Posted 25 January 2004 - 16:15
The following was researched and written for Profile Publications (GB) in 1973:
"An Engine is Born
The Repco V8 was conceived in February 1964 when the Melbourne management realized that supplies of Climax FPF bits and pieces would probably dry up within the life of the Tasman Formula. Chief Engineer Frank Hallam and Project Engineer Phil Irving were detailed to produce an engine to fit existing Repco Brabham chassis, and their answer was a new V8 using an existing GM Oldsmobile all-aluminium block. -
The obvious way to obtain more power from an unchanged capacity of 2k-litres was to use more cylinders, increasing piston area and crankshaft speed, hence the choice of a V8. It was then expedient to side-step a slow and costly foundry operation by using a proprietary block, and it so happened that General Motors in America had just shelved a suitable unit.
This Oldsmobile F85 had been developed as part of an enormously costly linerless aluminium engine programme for a 3-litre Buick “compact”. The linerless idea didn’t work out so a few units were produced with cast-in ferrous liners, but that made the whole thing too fiddly for mass production. and GM cut their losses and scrapped the whole idea. Repco picked up the pieces, and turned commercial failure into a sporting Champion. Irving found that the basic block could carry 2.5 to 4.4-litre internals, so could double as a Tasman Formula or Group 7 sports-car engine. It would need stiffening. and overhead camshafts would have to replace the standard centre camshaft within the Vee which operated overhead valves by long pushrods. There were two basic parameters to observe; one, that frontal area should be minimised to maintain the existing Repco-Brabhams’ excellent penetration, and, two, that overall width should be limited to fit existing chassis frames.
Irving consequently evolved simple mirror heads for each bank of cylinders, carrying parallel valves in simple wedge-shaped combustion chambers, angled inwards at 10-degrees from the cylinder axis and operated by single overhead camshafts to keep the unit narrow, and to reduce the length of unsupported drive chain to each shaft.
Basic work on the block tilled all unwanted holes and spaces allowed for the original push-rod valve gear, and a ladder-formation stiffener plate in ??-inch thick steel was then screwed to the sump flange to tie the crankcase crosswise. New main bearing caps were retained by long bolts which passed deep into the crankcase. and the existing 3.5-inch bores were reamed and fined with 10-thou thick Repco cast liners. With a bore and stroke of 85 mm x 55 mm the capacity of 2.5-litres was achieved. Laystall in England machined new crankshafts. which ran in five Repco bearings, and another short-cut was taken when lightened and balanced Daimler V8 con rods were found suitable.
Repco pistons were cast in aluminium silicon alloy, with shallow valve clearance indents in their crowns, and Irving’s new mirror heads were identical in every dimension to ease the spares situation; it was all good basic practical design.
The engine’s internals were all-new, and two beautiful magnesium castings completed the conversion; a Y-shaped cover for the camshaft drive chains and a new 3½-inch-deep ribbed sump which helped to stiffen the crankcase even more to accommodate its designed power increase. Adaptors were available to suit either Weber carburettors or Lucas fuel injection, and Repco even made their own specialized oil and water pumps to suit. Basic dimensions showed a length of 25½-inches (excluding the Climax FWB fly-wheel), width across the heads of 21 -inches, and height (excluding induction equipment) of 23-inches.
The prototype 2.5-litre engine coughed its way into the world on Repco’s Richmond, Victoria, test bed on March 21, 1965. only 51 weeks after Irving and Hallam first put pen to paper. It was at about this time that Brabham and Repco began talking about producing an intermediate 3-litre variant for Formula One, and Phil Irving spent much of the summer in England, working closely with Jack himself on detail design of the new variant. They reverted to the standard 3.5-inch (88.9 mm) bore, and adopted a piston stroke of 60.3 mm, to give a swept volume of 2,994cc. With Lucas fuel injection this new version gave 285 bhp at 8.000 rpm in early tests. and all Brabham had to do now was fit it into a chassis to have his 1966 Formula One car.
