New Engine May Replace Climax 2.5

Press, Volume CV, Issue 30962, 19 January 1966, Page 15

New Engine May Replace Climax 2.5

QNE of the most important news items for motor racing enthusiasts in New Zealand 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 at present until 1968 at least.

No drivers will be using the new engine this season, but it is almost certain to 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 be the swan-song of the robust Coventry Climax. Repco late last year announced the most important development yet in its Repco-Brabham racing programme: complete Repco V 8 racing engines, fully designed by Repco engineers and produced almost entirely 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 rpm. The substantial power at lower speeds will be of special value on the short circuits 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 to carry the Coventry Climax fourcylinder. The Type 620 has undergone comprehensive testing and development at the Repco 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 43litre 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

in the best interests of the sport.

The 4.3 version is of interest to sports car racing competitors overseas as well as in Australia, and therefore has the widest potential. Meanwhile, Repco 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 V 8 engines was taken in February, 1964, when it seemed obvious that the reserve of four-cylinder Climaxes would be certain to dry up well within the lifetime of the Tasman 2.5litre formula. Also, it was recognised that the designing and building 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 company’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 of time between the first pencil mark on the paper and the test runs of a new engine, whatever its type. The V-8 configuration 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 multiplica-

tion 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.

It was decided to shortcircuit 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-pumps and other items calling for complex pattern making and specialised magnesium-alloy techniques. The crankshaft was machined by Laystall Engineering, a leading British specialist in this work, from a billet of ENS2 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 Repco engine has overhead camshafts.

The stiffness problem was overcome partly by considerable refabication by welding which, in any case,

was required in the conversion from the original pushrod layout, and also by the use of a 3/16ths-in steel stiffening plate bolted at sump flange level to provide complete transverse webbing. It also forms a more substantial attachment 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 choice 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 Repco-Brabham frames, in which the distance between the side-members would not accommodate a second camshaft housing. The other frontal area to existing limits with the Climax engine, thus preserving the excellent penetration of the 1965 cars.

A further bonus was considerable 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 head, with the single plug angled laterally to a near-central position. Compression ratio on the 2.5-litre engine is 11:1. The camshafts are fivebearing, carried in light alloy blocks. Each is chain driven through dogs and carries its own vernier adjusts

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 affecting the timing. The camshafts are drilled 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.m.

on a test rig and has performed 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 manifold 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 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 small 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 oil ring. The engine has been designed for fuel injection, the

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 451 b crankshaft is of Repco 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 be harmless and for all

practical purposes mechanically negligible. Its effects cannot even be detected as vibration of wires when the engine is running at full revs and can be felt onlythrough the hand. The full counterbalancing entailed a small weight penalty, but this is more than offset by the elimination of the need for a rougher engine. A fourcylinder firing sequence in each block also makes possible a more efficient exhaust system. The accessory drives from the crankshaft are by two chains, for the water pump and the camshafts respectively, and a gear for the oil pumps. The water pump chain runs to a jack shaft, and the camshaft chain is

triangulated to the two shafts and also takes in the distributor drive. LUBRICATION Lubrication is at 501bs sq. in, from a gear-driven duplex pump, and oil is supplied through a full-flow filter, other protective devices being a gauze screen covering the sump, a large magnetic plug on the scavenging circuit and a smaller one on the pressure side between pump and filter. The alloy sump has a longitudinal cast-in gallery at the bottom, forming the intake for the scavenging pump which draws from its centre. This gallery has an inlet port at each end, and contains a freely sliding shuttle valve. The function of this component is to slide back and forth under the inertia forces imposed by braking and acceleration so that the pump will draw always from the end of the sump to which the oil has surged to maximum depth. In the unlikely event of the valve sticking, one at least of the inlet ports will remain open and the pump can continue to function.