW, with the red rubber spinner and stepped wall cylinder. (BW production started in 1973.) Later produced production engines and high end TeeDees had no taper bore, I guess.

Venom and Killer Bees in short production run also reverted to taper bore, as a means of making them more attractive in years when business began to decline, but their production numbers may have been much smaller than TeeDee-s.

So I guess if there is a Litho mark on your instruction sheet from no later than 73-74, chances for taper bore are good. But removing the cylinder and pushing the piston up by hand will tell you the truth.
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