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

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. 

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.