Conquest .40 R/C

The Cox Conquest .40 and .15 family.

The serial number.

Overall view of the Cox Conquest .40 prototype.

Conquest .40 R/C (6.5 cm³)

Prototyped in 1976

A prototype of the front intake, Schnürle ported .40 Conquest R/C engine. Externally, it is a scaled up version of the Conquest .15 engine, having the same stylish design and the same horizontally split cylinder design. Both engines are shown together at the left.

My sample engine bears the number "X001". "X" probably for "eXperimental", 001 maybe a serial number. The crankshaft carries the number 142, maybe also a serial number? The crankcase finish is shiny, as cast, not sand or glass blasted as it would probably have been for the final production version. A muffler similar to the .15 design can be attached to the rear exhaust, but a tuned pipe would also nicely fit here.

The engine is a performance engine with the following main features:

  • sleek crankcase styling similar to the Conquest 1.5 engine
  • ringless aluminum piston in a chromed brass sleeve
  • front inlet with Perry R/C carburetor,
  • rear exhaust,
  • the crankshaft is supported by two ball bearings, and
  • the crank web is covered by an aluminum cover reducing crankcase volume.
Measuring my sample engine gave the following results:


bore 21.2 mm
stroke 18.4 mm
swept volume 6.495 ccm
0.396 c.i.


Exhaust port 147°
transfer ports 121°/127°
inlet timing 197°

The exhaust timing is fairly standard, so that I would not describe it as "hot" but well suited for muffler operation. It would be interesting to know, whether the "speed" version was built with the same timing.

My sample engine came with a Perry carburetor installed, which would also be the logical choice for this engine. Perry carburetors were widely in use during the 1970s and have also been used on the Conquest .15 RC. On the other hand, the crankcase would accommodate also a much larger diameter carburetor neck. In fact, a very crude brass insert ring is used in my sample to fit the Perry carburetor.

The unique two part muffler has a slotted restrictor tube. The sample is roughly finished by just sanding casting flash away.

Cox Conquest .40: view into bypass channels.

Cox Conquest .40: view into crankcase.
Conquest .40 C/L version.

The picture on the left shows a C/L version of the Conquest .40 (not from my collection). Comparing the casting of the crankcase of my R/C prototype with the casting of the C/L version as well as the raw castings shown below reveals a different shape of the web between cylinder base and carburetor stub. Obviously different sets of investment dies must have been used.

Conquest .40 castings on tree.

Typical casting tree of Conquest .40 parts.

Individual trimmed Conquest .40 castings.

Trimmed castings for a Conquest .40.

Last modification of this page: 21.05.18

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