"When, on January 3, 1984, Mario Illien set out to design an IndyCar engine for his new company [Ilmor Engineering], he was the first person to do so from a clean sheet of paper since Leo Goossen conceived the supercharged 3.0 litre Novi V8, which made its debut in 1941.”
EDL’s Brabham-Honda AV engine first ran on track at Laguna Seca in December 1985. EDL has evidence that the design work began on August 12, 1983, and that the AV had its first dyno test on March 2, 1985 (whereas the 265A had its first dyno test on May 16, 1985)
In response to that statement in RET 146’s profile of the Init Racing Ilmor Chevrolet 265A, historian David Hebb commented, “The Drake DT-160 V8 and the Callaway HH V8 precede the 265A. The first was a John Drake and Hans Hermann design, the second by Hans Hermann alone.”
Then Karl Ludvigsen drew our attention to Art Spark’s earlier (but post-Goossen) clean-sheet flat-six, which like the Callaway failed to reach the racetrack. And so it went on; the list was soon threatening to mushroom, especially as we didn’t have a definition of a ‘clean sheet of paper’ design.
Let’s be pragmatic: logically it is not one that adopts the block and/ or head architecture of a production engine. Logically it is not an evolution or adaptation of an existing Indy engine. Nor is it an adaptation of one developed for another form of racing.
Even with those criteria, our original statement was incorrect: Drake, Hermann and Sparks began clean-sheet designs before Illien – doubtless others too, given the time span of almost 50 years and the vagueness of simply ‘starting to design from a clean sheet of paper’.
So again, let’s be pragmatic. For practical reasons let’s confine our consideration to engines that powered a car that competed in the Indianapolis 500-mile race. Only those are listed in the accompanying Indianapolis Race Engine Directory 940- 89. We chose 1989 so as not to overlook any engine, the design of which might have begun before January 3, 1984.
Our directory ignores non-qualifiers. It identifies the provenance of each Indy 500 race newcomer during the half-century it spans. It proves that none of the post-Novi engines identified had a clear-cut clean-sheet provenance until the arrival of the 265A.
‘Semi-stock’ indicates a production-derived block. The 1963 Ford V8 used modified production patterns for its aluminium block; the same block was used for the 1964 DOHC evolution, so neither qualifies as clean sheet. The 1948 Fageol I6 is not definitively documented anywhere as to whether it used the production iron block and head or the aluminium versions the factory developed for hydroplane racing. Either way it fails our clean-sheet criteria.
However, the status of the 1968 Repco Brabham is unclear, and it is discussed in the following interview with John Judd Snr. Having read that, readers must make up their own mind as to whether the Repco Brabham qualifies by our reasonable definition as clean sheet.
John Judd Snr’s 1987 Indy 500- debuting Judd AV (aka Brabham-Honda) most certainly was clean sheet, as was the Ilmor 265A and the 1988-arriving Porsche Typ 2780. Although it was the first of those 2.65 litre V8 turbos to take starter’s orders at Indy, in 1986, does that mean we can we say with confidence that the Ilmor 265A was the first upon which design work started?
The author interviewed Hans Mezger at length on the subject of the Typ 2780 back in 1989. He reported that he started design work in 1986. However, John Judd Snr has confirmed that he began work at Engine Developments Ltd on his clean-sheet IndyCar engine, the Honda-supported AV, on August 12, 1983.
So if we take the pragmatic approach whereby our statement is understood to imply clean-sheet engines that contested the Indy 500 race then it is unfair to John Judd Snr (and arguably to his 1960s Repco Brabham colleagues as well). To be fair to Mario Illien though, he was the first person in the half-century under consideration to design an engine from a clean sheet that would win the Indy 500.
The 1968 Repco Brabham Indy V8
The 1968 Repco Brabham was not an evolution or adaptation of an existing Indy engine. Nor, arguably, can it be discounted as an engine developed for another form of racing or an adaptation of one. It was one of a family using the same platform designed concurrently for multiple applications: Tasman, Formula One and Group Seven sports racers, as well as Indy Cars.
Moreover, resources were allocated such that there were fundamental redesigns from 1966 to ’67 and from ’67 to ’68. By mid-1960s standards that was a formidable commitment, one that has to be seen in the context of the Formula One version having claimed the World Championship in 1966 as well as ’67.
