One of the areas that separate the “backyard” engine assembler from the professional engine builder is attention to detail. In a racing application it is more important to stack small gains together for increased performance. These gains generally come from the detail work that can only be accomplished by true machinists with the proper equipment.
One area long overlooked has been the importance of the valve job. Traditionally the professional engine builder would use equipment from either Serdi or Sunnen for this work. But, the single point technology now availablehas taken an ordinary valve job to much higher performance standards.
Our shop utilizes the Newen Contour BB for all valve jobs. The Newen allows us to accurately machine combustion chamber shapes, complex radiuses, valve seats, and port throats all in one machining operation. A computer controls the position of a single point cutting tool in the work head, netting the finest valve seat concentricity and finish in the industry today.
These qualities are crucial in any application but, as more and more of the sanctioning bodies utilize spec head rules the valve job becomes even more important.
And here is why…
The lapping of powdered metal valve seats, or of some cast iron valve seats, brings about unavoidable “chatter marks” . Chatter marks are very harmful to a valve since gases escape through them while the valve is shut.
The machined valve seat will consequently deform rapidly and its seal will never be adequate. Chatter marks result from carbide form tools scrapping a large surface of a material with a grainy structure made of different materials such as powder metals, nodular cast irons etc.
Traditional valve seats machined with form tools all present undulations measuring hundredths of millimeters that are the direct result of irregular cutting efforts on a 360 degree rotation.
These undulations inherent to the very principle of machining with form tools, have unquestionable consequences on valve sealing and require further lapping of each valve on its valve seat to obtain an acceptable seal.
With the single point technology afforded us in the Newen equipment, micro-chatter marks and undulations are virtually impossible to generate. Single point machining does not allow the formation of such defects. Much like machining on a lathe, machining with a turning tool traveling on two interpolated axes generates a circular micro-groove, perfectly round. The depth of the groove and the interval between 2 grooves is controlled by the numerical control of the machine. This yields the finest achievable surface finish.
We have utilized this technology for years now with great results. Our shop understands the importance of a really good valve job and how it relates to performance but, at over $100,000 for the equipment, most shops won’t pony up. These are details that make the difference in the final product.