New ONE of the most important news items for motor racing enthusiasts in New bealand and Australia in recent months has been the announcement of a new racing engine designed specifically with the Tasman formula in mind. The formula will continue as al present until 1968 at least. No drivers will be using the new engine this season, but it is almost certain lo be in wide use next season. If it is successful, as is hoped it may, by next season, have replaced the successful and long-lived Coventry Climax fourcylinder engine almost completely. This Tasman series may he the swan-song of the robust Coventry Climax. Repco late last year announced the most important development yet in its Repeo-Brabham racing programme: complete Repco V8 raeing engines, fully designed by Repeo engineers and produced almost entrely in Repco factories. The first to be produced was a Tasman formula 2.5 litre, which is designed for approximately 250 bhp at 8000 rpm, with useful power through the wide limits of 5500 and 8500 rpin. The substantial power at lower speeds will be of special value on the short circults usual in Tasman formula racing. It is officially designated the Repco-Brabham Type 620, from its project number. It has been designed for installation in chassis designed 10 carry the Coventry Climax four• cylinder. The Type 620 has undergone comprehensive testing and development at the Repeo engine laboratory in Richmond, Victoria, but it is not intended to race it in the present season in the Tasman formula events. SPORTS RACING It will soon appear in sports car racing, in 4.3litre form, as it is readily adaptable to production in any capacity up to this size. By next season, the 2.5-litre version will be available to anyone requiring one, an arrangement which Repco regards as being fairest and - 66 19- Engine May Replace Climax in the best interests of the sport. The 4.3 version is of interest lo sports car racing competitors overseas as well as in Australia, and therefore has the widest potential. Meanwhile, Repen has arranged with Coventry Climax for a supply of castings and other components required to keep Climax engined cars in raceworthy condition throughout the present season. These will be machined locally to Coventry Climax specifications, and will be available to all requiring them. The decision to build the V8 engines was taken in february, 1964, when it seemed obvious that the reserve four-eylinder Climaxes would be certain to dry up well within the lifeline of the Tasman 25litre formula. Also, it was recognised that the designing and bullding of racing engines, from the ground up, was the logical next stage in the Repco-Brabham racing programme from the viewpoints both of research and publicity for the conpany's technical skills and resources. It was only 51 weeks later, March 21, 1965, that the first engine roared on one of the dynamometers in the laboratory at Richmond, an extraordinarily short space nf time between the first pencil mark on the paper and the test runs of a new engine, whatever its typc. The V-8 configurallon was chosen because it was felt that the limits for the development of a fourcylinder engine had been very nearly reached in the Coventry Climax-based 2.5litre, and the only avenue for progress was multiplication of cylinders to provide greater piston area. DESIGNER The design assignment was placed in the hands of Phil Irving, who is internationally known as an engine designer, with the project as a whole under Frank: Hallam, M.S.A.E., chief engineer of the Repco Engine Parts Group of companies, who for many years has been prominent on the technical development side of motor sport in Australia. 38* on a test rig and has pel formed satisfactorily. INTERCHANGEABLE The alloy heads are interchangeable, one with the other, an important practical advantage, since a single spare will provide for either bank. Valve seats are of austenitic cast iron. Valve guides are bronze, with the centre portion exposed to direct water cooling. The head as a whole has been most carefully designed from the cooling aspect. The water is carried along an external alloy manifoid direct from the pump and each combustion chamber has its own independent entry, the water flowing across to four independent exits on the opposite side, the entering flow impinging directly on the exhaust valve guides. Exhaust valve heads and stems It was decided to short- circuit one costly foundry operation by making use of an existing light-alloy crankcase, but even this component had to be greatly modified to suit its new purpose. With this as a basis, the design was worked out for the cylinder head, timing cases, sump, oil-punps and other ilents calling for complex pallern making and specialised magnesium-alloy lechniques. The crankshaft: was machined by Daystall Engineering, leading British specialist in this work, from a billet of EN52 nitriding steel. EXISTING