Another consideration here is that this Repco Brabham Indy engine had a block related to that of the Oldsmobile F-85 production V8. Does that mean we should deny it clean-sheet status? To properly investigate we spoke to John Judd Snr, the last surviving member of the team that designed it.
The Oldsmobile connection
Judd started his career in 1960 as an apprentice design draughtsman at Coventry Climax. He recalls that in the early ’60s, “Jack [Brabham] brought in an aluminium V8 Oldsmobile F-85 block for us to have a look at. It was a lovely casting, better than we could do at the time. I remember everyone being most impressed with the casting quality compared to the horrors of sand casting available to us at the time.
“Jack then sold it to Repco as the basis of a V8 that could beat the Climax four-cylinders in the [Australia/New Zealand] Tasman series [for naturally aspirated 2.5 litre engines].”
Once that was agreed, the work was undertaken at Repco in Melbourne under the direction of chief engineer Frank Hallam. The design work was by project engineer Philip ‘Phil’ Edward Irving, well-known for Norton, Velocette and Vincent motorcycle engines (RET 135, November/ December 2021). Irving was a good friend of fellow Australian Brabham.
The F-85 90o V8 was Oldsmobile’s version of the all-aluminium pushrod Buick 215 (the F-85 differed from the 215 by having a six rather than five-bolt head fixing). Having a 4.24 in bore spacing and as stock displacing 215.15 cu in (3.53 litres), these early ’60s linerless engines were the lightest production V8s in the world. But GM did not find success on the street with them, and Repco was able to buy a batch of F-85 blocks at an attractive price.
John Judd Snr was a member of the Brabham Racing Organisation from 1966 and was sent to the Brabham Repco engine facility in Australia for spells in 1966 and 1967, during which he played a key role in the design of the block and heads of the 1968 Indy engine. Here he is back in the UK in 1966 with that year’s Formula One version of the Repco V8. Behind the 1966 Formula One car are (from left to right) mechanics Bob Ilich, Roy Billington (chief mechanic), Hughie Absalom, John Muller and Cary Taylor, then drivers Denny Hulme and Jack Brabham, car designer Ron Tauranac, Judd himself and Brabham’s manager Phil Kerr
To produce a 2.5 litre Tasman engine, Irving designed a suitable upgrade to the F-85 block and bespoke cylinder heads to fit it. Those had two valves per cylinder, both inclined at 10o from vertical to form a wedge-shaped combustion chamber. With the pushrod system disabled, each head had a chain-driven single camshaft directly operating its valves.
The chain drive ran in its own self-contained front-end housing that mounted the necessary spindles. There was an Oldham coupling to each camshaft – “I think that was motorcycle-influenced,” remarks Judd. “Because Phil was experienced in the motorcycle industry he did use a few parts from road bikes and cars. Initially the Repco V8 used Daimler con rods, Jaguar tappets, BSA valve springs and some Triumph bits and pieces!”
An aluminium sheet was placed over the exposed cam follower bores and the opening above the redundant camshaft. This was held in and sealed with a large amount of Araldite. The bottom end was further stiffened with a ladder-form 3/16 in-thick steel plate, below which was fitted a bespoke ribbed magnesium sump.
New main bearing caps with revised attachment retained a racing-specification cranktrain. The flat-plane crankshaft was machined from a billet of EN40 nitriding steel by Laystall in the UK. Repco produced its own light alloy three-ring, slipper-type pistons, which reciprocated in Repco dry-cast iron liners. Repco even made its own oil and water pumps.
The bore was 85 mm, the stroke 55 mm for 2497 cc. The engine was optionally carburettor-equipped or mechanically injected using the Lucas system. The first example was run on the dyno at Repco in Australia in March 1965. The summer of ’65 then found Irving detailing a mechanically injected version for Formula One from 1966. This married the stock Oldsmobile 3.5 in (88.9 mm) bore to a stroke of 60.3 mm for 2994 cc.
Judd joined the Brabham Racing Organisation (BRO) in the UK in March 1966, a couple of months after the new Repco V8 had powered Jack Brabham to pole and fastest lap in its first race, the non-championship South African Grand Prix. His job initially was to go to Repco Brabham Engines in Australia to assist in design of the 1967 V8, a multi-purpose platform for Formula One, Tasman and (at 4.4 litres) Group Seven sportscar racing.
