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Atlantic Specs

Historic Racing

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BDA, BDD (US version of BDA) 1600cc and BDG 2000cc, fundamentally have the same block and head dimensions. Internal bores, pistons, combustion chamber  volumes , valves and tract sizes are primarily where the differences are.
There are 15 variants of the original BD (Belt Driven) architecture with power ranging from 100 to 650 horse power.
BDA, BDD, BDG, BDM, BDT, Cylinder Block Specification
Beautifully manufactured with structural bottom end casting for superior Liner seating and rigid 'End Cap' placement. High Quality heat treated LM25 casting machined for 12mm head studs or 7/16 UNC/UNF. Alloy block only suitable for dry sump applications using short jackshaft. Our block uses 4 port oil pump design to more effectively oil crankshaft and cam by feeding oil directly into the main Oil Gallery on exhaust side.
BDD Stock height of block is 8.230 ins to suit 77.6mm stroke crank , 5.230 connecting rods, and 1.465 compression height pistons. Custom block heights available. Main cap stud material  817 M40, main caps machined from 080A15 material, ground finish cap to block face dowel located, 2 bolt custom ARP fasteners, 4 bolt steel main caps are available by special order. All blocks are designed to accomodate  BDT (high flow volume) and/or BDG/BDD type water pumps, both work well with the high thermal efficiency of new BDD and BDG Cylinder Head.

Cylinder Head Specification is provided as Big Valve spec at (no additional cost) with unique high flow internal tract design. Inlet port bore and throat design is specifically designed to promote swirl and to accelerate the fuel air mix via the "Venturi" effect just behind the valve seat. Exhaust port bore tract and Exhaust Header Flange placement are all designed to encourage  cylinder scavenging and to block exhaust reversion pulse from returning back into cleared chamber. All ports and tracts are CNC machined on a 5 axis machine at no additional cost to extraordinary repeatable tolerances. Internal casting of the cylinder head water jacket is uniquely drawn from the 600hp BDT Cosworth head design where engine cooling was critical to the even temperature of all cylinders and combustion chambers. Head will accomodate 9/32 (7.14mm) or 6mm valve "Colisbro" guides, one of the best guide materials, as used by Cosworth Racing. Valve seats are typically stainless steel with Berylium or other seat materials as an option.

Liners are high quality spun cast in Portugal. Liner material specifically selected to match more closely thermal expansion characteristics of LM25 alloy block. Available in bores from 81mm to 90.4mm. All Liners protrude .002-3 above block face (all liners no matter what material drop). 81mm liner has 3mm step at top of liner, while 90mm liners are straight sleeves.  Chrome liner is an additional cost. Ceramic coated bores also available, enquire about sizes. BDT 1800cc block is available with 86mm Nicasil liner, oil squirt jets and 4 bolt main caps.

Blue Sky Racing in collaboration with Cometic Gaskets has developed its own unique cylinder head gasket (ask for Blue Sky Part #) for all bores from 81mm through 90.4mm. Each engineering decision has been made to aid in the reliability and to enhance the ultimate power capabilities of the assembled engine. Cometic's new three layer MLS head gaskets has an optional HP ring added, this means you no longer need to 'O' ring a block in the future. The three layer stainless steel Viton coated head gasket is re-useable if you wish to.

For Valve and other Cylinder Head Specifications see below:

