How to build a BTCC race engine

The great thing about writing a story on race engine building is the chance to get your hands dirty – except I don’t, because everything in Swindon’s engine shop is so clean. There isn’t time to help with an entire 45-hour build, but I do have a crack at a couple of crucial stages.

First off is checking the clearance on the crankshaft main bearings (which support the crankshaft in the crankcase) and on the big-end bearings (which attach the connecting rods with their pistons) to the crankshaft. This clearance is crucial. Too tight and the bearings could fail catastrophically, too loose and they would wear prematurely with potentially the same end result.

With engine builder Tiago Lopes instructing and watching my every more, I check the clearances with Plastigauges, which look like thin threads of plasticine. When a short length is laid across each bearing journal and its cap tightened to the correct torque, the Plastigauge gets squashed flat. Measuring its flattened width against a scale gives the clearance in the bearing.

ARP competition bolts are much stronger than standard ones, which aren’t up to dealing the massive forces exerted in a race engine. I follow instructions to the letter, doing everything by the Swindon book. For example, slippery bolts are removed with a magnet rather than your fingers to avoid dropping them onto the finely ground bearing surface of a crank journal or into the engine, and threads on the connecting rods are covered with plastic tubes during the process to avoid damaging the crankshaft.

The next stage I try is installing the chain drive to the camshafts. The camshafts open and close valves to let fuel and air in and exhaust gas out. Their design is one of the most crucial aspects of getting maximum power and torque from the engine, and the position in which they are installed relative to the crankshaft is critical. With gauges to set the correct position of the cams and number one piston at the top of its throw (top dead centre), I install the chain, plastic tensioners and gears on the cams using positioning marks for alignment.

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The cams are designed with CAD (computer-aided design) tools and made in-house on CNC (computer numerical control) machines, and their exact profile is a closely guarded secret. Machining interrupts the grain structure of the steel, so they are rough cut then stabilised at 580deg C for five hours before being quenched in oil and finished.

A brief trip to the CMM (co-ordinate measuring machine) room gives an insight into the incredibly precise checking of components. We then head to the engine dynamometer cell, where the engines are calibrated, run in and tested. It takes about an hour to set the engine up on the dyno with cooling and fuel systems. Temperatures are measured in the engine, in the intercooler and in two places on the exhaust. Air conditioning is used to maintain 15deg C at the air intake of all test engines.



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