Judd spent four months there, during which Irving left and was replaced by Norman ‘Norm’ Wilson; Lindsay Hooper and Brian Heard were other members of the design team overseen by Hallam. Hallam instructed Judd to draw a two valve per cylinder Heron-type head with upright valves, which he duly did.
The 1966 World Championship-winning Formula One engine in its initial guise was known as the 620, the 600 indicating the Irving-modified F-85 block and 20 indicating Irving’s two valve per cylinder wedge head. The Heron head was then the 30 series. In fact there were two versions, the second having the exhausts exiting within the vee, and this 40-series Heron head was specified for 1967.
The Repco-Brabham 760 Indy engine was one of a family of new four valve per cylinder V8s designed for Formula One and Group Seven sportscar racing, as well as IndyCar in 1968. At Indianapolis it powered the Brabham BT25, an example of which has been superbly preserved by the Rofgo Collection
For 1967, the chain timing drive remained essentially the same, aside from adaptation for the repositioning of the camshafts dictated by the upright valves. Meanwhile, Wilson had designed a new sump that set the pumps at the front, below the still self-contained timing chest. There was also a 700-series block, which had been first used towards the end of the 1966 season.
The 700 block
Judd explains, “Repco was fed up with constant references to the modified Oldsmobile block. This came to the notice of Norm and myself, and after a discussion we agreed that we should be able to design a new Repco block in the course of a weekend if we were prepared to put in the hours.
“This 700-series block was indeed designed and detailed over the course of the weekend. It raced successfully later in ’66 [as the 720] and became the basis for the 1967 single-cam engines [740] and 1968 twin-cam four-valve engines, including the 4.2 Indy version.”
Another shot of the 760 Indy engine in the Rofgo Collection’s Brabham BT25 chassis BT25/2 of 1968. This UK-based collection assembled by Roald Goethe hosts a number of historic Gulf-sponsored racecars, which are taken to various historic racing events
To allow cylinder heads to be interchangeable, the 700 block retained the 4.24 in bore centre spacing of the 600. It also retained the deep (below crankshaft axis) skirt of the F-85. In fact the deck height was F-85, as was the sump joint position, while the front and rear faces were also in the same positions. The Repco 700 block was a straight replacement for the Oldsmobile-based 600.
Jochen Rindt qualified the Repco-Brabham 760 V8-powered Brabham BT25 in 16th for the 1968 Indianapolis 500 but was an early retirement (Courtesy of IMS Photo)
“The deep skirt allowed cross-bolts into the main bearing caps,” notes Judd. “In the production engine the F-85 used cast iron caps, and those weren’t cross-bolted. Our cross-bolted 700 main caps were steel.” The vertical main bearing studs protruded up into the valley, from where they were tensioned. “That was probably my idea,” reflects Judd. “Basically, you screwed in the stud conventionally and it was long enough to extend up into the centre vee. You torqued it up and then put a bolt on top. That took some of the tensile and bending loads out of the casting and the main bearing caps.”
This through-bolting plus the cross-bolting eliminated the need for an aluminium stiffener plate to be sandwiched between the block and the sump. It all made the bottom end very rigid. The 700 block was closed deck with wet cast iron liners. Each liner was secured by a flange at the top and was free to expand below. This overcame bore distortion problems encountered with the dry sleeves in the 600 block.
Cooper rings were seated into the top of each wet liner, and the head gasket was retained only to seal the water and oil passages at the block-to-head interface. Judd notes, “The shape of those passages had been designed for a conventional gasket, and they would have been too difficult to O-ring seal in those pre-CNC days.”
In respect of the coolant provision, Judd remarks, “That was the same in principle, because the water inlets, outlets and transfer points to the head were the same, so they could use the same heads on both the 600 and the 700. We also ran the same water pump, as I recollect. However, the water system detail would have been different, because putting in wet liners changes how the water passages are.
“The 700 block was mostly of conventional 150 thou wall thickness. It wasn’t a completely different design in terms of the walls and the structure compared to the Oldsmobile, although the Oldsmobile having the cylinder bores cast in was a different animal.”
Some 30 lb lighter as well as stiffer than the reinforced 600 block, the 700 was sand cast in LM8 aluminium alloy in Australia by the Commonwealth Aircraft Corporation. Was that casting getting up to F-85 quality?
