New Yella Terra high-compression, closed chamber alloy cylinder head. Based on the successful Stage III Bathurst 6000, popular amongst rev heads, 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 equalizes 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!
- Excellent Flow figures:..240HP potential out of the box
- Average of .250” port wall thickness for custom porting
- Over 60% lighter than factor Iron Heads
- Flow over 30% better than the standard Heads
- Holden exterior design with totally revised ports and water jackets for improved cooling, reliability and performance.
- Hi-Compression 48cc Chamber
Note for Assembled Heads – Our Assembled 6 Cylinder heads are setup for .470” Max lift. If your engine configuration will exceed .470" lift at the valve, it is recommended you purchase our Alloy 12 Port head as a Bare 74cc or 68cc and source your own Valvetrain to your required specs.
TECHNICAL SPECIFICATIONS BARE HEADS
| Material: | 356 Alloy Heat treated to T6 |
| Chamber Volume: | 48cc - also available in assembled 72cc (Suit Forced Induction) & 56cc (Standard Compression) |
| Inner Runner: | 82cc |
| Exhaust Runner: | 71cc |
| Intake Valve: | 1.740” |
| Exhaust Valve: | 1,480” |
| Valve Guides: | K Liners |
| Valve Seats: | Inlet Cast Iron 1.812”x .250” / Exhaust Nickel Chromalloy 1.625” x .250” |
| Spark Plugs: | Tapered Seats |
| Installed Height with Std Valves and .060” Valve Spring Insets/Shims | 1.520” |
| Spring Seat OD. | 1.250 |
YELLA TERRA ROLLER ROCKERS TO SUIT:
- Yella Terra YT 5008 (1.5 Ratio - 7/16" Stud Mount)
- Yella Terra YT 5029 (1.5 Ratio - 7/16" Shaft Mount)
- Yella Terra YT 6312 (1.6 Ratio - 7/16" Shaft Mount)
- Yella Terra YT 6332 (1.65 Ratio - 7/16" Shaft Mount)
- Yella Terra YT 6371 (1.5 Ratio - 7/16" Shaft Mount)
* - With extensive CNC Porting can achieve over 300+ HP potential