However, Ron Tauranac felt that M RD’s lack of direct involvement with Formula One was most unsatisfactory. and it had then lasted for three whole seasons. Before work began on the new car, a new agreement was evolved with BRO, giving MRD their direct involvement and Tauranac the incentive which had been so lacking in the 1½-litre days.
This arrangement was finalized as late as November, 1965, and a crash programme began to build up a new Repco-engined car for the first official race to the new Formula. the non-Championship South African GP at East London, on January 2.
The Repco V8 1966—1968
In 1966. the Oldsmobile F85-based RepcoBrabham engine became known as the type 620. and engine numbers were all prefixed ‘RB-620’. This was a two-part classification, the ‘600’ applying to the block and the ‘20’ to the cylinder heads. Engine numbering began at ‘RB 620—E1’.
During the year the engine proved very reliable and produced sufficient usable power to make the light and good-handling Brabham chassis extremely competitive. At Monza for the Italian GP the BRO transporter disgorged three cars and an engine, newly crated from Melbourne, with “Monza 350 hp” stenciled on the crate. In fact engine ‘E7’ produced a peak of 298bhp on Repco’s test-bed, and after attention to the porting and a raise in compression ratio John Judd (BRO’s ex-Climax engineer) saw 311bhp at 7.250 rpm on the Climax dynamometer. There was more to come but at this point a piston burned out.
New developments were in hand for 1967, and during the following months a whole family of Repco V8 bits and pieces were developed, the blocks taking hundred-series numbers and the heads ten-series.
The basic deficiencies of the Oldsmobile production block and the complex operations necessary to bring it up to racing specification made the production of an all-new block a near necessity, and the 1966 World Championship success gave Repco the impetus to press on with its production. The 20-series cross-flow heads had also provided a low-level exhaust system which gave the chassis designer headaches weaving the pipes through his suspension system. So new heads were developed with their exhausts exiting within the Vee to clean-up the installation.
Repco engine developments were at this time being carried out by Repco-Brabham Engines Pty Ltd at Maidstone, outside Melbourne, where a four-man design team were working under general manager Frank Hallam, and with Phil Irving’s strong influence their guiding light. The new team was headed by Norm Wilson, assisted by John Judd (down from England), Lindsay Hooper and Brian Heard.
The crankcase was redesigned to increase rigidity, and was cast in aluminium alloy. A change was made to wet liners and cross-bolted main bearing caps, and there was also a system of main bearing studs which distributed stress right through the new crankcase. These studs screwed into the bottom of the case, and continued right through it with reduced diameter, relieving stress concentrations through the top of the new block where they were provided with nuts, tightened down after the main bearing nuts had been tightened.
The new cylinder heads retained parallel valves, but they were now in-line with the cylinder axis—instead of at 10-degrees to it— and were flush with the head face. Camshaft centres were naturally changed to suit, and the original 20-series wedge-shaped combustion chambers were replaced by a “bowl-in-piston” arrangement. The all-new block took the ‘700’ type number, and it represented a weight-saving of 30 lbs over the original Oldsmobile-based component. The new centre-exhaust heads were known as the type ‘40’... so what had happened to the type ‘30’?
This was indeed the second design completed, but it retained the original cross-flow characteristics with outside exhausts, and mated that system to the new in-line valve/bowl-in-piston features. At the time it was felt that with parallel valves the gas had to make a pretty sharp turn as it left the cylinder, and it was immaterial to the gas which way it turned. The fallacy of this argument was proved when some serious tests were run with the 30-series heads, but when exhaust installation became of paramount importance the 30-series was held over, and the centre-exhaust type ‘40’ heads took their place in the 1967 type 740 engines.., and another World Championship came Repco’s way.
At the end of 1967 the Repco-Brabham range of V8 engines included the old Formula One 3-litre and sports-racing 4.4-litre 620s, and the new 740s in both 3-litre and Tasman 2.5-litre trim. Original 2.5 620s were still available, and new 4.2 and 2.8-litre Indianapolis engines were on the stocks (the latter with AiResearch turbocharging).