Jack Brabham himself qualified for the 1969 Indy 500 but was an early retirement. Brabham teammate Peter Revson (Courtesy of IMS Photo)
“Probably not in terms of getting shrinkage and the boss positions right,” Judd says. “The thing we at Climax couldn’t believe about the F-85 block when we first saw it was how they got all the holes right in the middle of the bosses. It was routine in those days for a hole to be half out of a boss because of shrinkage or the core joints not being right!
“But the Repco block was a reasonable job. It wasn’t a complicated casting either – we kept it pretty simple.”
The move to 32 valves
Thus was the 1967 Formula One engine, which powered the BRO to its second World Championship title, the 740. New for 1968 was a four valve per cylinder head using double overhead camshafts. Judd went to Australia for six months from March 1967 to assist in the design of this new multi-purpose V8.
Judd recalls that initially he was instructed by Hallam to design a pent-roof chamber on Apfelbeck principles, having an exhaust valve and an intake valve on each side. Those unconventional pairings were parallel so that the same camshaft, having alternate intake and exhaust cams, could operate both valves, each having its partner diametrically opposed across the chamber.
Clearly consequent was a huge complication in terms of the porting. As Judd puts it, “This was all just for a combustion theory. I was no expert in combustion theory but I couldn’t see this was going to be practical. And I guess history has proved me right!”
Happily, having listened to Judd, Brabham convinced Repco to drop this 50-series head. “Instead we did a 60-series head with a conventional four-valve layout, which Norm and I knocked out pretty quickly,” Judd recalls. “It would have had the same included valve angle. Something in the region of 30-40o – probably similar to a DFV, which is 32o.”
Owing to the use of twin overhead camshafts, there was no longer room for a centre exhaust. This type 60 head was destined for both Formula One and Indy Car racing in 1968. Another development for 1968 was an 800-series block having 1.25 in lower deck height. This was for Formula One only, the Indy engine retaining the standard-height 700 block in view of a longer stroke.
The Indy engine
The Indy bore was the established 88.9 mm, while the stroke rose from the 60.3 mm of the Formula One engine to 84.5 mm, for 4196 cc. At the time, 4.2 litres was the maximum permitted at the Speedway for unblown units.
All of the four valve Repco engines were gear-driven, again using an independent gear case, “because there was nowhere on the block to mount gear spindles”, Judd explains. The Oldham couplings were now gone – “this case had openings to allow the camshafts to protrude in so that the gear on the end could mesh with the timing drive”.
The pattern of the Formula One and Indy gear drives was the same, obviously tailored to the respective block height. Both used the 60-series head with the same valve sizes and the same porting, albeit with different cam profiles as appropriate to the application. Overall, the Formula One and Indy valve and crank trains were, “essentially identical except for whatever adjustment we made for the stroke and the deck height”, Judd recalls.
He adds that Indy engine design work “was done in parallel with Formula One. All along, it was designed to be Indy and Formula One on the same platform, although the ’68 Formula One engine ended up with the shorter 800-series block. However, I think the Indy design was chronologically behind the Formula One design.
“Some of the Indy engine work continued after I returned to the UK; they designed it with a twin metering unit drive, as Lucas couldn’t supply a single metering unit to deal with the flow of methanol fuel. That all came out after I’d come back to the UK, but I felt it was going to be a complete disaster, because there were going to be 16 injectors, 16 pipes, two fuel cams and all the linkages – it was a Shop of Horrors!
“Jack was concerned about the coordination between the two [purely mechanical] metering units, and so was I. To get around that we basically invented a new variation of metering unit for Lucas. “I took an existing unit to bits and studied it. A four-cylinder unit had a single shuttle in the centre, whereas an eight-cylinder unit had two shuttles that weren’t in the centre but were offset so they were in the same row. I figured out that you could put two more in as well.
“Lucas said it wasn’t possible so we got our machine shop to mock up a metering unit rotor in steel. It wasn’t functional since it didn’t have the accuracy required, but it showed how you could do it with a single four-shuttle metering unit. Lucas were good enough to make that, and it was on the engine from the beginning of testing.”
The Indy engine used a Bosch ignition system as deployed in Formula One. All the 760 Indy engine build, development and preparation was done out of Repco in Australia. The engine arrived at the Speedway in May 1968, when Jochen Rindt used it to power his Brabham BT25 to 16th on the grid. It was seen again in 1969 when it powered Peter Revson to fifth position.