BDA/BDD, US Atlantic 1600cc engine

    BlueSkyRacing      BDD Cylinder Head Spec Notes   Valve Dia Stem Dia Length
Inlet Valves - Big Valve BDD Big Valve is standard spec for BSR head   1.275 ins  32.38 mm 9/32 ins   7.144 mm 3.945 ins   100.20mm
   Standard Cosworth BDA BDD spec Cam tray has 1.20 cam followers as original   1.220 ins  30.99 mm same same
Exhaust Valves - Big Valve BDD Big Valve is standard spec for BSR head   1.083 ins  27.49 mm 9/32 ins   7.144 mm 3.945 ins   100.20mm
   Standard Cosworth BDA BDD spec     1.00 ins    25.40 mm same same
Valves  sometimes measured valve seat to end, a reduction of .042 ins or 1.067mm.   
     BlueSkyRacing     BDG Cylinder Head Spec Notes   Valve Dia Stem Dia Length
Inlet Valves BDG Head to original Cosworth spec.   1.402 ins  35.61 mm 9/32 ins   7.144 mm 4.560 ins   115.824mm
Exhaust Valves BDG Head to original Cosworth spec.   1.202 ins  30.53 mm 9/32 ins   7.144 mm 3.945 ins   100.203mm
BDG Cam followers are available to suit long dick valves please specify your overall valve length (typ) 4.560  
Valve Guide 9/32 Valve Stem diameter ( 6mm available ) COSPRO BRONZE  guides fitted and reamed to 9/32  
Valve Spring Platform 0.5 ID, 1.25 OD Suitable for standard Cosworth or equivdual spring and platform,  
Valve Springs (Dual) Cosworth or Better (0.66 ID 1,25 OD) Dual springs available but not included with head pricing  
Valve Spring Retainer Steel, Titanium or Aluminium Suitable for standard Cosworth, not included with head.  

BDD and BDG additional Cylinder Head specification:

Combustion chamber volume: BDD, 28.0cc produces 12.0 compression ratio, mill head 0.020 raises comp ratio to 13.0. with approximately 0.042  Blue Sky Racing custom Cometic HP gasket, BDG chamber volume is 34cc.

Inlet  tract sizes:  BDD Inlet tract cast to 24mm CNC milled to 26.4mm (1.0394) finished smooth. BDG cast 24mm milled to 28.5mm (1.122) smooth. Blue Sky racing cylinder head is cut to a very unique inlet tract profile to boost the torque and power of the head, combined with unique valve profile and up to five angle seat cuts.

Exhaust tract size: BDD Exhaust tract cast to 23mm milled to unique 'D' profile 0.92 ins cross sectional area smooth finish, valve pocket CNC milled to match. BDG cast 23mm milled to 26mm (1.023). Unique alinement of the Exhaust manifold flange and other strategies will be employed to reduce exhaust reversion thus increasing the HP by 4 to 6%

Valve Guides: BDD valve stem diameter 9/32 or (7.144mm) typical. 6mm guides available. COLISBRO BRONZE material provides high lubrication, low wear and excellent oil control.

Valve Seats:  Typically stainless steel valve seats will be used though Berylium and other materials are available. When seats are installed they will be available with a single 45 cut or with three angle cuts. The seats are designed for up to a five angle cut, uniquely matching the throat and bore profile. The valve pocket is opened up to assist in the development of a venturi effect as the fuel/air mix transisions from the intake tract to the pocket to the seat and finally into the combustion chamber.

Spark Plugs: Standard plug is 10mm with 12mm as an option, 14mm is not recommended especially on BDG head with larger valves. 10mm helps prevent valve seat to plug thread cracking (common on old BD heads. The smaller plug leaves more metal and  many more options for the future should re-threading be necessary. A number of plug manufacturers, ie Champion, NGK and others now produce extensive heat range options for all three sizes.

Water Jacket cooling: The Blue Sky Racing head has a very unique internal cooling architecture drawn from the high power BDT 600hp twin turbo engine. The head is cast from LM25 alloy in England with a unique internal design identical to the high efficiency cooling required on the BDT. The result is a head which has a high level of thermal conduction resulting in more even temperature distribution across the head. This reduces hot spots within the head and produces less stress on the cylinder head gasket and other critical engine components. Running the head cooling system at 30PSI at the head will ensure efficient combustion chamber temps and optinum power production from all cylinders. This is a very important feature.

Question email  Gordon

PRODUCTS PAGE INDEX  (use pointer to jump to page)

Page 1: Blocks - Heads - Cam Tray - Followers - Valves - Springs - Throttle Bodies

Page 2: Pulleys - Belts - Idlers

Page 3: Jackshafts - Camshafts - Flywheel - Spring Retainers - Stem seals - Gaskets

Page 4: Studs/Bolts - Manifolds - Cam Covers - Oil Pumps - Water Pumps - Hardware

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