Highest output achieved from the Fl 740s was only 330 bhp, but all Repco’s horses seemed to be hard workers compared to the 408 claimed for the new Cosworth-Ford V8 and the 417 or so of the Eagle-Weslake V12. Nonetheless, something fairly drastic had to be done if the Repco- Brabhams were to be competitive in 1968.
There were two avenues of approach. One was for a short-stroke magnesium block engine, and the other was for a daring new cylinder head design, using a radial valve disposition. As it turned out a combination of the new and existing ideas was chosen, using aluminium short blocks with twin-overhead camshaft, four-valve per cylinder heads; without the complex radial layout, or short stroke.
Developments of the held-over 30-series heads had proved there was a power advantage to be achieved from cross-flow gas paths, and the radial-layout type ‘50’ heads aimed to exploit this advantage to the full. They were intended to use twin overhead camshafts per bank, each one driving inlet and exhaust valves alternately. The valves resided side-by-side in each half of a conventional pent-roof combustion chamber, exhausts and inlets being diametrically opposed across the chamber. This layout allowed very simple valve operation. compared to BMW’s F2 Apfelbeck heads in which a radial valve layout appeared in hemispherical combustion chambers; the BMW valve stems protruded in all directions, like the horns on a sea-mine I
On the Repco test heads exhaust stubs appeared within the Vee as a bunch of eight small-bore pipes, while four more appeared below the heads outside the Vee on either side. Eight induction trumpets fought for space within the Vee, and four more appeared on each side. One test engine was built-up using these heads and results were “most encouraging” but it was all a blind alley once again due to installation problems.
So the type ‘50’ heads were shelved, and Repco (who had a lot of originality inside them, fighting to get out) adopted a more conventional ‘60’-series design, using twin ohc and conventional four-valve per cylinder layout, with cross-flow gas-paths, neatly tucked-away outside exhausts and Lucas injection gear uncluttered within the Vee. These heads were mounted on the new 800-series block, which was fully 1¼-inches shallower in the crankshaft centre-line to head interface dimension than its forerunners. It was considerably lighter, despite the use of a nitrided gear train to drive the new multiple camshafts, and was suitable only for 2.5 and 3-litre capacities. Part of this weight-saving came from the use of new crankshafts with fewer balance weights, and the original 800-series block to be raced was cast in magnesium. It made its debut in the 1968 Tasman series, but in Formula One it eventually ran out of water and pulled out of line. It survives in John Judd’s hands today in Rugby.
One short-stroke test engine was built-up using a 2½-litre crankshaft, bigger bore and a 5-litre sports-car head (a 700-series development of the 600-series 4.4-litre engine) carrying bigger valves to take full advantage of the extra bore. It showed no power advantage, and the short-block 800-series engines appeared in 3-litre form with shorter con-rods, using 5.1-inch centres instead of the original F85/620/740-type 6.3-inch-centre components. Time spent on these developments cost the quad-cam 60-series dear, and Brabham and Tauranac could have been forgiven for buying Cosworth-Ford engines as the 1968 season progressed from problem to problem. The Mexican GP saw Repco’s last Fl appearance in a works car, for the 12.000 miles between Melbourne and Guildford proved an insuperable obstacle to race development.
Jack Brabham drove a new Tasman car fitted with an 830 engine in the Tasman Championship early in 1969, and since then Repco have rested on their hard-won laurels, and have concentrated on service of their Tasman and Indianapolis V8s, and production of a successful Holden-based Formula 5000 engine." (...AS OF 1973)
Blackie still bitterly regrets not having stayed with the 740 16-valve engine for 1968 instead of the 860 32-valve. However, the 4-valve per cylinder heads worked well on the big 4.2-litre 4-cam V8 Repco Indy engine, which proved crucially lower-revving, keeping below the resonant range which was destroying the cam followers in the 3-litre Formula 1 860s.
DCN
