We make alloy heads for Holden V8 engines, designed to give you maximum power from your engine. We also manufacture top quality iron heads for Holden Blue and Black motors giving superior reliability and marked performance improvements.
Bennett "HI-PORT" alloy heads for your '69-'86 Holden 308 - definitely not for the faint-hearted!
These new Bennett ABH 308-3 Hi-Port heads offer unbelievable horsepower potential right out of the box. They're designed specifically to allow the use of any inlet and exhaust manifolds currently available. Dave Bennett, Australia's foremost performance head designer , has, by raising the inlet ports dramatically improved the air flow of his highly acclaimed 308-1 heads, which are still available for more moderate applications.
The results of the new Hi-port design are phenomenal! MORE AIR = MORE POWER
The simple change from standard heads to these highly engineered aluminium units, when combined with complimentary components, will yield up to 39.5% more air flow and dramatically improve cylinder filling over stock heads. The result is significantly more power output from your engine.
There is an increase in air flow from the superior Hi-Port design. Potential horsepower is directly proportional to air flow.
ABH 308-3 heads come fully machined and finished, ready to assemble. Nothing could be simpler. They have been designed with considerable scope for specialist porting shops and engine builders to carry out their favourite modifications for even greater air flow.
The VN style asymmetric port Holden heads will be a popular choice for engine builders seeking maximum power from any Holden V8 engine. Now Yella Terra's design team lead by Dyno Dave Bennett have made major gains in flow and efficiency over cast iron VN heads with the release of the Asymmetric Alloy Yella Terra heads part number ABH 5000-9.
The intake and exhaust port design has been significantly improved in its "as cast" state and a greater amount of material is retained between water jackets for even more radical porting to be undertaken by race head builders.
Much care has been taken to straighten the flow path from manifold to valve and incorporate subtle improvements into the basic design such as careful blending of the metal around valve guides, moving the exhaust valve away from the inlet valve and straightening the exhaust port exit.
The combustion chambers are a "State of the art" design to promote the most efficient burn of the extra air and fuel delivered by the improved intake ports and effectively extract exhaust gases. They are fitted with 2% nickel inlet valve seats and hard LPG and unleaded compatible exhaust seats, (except for ABH 5000-9M see below).
Resulting improvements in head flow over standard VN cast iron heads and Bennett ABH 5000-9 heads can be seen on the accompanying graph. Significant further flow improvement has been gained by careful porting by cylinder head specialists as indicated.
Heads are available in three different stages. Complete ROAD RACER specification assemblies with Double Diamond Tufftrided stainless 21-4N 2.020" inlet and 1.600" exhaust valves, three angle valve seats, high lift double springs and Chrome Moly Retainers. Ready to fit to your engine. P/No ABHA 5000-9.
Alternative valve and spring combinations are available as extra cost options.
The heads are also available bare with unfinished valve seats fitted to allow cylinder head shops to perform their own seat finishing and modifications. P/No. ABH 5000-9
To cater for engine builders wishing to fit special valve seats for specific applications we provide castings without valve seat recesses or inserts. P/No. ABH 5000-9M
Machining of VN style inlet port injector nozzle relief is an extra cost option on all models.
The enormous power potential of Yella Terra VN Style ABH 5000-9 alloy heads can be adapted to pre VN style 308 engines with the fitment of aftermarket manifolds or fuel injection systems combined with a suitable VN style flat tappet or roller cam and VN style exhaust headers.
These heads require Yella Terra shaft type heavy duty race rockers, P/No. YT6313, and offer the added advantage of a 50% weight reduction over cast iron factory heads.
The Holden Blue and Black cylinder 12 port style head forms a good basis for performance engine build ups however the factory version is unreliable and prone to cracking.
Yella Terra redesigned the Holden 12 port head with improved water flow and superior quality material to resist cracking in both mild and high stress applications.
The Yella Terra 12 port has a greatly improved port design over the original GM head, delivering a 35% flow increase over the stock head with significant scope for further flow improvement through individual hand porting by professional head shops.
All Yella Terra 12 port iron heads are fitted with valve seat inserts making them perfectly suited to unleaded or LP Gas fuels. The heads feature huge 1.740" intake and 1.550 exhaust valves and performance double valve springs.
There is a choice of standard 56cc combustion chamber size and a large volume 68cc 'turbo' chamber for low compression supercharged and turbo charged applications.
See also: Cylinder head FAQs