Was this Indy race engine a clean-sheet design? Judd remarks, “You could take the view that the Oldsmobile beginnings were submerged by the amount of reengineering and evolution over the following years. Or equally you could think the Repco V8s were forever production-based!”
Indianapolis Race Engine Directory 1940-89
WARNING: this is a listing of engines that participated for the first time in the 46 Indianapolis 500 races run 1940-89 (there were no races 1942-45). Engines that participated prior to 1940 are not listed here and nor are those that failed to power a 500-mile starter.
A good number of 1930s engines continued to participate in the 1940s. For 1938, Indianapolis had adopted international Grand Prix rules, which dictated 274 cu in/4.5 litres naturally aspirated and 183 cu in/ 3.0 litres blown. Maserati and Alfa Romeo S8 supercharged Grand Prix cars came strongly into the mix, and the Maserati 8CTF (predecessor of the 8CL) won in 1939 and 1940.
Miller S8s won the most in the 1930s. The last new Miller engine was a blown I6 first raced in 1939. This and blown S8s kept Miller represented through to 1948. The 16-cylinder Sampson had a pair of unblown Miller S8s geared together within a common crankcase. This 4.5 litre contender raced from 1939 through to 1946.
The 1946 win was powered by the Sparks Thorne supercharged I6. Designed by Art Sparks and Leo Goossen, and built by Thorne Engineering for 1938, it was known as the Little Six and was last seen in 1949.
Other 1930s engines seen in the 1940s included Frank Brisko’s blown Brisco I6 and Joe Lencki’s unblown Lencki I6. The latter had been designed by Goossen and built by Offenhauser, as had Leon Duray’s Millerbased blown Duray I4. Also penned by Goossen was a blown Bowes Winfield S8 that arrived in 1938.
The 1940s saw the Miller-derived Offy I4 in the ascendency. Designed by Goossen, it had arrived in 1935, when it took the first of what would be 27 Indy 500 wins. During the 1940s it was for the most part naturally aspirated at 255-274 cu in (according to favoured bore and stroke).
Lou Moore’s Avgas-fuelled Offy wins of 1947-49 are rumoured to have been using an eight-valve head with hemispherical combustion chambers for enhanced fuel efficiency. We have found no hard evidence for that, so it is not listed here as an Offy evolution.
The 38 confirmed race debutants are listed in chronological order. Where there was more than one in any given year, ordering is by starting position. Each entry indicates naturally aspirated (n/a), supercharged (s/c) or turbo-supercharged (t/c). Also the year(s) it qualified and the engine’s provenance. The term ‘monobloc’ here means combined head and block.
Novi (Winfield in 1941)
90o V8 s/c
181 cu in (3.0 litres)
16-valve DOHC
1941/46-49/51-53/56-58
Clean-sheet design
Designed by Leo Goossen and Bud Winfield, and built by Fred Offenhauser. Iron monobloc banks on aluminium and bronze barrel-type three-bearing crankcase. Rear gear timing drive; front gear and torsion shaft drive at 5.35x engine speed for triple carburettor-fed 10 in centrifugal supercharger.
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2 x Offy Midget
2 x I4 s/c
Each 90 cu in (1.5 litres)
Each eight-valve DOHC
1946
New Offy application
Two destroked 97 cu in (iron monobloc/aluminium crankcase) Midget engines. Roots-blown (carburettor-fed). Positioned one at each end; each feeding a Miller front drive unit. Connected only by a coupled throttle linkage. Fageol Twin Coach’s Experimental Division conjured this 4WD car.
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Maserati Tipo 8CL
I8 s/c
183 cu in (3.0 litres)
32-valve DOHC
1946/49
Derived from Voiturette
Factory project for top-level international racing. Fashioned from the 1.5 litre supercharged 4CL I4; two of its iron monoblocs in tandem on a combined light alloy crankcase. Twin Roots superchargers, one for each bank, each having a dedicated carburettor.
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Maserati 4CL
I4 s/c
92 cu in (1.5 litres)
16-valve DOHC
1946
Voiturette engine
Designed by Ernesto Maserati as a new I4 for the (1.5 litre supercharged) international Voiturette class of 1939. Iron monobloc on light alloy crankcase. Front-mounted, carburettor-fed Roots supercharger; individual pipe for each exhaust port.
