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The DOHC 4 valve per cylinder head is very well designed and suits forced induction applications due to the high percentage of exhaust to inlet flow, a short, semi pent roof combustion chamber (66 cc average in BA-BF Series), two small squish areas and a centrally located spark plug for fast and efficient flame propagation.

The FG “Swirl head” has a slight change to the combustion chamber design to promote swirl and as a result the volume is reduced slightly to 64-65cc. The heads respond to porting in a similar way to the earlier cylinder heads and as you can see, the swirl inducing port profile is limited to the inlet only - the exhaust port profile is the same as the early heads.

For 2014 we have available a number of new innovations – we upgraded our valve seat profiles to now include up to 7 angles and now offer a full 5 –axis CNC porting on our Stage 5 heads.

Valve springs are always a problem in forced induction OHC engines, as comparatively light reciprocating valvetrain mass usually means a short, light spring is fitted as standard equipment. This usually limits the number of valve spring options available, however we have 3 different springs available to suit almost every conceivable application - please refer to our valvetrain section.

Forced induction engines also need good quality valves, especially on the exhaust due to increased heat when running hydrocarbon based fuels. The OE high nickel exhaust valve (identifiable by the O forged in the head) is good for moderate performance applications and for extreme duty applications we have USA made single groove stainless valves with flash chromed stems and hardened tips. The hi flowing exhaust port also produces high exhaust gas temperatures, typically 200-300 degrees F higher than other turbo engines, which again highlights the need for an extreme duty exhaust valve.

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Most orders are dispatched before their estimated dispatch date displayed above. However on some occasions, delays may happen. If this happens, we will notify you straight away.

Some products may be shipped via our distributors within Australia, meaning that once the order is placed we forward the order directly to our distributor. Our distributor then ships the part directly to you.

We can not guarantee the stock count from initial order placed, however can provide a stock amount prior to an order placed. Please note, stock availability is subject to change.

Orders may be dispatched in Partial Shipments. Multiple parts in one order may be shipped from different suppliers within Australia.
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