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Cox Engine of The Month
October-2017
MauricioB's

"Cox Medallion .049 R/C"



PAST WINNERS
Speed Contest 2018
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Choosing a cylinder for an engine is not always that easy that is if you are looking for performance.
Here is a chart of Cox cylinders and their numbers.
(These are all .049/.051 cylinders)
Number
Description
 1 Used on early Black Widow and 290-291 series engines. 2 bypass, sub-piston induction, some cylinders had milled top fins and some older ones didn't.
 2 Used on Golden Bee and older Babe Bee engines. Single bypass, sub-piston induction, top fin not milled.
 3 This number was used on lots of different cylinders. The Venom used a #3 (or 4, see below) cylinder that was 2 bypass, 1 booster, sub-piston induction, tapered, top fin milled.
 4 Used on T.D. .049 engines. 2 bypass, 2 booster on each bypass, each with 3 separate milling cuts, sub-piston induction, top fin milled, has tapered grind. Sometime in the 1980s, TD cylinders were no longer tapered. This number has also been seen on the Venom .049 which is a 2 bypass, 1 booster, sub-piston induction, tapered, top fin milled.
 5 Used on T.D. .051 engine. 2 bypass, 2 booster on each bypass, each with 3 separate milling cuts, sub-piston induction, top fin milled, has tapered grind.
6
Used on QZ and QRC and seen on some Sure Start engines. 2 bypass, no sub-piston induction, top fin milled. NOTE: The Sure Start cylinder had a twin slit exhaust, 1 booster on each bypass and no SPI
 7 Used on many engines: product engines, car engines, Sure Start engines, Single bypass, sub-piston induction, top fin milled. (Sure Start had 1 boost port on each bypass)
 8 Product engines and car engines. single bypass, narrow exhaust, no sub-piston induction, top fin not milled.
9
Very rare, not much known, seen on some product engines
 0 Used on product engines, 2 bypass, no sub-piston induction, top fin milled.

 P-40 Used on the "Super Bee" .049 engine, came on the ready-to-fly P-40 planes 1959 through 1961. 2 bypass, sub-piston induction, top fin not milled.

Slit Cylinders
 Description
 (note: some engines such as Black Widow, QRC, Medallion... had slit cylinders on later models)
Sure Start
2 bypass ports, 1 boost port on each bypass, top fin milled, no SPI
 Babe Bee
 2 bypass ports, top fin milled, no SPI
 Texaco
2 bypass, 1 boost port on each bypass, top fin milled , no SPI
Killer Bee ('92-'01)
 (.049/.051) 2 bypass, 1 boost port on each bypass, top fin milled, has SPI, has tapered grind.
Killer Bee (post '02)
2 bypass, 1 boost port on each bypass, top fin milled, has NO SPI, no tapered grind.
 Medallion
2 bypass, 1 boost port on each bypass, top fin milled. no SPI (RC version ground for use with throttle ring)
 NFFS Medallion .051
.051, 2 bypass, 1 boost port on each bypass, top fin milled, no SPI
 Dragonfly
 2 bypass, 1 boost port on each bypass, top fin milled no SPI
 RC Bee
2 bypass ports, top fin milled, no SPI (ground for use with throttle muffler)
QRC
2 bypass, top fin milled, no SPI
 Cast Crank Sure Start
2 bypass, 1 boost port on each bypass, top fin milled, no SPI
Black Widow
2 bypass, 1 boost port on each bypass, top fin milled, no SPI

 Early Engine Cylinders (No Number)
Description
 Space Bug
2 bypass, open exhaust, has SPI, top fin not milled
 Space Bug Jr.
 1 bypass, open exhaust, has SPI, top fin not milled
 Thermal Hopper
2 bypass, open exhaust, has SPI, top fin not milled
 Strato Bug
2 bypass, open exhaust, has SPI, top fin not milled
Space Hopper
 2 bypass, open exhaust, has SPI, top fin not milled
Babe Bee ('56,'57)
1 bypass, open exhaust, has SPI (may appear to have very little to no SPI depending on piston type), top fin not milled
 Golden Bee ('57)
 1 bypass, open exhaust, no SPI (may appear to have very little SPI if the piston and con rod connection is loose), top fin not milled
RR-1 ('57)
 2 bypass, open exhaust, has SPI, top fin not milled


Porting Examples


Cylinder Style Examples



From top to bottom, left to right.
[SureStart slit cylinder], [#7 open exhaust cylinder, ground for use with muffler, throttle muffler or throttle ring], [Black Widow open exhaust cylinder],
[step cylinder and throttle ring, cylinder ground for better fit of throttle ring]



Thinner style cylinders can be found on engines made before the 1970s. They can run much cooler due to their thin walls. But can be damaged more easily when removing/replacing or in a crash.



They are both #2 cylinders, the one on the left (the average one) is off a 1978 Babe Bee and the one on the right (the thin one) is off a 1962 Babe Bee.


Non .049/.051 Cylinders
(coming soon)


Tee Dee .010
 
Tee Dee .020
 
Pee Wee .020
2 bypass ports, open exhaust,  top fin may or may not be milled depending on age, may or may not have SPI
 Tee Dee R/C .050
 
 Queen Bee .074
 
 Tee Dee .09
 
Tee Dee .15
2 bypass, 2 booster on each bypass, each with 3 separate milling cuts sub-piston induction
 Special .15
 
Special MkII .15
 


In Feb of 1956, Cox switched over from the small diameter cylinder/head threads to the current size.





If you spot any issues at all on this list, PLEASE let me know! It would really help!