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Granatelli Mercury
90o V8 n/a
274 cu in (4.5 litres)
16-valve flathead
1946-47
Stock block
Developed by the Granatelli brothers this was a stock Mercury block – a version of the iron three-bearing flathead Ford – fitted with Grancor (Granatelli Corporation) finned aluminium cylinder heads. Bored and stroked to allowed displacement (256 cu in in 1947). Twin carburettor-equipped.
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Mercedes-Benz M163
60o V12 s/c
183 cu in (3.0 litres)
48-valve DOHC
1947-48
Grand Prix engine
Powered a factory Grand Prix contender before the war; one example of this complex W154 racecar at Indy is now privately owned. Aluminium crankcase carrying monoblocs made as combination of steel forging and steel fabrication. Carburettor-fed, two-stage Roots supercharged.
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Fageol
I6 n/a
275 cu in (4.5 litres)
12-valve SOHC
1948
Semi-stock/stock?
Factory-derived from 4.25 in bore 404 cu in production engine with 3.225 in stroke for legal 274.5 cu in. Three-carburettor manifold; exhaust the other side and in line valves upright. High-octane gasoline at 14:1. Unknown if head and seven bearing block stock iron or aluminium versions developed for hydroplane racing. Ed Winfield involved. Either Ed or Bud Winfield then designed the twin exhaust 18-valve head with which the car failed to qualify in 1949.
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Blown Offy
I4 s/c
177 cu in (2.9 litres)
16-valve DOHC
1950-52+
Evolution of the Offy
Developed by (current Offy owner) Mayer-Drake based on 220 cu in Sprint Car version (iron monobloc on aluminium barrel crankcase). Goossen-designed gear-type drive for centrifugal blower with cushioning system. Finned aluminium charge cooler. Mechanically injected from 1951. (Others, most notably Herb Porter, continued to develop beyond 1952 without significant success.)
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Cummins-Roots
I6 s/c
403 cu in (6.6 litres)
24-valve DOHC
1950
Semi-stock
Factory development of the production JBS-600 truck diesel, but here all aluminium with four valves per cylinder. Roots supercharger. Early form of Cummins Pressure- Time common rail injection using engine-driven pump and cam lobe injector actuation. Twin injectors per cylinder.
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Cummins-Turbo
I6 t/c
403 cu in (6.6 litres)
24-valve DOHC
1952
Semi-stock
Further development of JBS- 600 now with a magnesium crankcase. First-ever turbo car at Indy; exploited laydown engine installation.
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Ferrari 375
60o V12 n/a
275 cu in (4.5 litres)
24-valve SOHC
1952
Grand Prix engine
Aurelio Lampredi-designed all-aluminium factory Grand Prix engine fed by three downdraught carburettors.
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Low Tower Offy
I4 n/a
252 cu in (4.1 litres)
16-valve DOHC
1957-66
Evolution of the Offy
Rules forced Offy runners to reduce maximum displacement from 270 cu in to 256 cu in for 1957. Most initially reduced the bore, whereas AJ Watson went for shorter-stroke crankshaft. Used 220 Sprint engine rods and its lower gear tower on a shortened block. Everyone followed.
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Coventry-Climax FPF
I4 n/a
168 cu in (2.75 litres)
Eight-valve DOHC
1961
Grand Prix engine
The all-aluminium Climax had a gear timing drive and twin carburettor induction. This was a 2.5 litre Formula One I4 bored and stroked by the factory to 2.75 litres.
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Thompson Buick
90o V8 n/a
255 cu in (4.2 litres)
16-valve pushrod
1962
Stock block
Developed by Mickey Thompson around the 1961-63 all-aluminium pushrod Buick215, then the world’s lightest production V8. Had a 4.24 in bore spacing and as stock displaced 215.15 cu in. Hilborn cross-ram injection system for qualifying and a stack-style system for the race.
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Novi/Granatelli
90o V8 s/c
167 cu in (2.7 litres)
16-valve DOHC
1963-65
Evolution of the Novi
In 1961, Lew Welch sold the entire Novi project to Andy Granatelli. Assisted by brothers Vince and Joe, he developed it with revised camshafts and porting and new cam followers. Also, as owner of centrifugal supercharger specialist Paxton Products, he significantly improved boost efficiency.
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Thompson Chevrolet
90o V8 n/a
255 cu in (4.2 litres)
16-valve pushrod
1963
Semi-stock
Thompson was back, now using factory-supplied all-aluminium Chevrolet Small Block base; again fuel-injected. Notable, as per his earlier Buick, was the use of a Schaller quarter-speed double lobe camshaft.
