New Zealand Classic Car - - Technical Feature - Jaden Martin Pho­tos: Supplied

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.

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