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O.S. Speed B21 Drake AD3 .21 Nitro Engine
- $223.56
- Brands O.S. Speed
- Product Code: OSM1CJ00-1
- Availability: In Stock
O.S. Speed B21 Drake AD3 .21 1/8 Nitro Engine with EBIS Break-InThe O.S. Speed B21 Drake AD3 .21 Nitro Engine is a competition-focused powerplant developed in collaboration with Adam Drake for 1/8-scale off-road racing. Designed as an evolution of the B21 AD2, the AD3 combines a revised crankcase, optimized cylinder porting, a DLC-coated crankshaft, and a lighter cooling head to produce strong low..
High Performance 1/8 Scale Nitro Engine with EBIS Break In
O.S. Speed B21 Drake AD3 .21 1/8 Nitro Engine with EBIS Break-In
The O.S. Speed B21 Drake AD3 .21 Nitro Engine is a competition-focused powerplant developed in collaboration with Adam Drake for 1/8-scale off-road racing. Designed as an evolution of the B21 AD2, the AD3 combines a revised crankcase, optimized cylinder porting, a DLC-coated crankshaft, and a lighter cooling head to produce strong low-end torque, smooth power delivery, and a broad usable RPM range.
This version includes EBIS break-in service, giving racers a professionally prepared engine that is ready for the next stages of tuning and track preparation.
Key Features
Adam Drake Edition 3 competition engine
Designed for 1/8-scale buggy and truggy racing
3.49cc / .213 cu. in. displacement
Semi-long-stroke configuration
Redesigned cylinder liner with optimized porting
Adam Drake-specific cylinder design
Boost-bypass crankcase design for smoother throttle response
DLC-coated crankshaft with larger double tungsten counterweights
Updated backplate with integrated thrust plate
Lightweight, low-profile cooling head
21J slide carburetor
Blue anodized carburetor reducers for setup flexibility
Steel front bearing and ceramic rear bearing
Includes EBIS break-in service
Adam Drake AD3 Competition Design
The B21 AD3 was developed with input from Adam Drake and incorporates several changes intended to improve drivability and race performance.
The crankcase uses a boost-bypass design that helps create a smoother transition through the RPM range. Combined with the redesigned cylinder liner and optimized porting, the engine is intended to provide responsive low-end power while maintaining strong output at higher RPM.
Its semi-long-stroke configuration and larger double tungsten crankshaft counterweights further contribute to the engine's torque characteristics and smooth power delivery.
Lightweight Cooling Head
The AD3 uses a redesigned cooling head that is approximately 3 mm lower and 14 g lighter than the previous design. Reducing weight higher on the engine helps lower the overall center of gravity, which can be beneficial for handling on a competition buggy or truggy.
The head features a distinctive black-and-blue anodized finish associated with the Adam Drake edition.
An O-ring is also incorporated into the inner head to help reduce vibration and improve resistance to dust entering the combustion area.
DLC Crankshaft and Updated Backplate
The crankshaft features a DLC coating and larger double tungsten counterweights. This construction is designed to provide smooth operation and support the engine's performance across its operating range.
The rear cover/backplate incorporates a built-in thrust plate to reduce friction between the connecting rod and backplate. This design also helps reduce wear and is intended to contribute to longer engine life.
21J Carburetor and Reducers
The AD3 is equipped with an O.S. 21J carburetor and includes interchangeable carburetor reducers for tuning the engine's airflow characteristics.
The standard AD3 specification includes:
6.5 mm reducer – recommended for buggy applications
7.5 mm reducer – recommended for truggy applications
This gives racers an easy way to adapt the engine's response to the vehicle and track setup.
EBIS Break-In Service
This version includes EBIS (Engine Break-In Service) rather than being supplied as an untouched, unbroken-in engine. The Drake Racing product information specifically lists the AD3 as available with or without break-in service, while retailers also identify EBIS/Adam Drake break-in versions of this engine.
Because break-in service is performed before delivery, the buyer should follow the seller's specific instructions regarding initial running, fuel, tuning, and post-break-in preparation.
Performance and Applications
The AD3 is intended for demanding 1/8-scale nitro racing, particularly buggy and truggy applications. Its combination of torque, linear power delivery, and a practical operating range of approximately 4,000–42,000 RPM makes it suitable for racers looking for controllable power rather than an overly abrupt throttle response.
For the engine-only configuration, the manufacturer recommends pairing the AD3 with an appropriate tuned pipe and manifold. For buggy use, the TB02/2090SC pipe with a 75 mm manifold is listed as the first-choice setup. An 85 mm manifold can also be used for truggy applications.
Product Specifications
| Specification | Details |
|---|---|
| Brand | O.S. Speed |
| Model | B21 AD3 Adam Drake Edition 3 |
| Engine Type | .21 competition nitro/glow engine |
| Application | 1/8-scale buggy and truggy |
| Displacement | 3.49 cc / 0.213 cu. in. |
| Cylinder Configuration | Single cylinder |
| Bore | 16.4 mm / 0.646 in. |
| Stroke | 16.55 mm / 0.652 in. |
| Output | 2.65 PS / 2.61 HP at 34,000 RPM |
| Practical RPM Range | 4,000–42,000 RPM |
| Carburetor | 21J |
| Crankshaft | DLC-coated, double tungsten counterweights |
| Stroke Design | Semi-long stroke |
| Front Bearing | Steel |
| Rear Bearing | Ceramic |
| Cooling Head | Lightweight, low-profile Adam Drake design |
| Carburetor Reducers | 6.5 mm and 7.5 mm |
| Engine Weight | Approx. 350 g / 12.35 oz |
| Break-In | EBIS break-in service included |
Specifications are based primarily on The Drake Racing's AD3 specifications, with supporting product data from O.S. Speed/retailer documentation.
What’s Included
O.S. Speed B21 AD3 Adam Drake Edition 3 engine
21J carburetor
Blue anodized carburetor reducers
Engine-to-header gasket
O.S. Speed P3 gold glow plug
EBIS break-in service
Note: This listing is for the engine with EBIS break-in. A tuned pipe and manifold are not included unless specifically stated by the seller as part of the package.
Why Choose the O.S. Speed B21 AD3?
The B21 AD3 brings together Adam Drake's competition-oriented engine development with O.S. Speed's precision manufacturing. Its boost-bypass crankcase, optimized cylinder, DLC crankshaft, low-profile cooling head, and ceramic rear bearing are designed to deliver a combination of strong torque, smooth throttle response, and reliable high-RPM performance.
With EBIS break-in service included, this version is particularly appealing to racers who want an AD3 prepared for the next stage of installation and track tuning rather than starting with a completely unbroken-in engine.
