PRECISION- BUILT ENGINES
CNC M ACHINING
In previous issues, we’ve taken a good look at the more traditional ways of machine work when it comes to rebuilding an engine, using manual measurements and machines, but we wondered how the industry has evolved as technology has progressed in recent years. With that in mind, we discovered how, with the help of computer-numerical-control (CNC) machines becoming a staple in many shops, the way the job gets done has vastly improved. To find out what that means for your end product, we caught up with the team at Henson and Murray Engine Rebuilders (H&M) to ask them a few questions and get the expert knowledge on the subject. H&M: ‘CNC machining’ is a process typically used in manufacturing that utilizes machine tools controlled by computers — things like lathes, mills, routers, and grinders. The machine tools function through
numerical control and the program can be customized to suit a specific task or object. This allows you to control features such as feed rate, coordination, location, and speed, meaning the computer can control exact positioning and velocity, too.
Traditional CNC machines function on a three-axis (X, Y, and Z) computer-generated 3D model of the item being machined, where parameters are inputted by the user into the machine’s control computer to undergo precise machining of components that would otherwise have been machined by hand.
So, for engine rebuilding, we use the RMC V80 CNC machine, which is big enough to do all but the very biggest of motors in New Zealand, and it’s the largest of its kind here. Already a true simultaneous threeaxis, computer-based, Cnc-controlled machining centre, we have also had a fourth axis enabled for extra precision. The main drawcard of CNC machining is that all work carried out is extremely accurate, as it uses the operator-inputted parameters, which are then Definitely. It is programmed with conversational technology to understand what the user wants, by asking questions about the information that has been inputted in relation to the job. A probing system automatically checks the work to confirm that the human input is valid, making corrections where required and confirming that the request can be completed without damage or error … it is capable of tolerances of 0.0001 inches, which, in effect, translates to longevity of the end product.
With the programming CNC [machining] uses, you can now re-machine to OEM [original-equipment-manufacturer] specifications. Many people with classic cars are looking to keep their engines as close to, or completely, original, so being able to remanufacture an old engine to its original specifications is important to them — not just for nostalgia but for doing it correctly while also increasing the value of the vehicle. as machining oversize liners, decking of the block, and interpolating the liner recesses on a Scania V8 16 block, for example, or probing [the] bores and decks of a small block Chev to give you all the necessary information prior to the boring and decking process. You can also do small and conventional CNC milling jobs.
One of the biggest differences is the accuracy of the align boring — traditional align boring used to be completed with a horizontal bar; however, this would require each main tunnel on the finished product to be checked and altered manually, as the bar had the ability to sag. With the new machine, each tunnel is completed independently, and, in this industry, accuracy translates to less wear and a longer product life.
Although it will do almost any jobs, we use other modern machinery for certain components — for example, valve grinding is completed in a purpose-built machine. Yes, we can, although not many jobs require this, as most components can be saved through re-machining or a new example ordered where it cannot be done. We tend to save this for when there is no other option — but it can be done, and this can aid owners of rare or harder-to-find vehicles in completing their project. This kind of work is the next stage in engine building. Over the last few years, we have used CNC machinery to build highperformance jetsprint engines, touring car race engines — we are the official NZ V8 Ute Racing Series rebuilders — hot rods, and restoration projects, which include superbike and production-bike engines.