Cylinder Head Modification services since 1968



Kelford Cams has two very experienced cylinder head technicians and can offer cylinder head development that matches, or often betters, anything available in New Zealand or offshore. In fact because of our multi-valve cylinder head experience, customers worldwide are sending cylinder heads to us for modification. Recently we have had development projects for customers from Jamaica, Hong Kong, U.A.E., Malaysia, Australia, U.S.A. and U.K. 

We have over 30 years of combined experience with cylinder head modification. We have spent thousands of hours testing and developing successful port & chamber designs for all types of engines and for all types of motor-sport applications. 

All of our cylinder heads are modified to suit your specific application. Often one size will not suit all, so our engineers will work with you to come up with a cylinder head, or cylinder head and camshaft configuration that suits your needs.

We will at times publish airflow figures, however many years of measuring port velocity and comparing velocity numbers (and port areas at specific locations through the port) with engine performance gives us a much better result than just using a flow bench to generate CFM flow numbers. Our valve angles and seat designs are also tailored to each application. Again we draw on experience and testing to create valve seat shapes to optimise the flow curve and to suit the application. Our valve seats are cut on New Zealand's only NEWEN CNC valve seat machine.



Stage 1,
This is the minimum level of modification available. We optimise the cylinder head using stock valves. We use the NEWEN CNC seat machine to modify the valve seat shape for good gains in airflow, especially at low valve lift. This level of modification suits fast street and mild racing applications. Your cylinder head is acid washed, pressure and hardness tested. The head is then ported to maximise airflow using the reshaped standard valves and the valve seats are cut and reshaped to our own design. The head is surface ground to the correct surface finish and to achieve the correct combustion chamber volume for your application. Then the head is final washed and assembled with new stem seals and high performance valve springs to suit the application.

Stage 2,

This level of cylinder head modification suits well built, high performance engines for extreme street, drag, drift, circuit, rally, and most racing applications. Your cylinder head is acid washed, pressure and hardness tested. The ports are modified to suit your application and to suit oversize stainless valves, (inconel valves are used on exhaust in turbo applications). The valve seats are cut to our design on the NEWEN CNC valve seat machine. The head is surface ground to achieve the correct combustion chamber volume for your application and to the correct surface finish. The head is flow tested to verify CFM and velocity improvements. After final washing, the valves are installed, stem seals fitted, spring heights set and springs assembled. The valve springs supplied will be chosen to suit your application, cam choice and RPM. We only use the highest quality valve springs in these applications.


Stage 3
Stage 3 heads are absolute full effort custom builds, often requiring port and chamber re-design, offset valve guides, filled ports, custom made

titanium valves, complete valve train system analysis and design etc. If you are racing at the top level and want to leave your competitors behind, have a chat to us and find out what we can do for you.



we uSE the best equipment for high performance valve seat machining


  CLICK HERE:  to see a video of how this works.




 ProbenchWe have been testing port velocity for 13 years. It's now a whole lot easier on the computer controlled digital readout Superflow 1020 Flowbench.




Recent cylinder heads we have supplied to worldwide racers include...

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 ... all of which have custom developed Kelford camshafts.


For further information click here to contact us .

WE ARE New Zealand agents for CHI cylinder headS AND MANIFOLDS.CHI 

Ford Cleveland and Chrysler Valiant 245-265 Hemi aluminium cylinder heads and manifolds. Home of the world famous 3V range of high performance cylinder heads to suit everything from mild street engines to top competition engines. Go to or call us for info on these very clever cylinder heads.

Kelford Cams was chosen to supply these heads to NZ customers because we understand customer requirements when it comes to cylinder head and valve-train compatibility and the integration into the the entire engine build to achieve the correct performance in the given application.

CHI cast iron and Aluminium cylinder heads


Stan Weiss Cylinder head flow figures database

 Stan has put together airflow figures from head porters and head manufacturers from all around the world, this is a great referance site. You will find a lot of our ported heads listed here.

Click here to view Stan's database of cylinder head airflow figures for all sorts of applications.