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Holden High Compression ROAD RACER Inline 6 Blue/Black 12 Port Alloy Cylinder Head (Assembled 48cc)

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ACHA 33C48
11.50 KGS
Calculated at checkout

Product Description

New Yella Terra high-compression, closed chamber alloy cylinder head. Based on the successful Stage III Bathurst 6000, popular amongst revheads, racers and endorsed by the Bathurst legend Peter Brock.

Now exclusively designed for use with 202 ‘Blue’ & ‘Black’ VC-VK 3300cc engines. Revised quench pad now promotes a much cleaner and consistent burn - forcing the air/fuel mixture toward the spark plug on the compression stroke for improved power and economy! The desirable ‘kidney’ cnc cut chamber (similar to the 161), caters for higher compression ratios without excessively milling the deck face and whilst retaining critical piston-to-valve clearance in high lift/cammed and or stroked engines.

Producing a whopping 240+ potential horsepower out of box! Thick port walls ideal for further specialist modification. Can be retrofitted to ‘Red’ 149-202 engines with very little modification to engine block.

Ultra lightweight alloy casting with re-designed water jackets for much improved head cooling and more regular metal sections for resistance to cracking. Revised port designs for a 30% improvement in flow figures. Yella Terra developed computer controlled machining of entire head guarantees consistency, reduces valve shrouding and equalises combustion chamber volumes. Oversized diamond honed valve guides for accuracy and controlled lubrications, allowing for a range of aftermarket valves.

Revised port shape giving approximately 15% more power. Fitted with exhaust valve seat inserts of average 30% harder cast iron than original units which in standard form are prone to high rate of valve seat wear - the most common cause of failure. Punch some life into your 6 with Yella Terra!


Technical Specification

Material: AS 601, 356-T6 heat treated aluminium
Assembled Weight:


Assembled CC Volume:




Intake Runner:

Exhaust Runner: 71cc
Intake Valve: 1.740"
Exhaust Valve: 1.480"
Valve Guides: Solid Brass 
Inlet Valve Seats:

Cast iron 1.812"x0.250"

Exhaust Valve Seats:

Lo nickel chromalloy 1.625"x0.250"

Spark Plugs: Tapered seat
Deck Thickness: 0.450"
Installed Height: 1.520"
Rocker Post: Machined for 7/16" screw in stud

Spring Seat OD:

Assembled Part No. ACHA33C48

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