COMPONENTS Naturally, thorough investigations were made of the possibilities for using existing components to simplify production of the engine and keep down costs, but only major existing component which could be utilised was the crankcase. As designed originally this was not considered to be nearly stiff enough for the planned power output; and also it was intended for a pushrod engine, whereas the Repeo engine has overhead camshafts. The stiffness problem was overcome partly by considerable refabication by welding which, in any case, was required in the conver- sion from the original pushrod layout, and also by the use of a 3/1ßths-in steel Stiffening plate bolted at sump flange level to provide complete transverse webhing. It also forms a more substantial atlachment for the front engine bearers. The crankcase and cylinder block provides for wide latitude in engine capacity, from the present 2.5 litre up to 4.3 litres, which should make it adaptable for a really formidable sportsracing car. VALVE GEAR Two dimensional factors basically dictated the cholce of a single camshaft and vertical valves for each bank rather than two shafts and inclined valves. One was the requirement that the engine should be capable of installation in existing Repeo-Brabham frames, in which the distance between the side-members would not accommodate a second camshafl housing. The other frontal area to existing limits with the Climax engine, thus preserving the excellent penetration of the 1965 cars. A futher bonus was consilerable saving cost, an important factor as racing is organised in Australia, with limited financial backing for many drivers. Vertical valves were chosen because they allowed direct cam attack through piston type cam followers. The two valves are set in a central "bathtub" combustion chamber in the bead, with the single plug angled laterally to a near-central position. Compression ratio on the 2.5-Mue engine is 11:1 The camshafts are fve- bearing, carried in light alloy blocks. Each is chain driven through dogs and carries its own vernier adjust- showed no signs of heating when inspected after a 20hours continuous run on the dynamometer at high power output. Relatively little cooling is required by the bores, and their water circulation is adjusted accordingly. Only smah holes connect the water jacketing of the head and the block, minimising risks of gasket failure. The waterpump has a Impeller and two outlets, one for each cylinder bank. Pistons are of the slipper type, each carrying two compression rings and one vil ring. The engine has been designed for fuel injection, the ment to permit precise synchronisation of timing between the two banks, overall timing adjustment being by a third master vernier coupling affecting both shafts or heads without aflecting the timing. The camshafts are dritled through for pressure lubrication, the entry of oil being from the front bearing, which is supplied from a passage drilled through block and head to eliminate pipework. Valve gear has been run up to 10,000 r.p.mn. system under consideration being a new one which is very light in weight and simple. Meanwhile, testing has been going on with Weber carburetters. CRANKSHAFT The 45lb crankshaft 1s of Repeo design, with all throws in a single plane, and this resembles a fourcylinder shaft. It is fully counterbalanced, resulting in extremely smooth operation. Vibration present is at such frequencies as to he harmless and for all 25 practical purposes mech cally negligible. Its effe cannot even be detected vibration of wires when engine is running at evs and can be felt o through the hand The full counterbalanc entailed small wei penaity, but this is m than ofiset by the elimi tion of the need for rougher engine. A fo cylinder fring sequence cach block also makes p sible a more efficient haust system. The accessory drives fr the crankshaft are by t chains, for the water pu: and the camshafts resp lively, and a gear for oil pumps. The water pu chain runs to a jack sha and the camshaft chain triangulated to the shafts and also takes In distributor drive. LUBRICATION Lubrication is at 50 sq. in, from a gear-driv duplex pump, and oll supplled through a full-fl filter. other protecti devices being a gauze scre covering the sump, a lar magnetic plug on the scave ging circuit and a small one on the pressure si between pump and filter. The alloy sump bas longitudinal cast-in galle at the bottom, forming t intake for the scavengi: pump which draws from centre. This gallery has inlet port at each end. a contains a freely slidi shuttle valve. The functi of this component is slide back and forth und the inertia forces imposi by braking and acceleratl so that the pump will dra always from the end of tl sump to which the oll h surged to maximum dept In the unlikely event of fl valve sticking, one at lea of the inlet ports will r main open and the pun can continue to function.