Cylinder Head Specialists
308 Performance Heads

Holden 308 HP Camshaft & Cylinder Head Matched Kits

All of our cam and head kits have had many hours of research and development time as well as many hours of actual dyno testing. These kits are designed to be compatible with each other ( not mismatched or guessed ).

We have endeavoured to keep the original carb and manifold as we consider this to be very good.

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We have developed a true high performance 308 Holden Cylinder Head suitable for fast street strip type application. Suitable for unleaded fuels these heads are original castings that have been extensively modified as follows: 

  • All heads are chemically cleaned and magnaflux crack tested 
  • 16 new Bronze Guide Liners are fitted 
  • Hardened ex seats are fitted 
  • Larger inlet valves are fitted 
  • Ports are modified to suit 
  • Chambers are modified and polished 
  • Valves are new tuffrided steal ex with new Manley Race Master stainless inlet valves assembled with new seals and high performance springs. 
These heads have gone through hundreds of hours of flow bench and dyno time and flow more air than B Casting L34 and late model VN on high port castings.
Priced at NZ$$1595.00 + GST Complete.

All of these kits are designed to run stock rocker gear, although rollers can be used up to 1.6 ratio. 

More HP gains can be had as the heads flow enough air support about 420 HP but in most cases, it will effect bottom end power. Our aim is to produce ultra responsive street / strip kits using mostly stock parts. Flow figures are available, all our dyno testing was on the same stock short block at 9.6 - 1 compression ratio with stock carb and manifold. We found the stock carb and manifold to be a very good combination, we also found some pretty horrible results using some after market manifolds. 

The dyno tests shown are only a few from well over 120 actual tests performed. A point worth mentioning is our test engine for the stock heads and camshafts was also 9.5 - 1 compression ratio. From our experience most stock engines are more in the area of 8, 8.5 - 1 compression ratio. If this was the case the gains we got would be a lot greater but for our own test reference we want to know the exact gains, extra airflow and camshaft would make. All testing was done on our own fully computerised Dynamic Test Systems Dyno and corrected back to SAE standard figures. Testing was done on automatic sweep test mode. 

Test #1 Head Comparison
Dyno Test #1 - Click to Enlarge
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The first test shows our heads compared to stock, no other changes ( yes even stock cam ). We recommend you do not use the stock cam, as it is a very lazy acting profile and will not fully utilise the airflow potential of our heads. The dyno graphs will help you determine the camshaft to suit your needs or if you are unsure contact us for technical assistance. Remember all tests made more power everywhere than stock so there is no downside. Whether this is a tow car or race car there is a package to suit.
Test #2 - HP1-206 Kits
HP1-206 Kits. Heads as above with this camshaft will make more horsepower everywhere, will idle better than stock and will be very responsive on the throttle. Good low down mid range power, excellent towing or high diff gears with big diameter tyres. Our stock short block test engine made 280 HP - 350 ft lbs. of torque with stock carb and manifold. Dyno sheet below as compared to stock.
Dyno Test #2 - Click to Enlarge
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Test #3 - HP1-224 Kits
HP1-224 Kits. Heads as above with this camshaft will make more mid range to top end than the HP1-206 kits. It will have a slight high performance idle more suited to manual or auto with higher stall and lower diff gears. This kit made over 360ft lbs of torque and 332 HP on the same stock short block, original carb and manifold. Check out the graph compared to stock.

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