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Ford Indy V8 pushrod
90o V8 n/a
255 cu in (4.2 litres)
16-valve pushrod
1963
Semi-stock
Bill Gay, executive engineer at Ford Advanced Engines, headed the factory team that developed an Indy engine from the pushrod Fairlane iron block and heads. Aluminium block and heads using modified patterns plus magnesium oil pan. Quad-carburettor unit had gear drive for the camshaft.
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Ford Indy V8 DOHC
90o V8 n/a
255 cu in (4.2 litres)
32-valve DOHC
1964-68
Evolution from ’63 Ford
Factory progression retaining the Fairlane-derived aluminium block. Gear timing drive (in effect an extension of 1963 drive for camshaft and pumps). The new aluminium heads set exhausts in the valley and vertical individual cylinder intakes between the cam towers. Mechanical injection.
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Blown Offy
I4 s/c or t/c
168 cu in (2.75 litres)
16-valve DOHC
1966-80
Evolution of the Offy
Downsized from 252 cu in by Drake Engineering within Goossen-penned shorter monobloc with revised gear cam drive. Initially iron; aluminium after cooling redesign for 1968. Mechanically injected. Roots and Ai-Research (turbo) options. Roots version quickest in 1966; thereafter (refined) turbo engines stronger. Smaller bore for 1967 rules cut to 159 cu in. Limited to 2.7 bar from 1972.
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Pratt & Whitney ST6B-62
Turboshaft gas turbine
410 kW shaft power
—
1967
Adaptation of stock PT6
Developed by Pratt & Whitney. The ST6 was a variant of its PT6 created for use as a railway locomotive powerplant. The ST6B- 62 was the version the factory developed for Andy Granatelli’s STP-Paxton Turbocar; packaged by Ken Wallis alongside the driver.
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Weslake Ford
90o V8 n/a
303 cu in (5.0 litres)
16-valve pushrod
1967-69
Stock block
AAR/Weslake project to exploit the 305 cu in newly allowed for unblown stock blocks. Weslake aluminium heads on iron Small Block Ford with 9o (versus 22o) valve inclination, straighter shot porting and Weslake heart-shape chambers. Mechanically injected. Allowed 318 cu in for 1969.
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Pratt & Whitney ST6/76
Turboshaft gas turbine
370 kW shaft power
—
1968
Adaptation of stock PT6
The ST6/76 was a lower power version of the ST6 developed by Pratt & Whitney for Team Lotus following an enforced circa 40% cut in intake area.
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Ford Indy V8 Turbo
90o V8 t/c
159 cu in (2.6 litres)
32-valve DOHC
1968-78
Evolution of the DOHC Ford
Further factory development of the DOHC Ford as a de-stroked, smaller displacement still mechanically injected engine boosted by single Garrett turbocharger. Ford quit after 1970; rights bought by AJ Foyt.
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Brabham Repco 760
90o V8 n/a
256 cu in (4.2 litres)
32-valve DOHC
1968-69
Arguably clean sheet
See accompanying article for
full discussion.
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Yunick Small Block
90o V8 t/c
207 cu in (3.4 litres)
16-valve pushrod
1973/75
Stock block
Developed by Smokey Yunick and Ralph Johnson using classic iron block, pushrod Chevrolet Small Block, which was equipped with twin turbos. Mechanically injected.
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SGD Offy
I4 t/c
158 cu in (2.6 litres)
16-valve DOHC
1975
Evolution of the Offy
Developed by Drake Engineering, an Offy evolution having a 44o rather than 72o valve angle, re-ported head conceived by Art Sparks. This aluminium monobloc was penned by Goossen before he died in December 1974; Hans Hermann completed the design work. Mechanical injection.
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DGS Offy
I4 t/c
158 cu in (2.6 litres)
16-valve DOHC
1976-80
Evolution of the Offy
Devised at Drake Engineering by John Drake and Hans Hermann. A further development of the SGD Offy, now with 38o valve angle allowing a straighter, smaller bore intake port and flat top piston. Unlike SGD, the intake and exhaust ports now siamesed.
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Cosworth DFX
90o V8 t/c
162 cu in (2.65 litres)
32-valve DOHC
1976 onwards
Adaptation of the DFV
A derivative of the naturally aspirated 3.0 litre Cosworth DFV Grand Prix V8 developed initially by Larry Slutter and Chickie Hiroshima at Vels Parnelli Jones, subsequently by the factory, which modified the head. Used short-stroke crankshaft. Initially the same mechanical injection system as the Offy. Electronic injection phased in from 1987. Single turbo mandated by 1976 rules.
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AMC
90o V8 t/c
207 cu in (3.4 litres)
16-valve pushrod
1976-79
Stock and semi-stock
Fred Carrillo-inspired;
Champion Spark Plugs’ Dick Jones developed this as an affordable engine. De-stroked from 343 cu in Trans- Am iron block and heads; flat-plane crankshaft. Aluminium block and heads from AMC in 1978. Mechanically injected; enforced single turbo.
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Chevrolet V8
90o V8 n/a
355 cu in (5.8 litres)
16-valve pushrod
1979-83
Stock or aftermarket block
Various developers took advantage of a new rule allowing unblown stock blocks 355 cu in. AAR and Ed Pink were in the forefront using a Donovan aftermarket block and new GM aluminium heads. Mechanical injection. Roger Rager qualified one he built himself using a school bus-seasoned iron block!
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Chevrolet V6
90o V6 t/c
207 cu in (3.4 litres)
12-valve pushrod
1980/85-88
Semi-stock
Ryan Falconer created the first Chevrolet stock block V6 turbo on behalf of GM for 1980. Factory-developed iron block and aluminium heads. Mechanically injected. Returned in 1983 with a splayed valve version for Foyt that didn’t qualify. Foyt subsequently developed his own, without success.
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Chevrolet V8 Turbo
90o V8 t/c
209 cu in (3.4 litres)
16-valve pushrod
1981
Semi-stock
After AMC pulled its support, Dick Jones took his turbo stock block project to GM, redesigning it around the Small Block Chevrolet. No compromise with GM casting an aluminium block, and Brodix supplying aluminium heads. Still 180o crankshaft and mechanically injected.
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Buick V6
90o V6 t/c
207 cu in (3.4 litres)
12-valve pushrod
1984 onwards
Semi-stock
Initially developed on behalf of Buick for the Indy 500 by McLaren Engines. Used factory Stage II high-strength iron block with option of iron or aluminium heads. Initially mechanically injected, later electro-mechanical. Electronic ignition control from Buick.
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Pontiac Small Block
90o V8 n/a
383 cu in (6.3 litres)
16-valve pushrod
1984
Stock block
Naturally aspirated stock block dispensation now up to 390 cu in; developed by AAR. Mechanically injected it used the new Super Duty Pontiac Motorsport aluminium race heads on the GM corporate iron Small Block.
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Chevrolet Indy V8
90o V8 t/c
162 cu in (2.65 litres)
32-valve DOHC
1986 onwards
Clean-sheet engine
Designed and developed by Ilmor Engineering; the first at the Brickyard of the new-generation, purpose-designed engines. Ground effect-friendly layout, all-aluminium and fully stressed. Rear-end gear drive. Electromechanical injection; fully electronic for 1988. Fully described in RET 146.
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Judd AV
90o V8 t/c
162 cu in (2.65 litres)
32-valve DOHC
1987 onwards
Clean-sheet engine
Brabham Honda-badged; designed and developed by EDL, and supported by Honda, which cast the block in Japan. All-aluminium and fully stressed. Rear-end gear drive for DOHC, initially operating through finger followers later direct via bucket tappets. Pioneering use of full EMS from Zytek.
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Porsche Typ 2780
90o V8 t/c
162 cu in (2.65 litres)
32-valve DOHC
1988 onwards
Clean-sheet engine
Purpose-designed by Porsche with no direct link to any other factory engine. All aluminium, fully stressed and aero-friendly slim bottom end. Front-end gear timing drive. First known use of oil gallery pistons at Indy. Full engine management system from Bosch.
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Cosworth DFS
90o V8 t/c
162 cu in (2.65 litres)
32-valve DOHC
1989 onwards
Evolution of the DFX
Comprehensive factory revamp of the DFX retaining only block, crankcase and geartrain. New heads, albeit retaining 32o included valve angle. All other mechanicals new, and new bore and stroke. Last DFX Indy win in 1987 had been using mechanical injection; Cosworth now fully electronic.
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