F1/F5000 conversions - and vice versa ?
Posted 01 October 2000 - 17:27
a March 731-Cosworth 3.4 in the 1975 European F5000 series.
Hunt`s 1973 Hesketh car, Autosport said. The Hunt machine
was 731-3 but Paul Sheldon stated the chassis number of
Hayje`s F5000 as 721G-3 (ex-Peterson 1972?). Who is right?
Then there is Beuttler`s 721G-2. Did Bob Lazier race this
car in F5000-spec. in the opening two races of the 1973
US series ?
Were the Surtees TS 7/9 F1s ever converted into TS 8/11
F5000s ? TS 7/TS 8, TS 9/11 looked very similar.
What about Posey`s 1971/1972 USGP Surtees racers ?
Who knows more F5000/F1 conversions ?
And vice versa ?(or was the F5000 Mclaren M25 the only one ?)
Posted 01 October 2000 - 20:22
The 721G-02 can hardly have been used as an F5000 in 1973 because it was rebuilt as 731-02 for Beuttler's use from the Spanish GP (Apr 27-29) onwards till the end of the year.
The Surtees TS8/11 probably shared the same tub with the TS7/9 but were no rebuilds as far as I know.
Posey drove a third works Surtees (TS9-02) in 1971 after he won a "shoot-out" for the drive between him and Gijs van Lennep in practice. The following year he hired TS9B-06 from the team for his private entry.
Posted 02 October 2000 - 10:20
Kevin Bartlett drove the Brabham Lee Seaton (from NZ) owned in 1978, a BT43 fitted with a Chevy, and it was in some of the same races as McCormack in that year. Allan Hamilton fitted a Chevy to a McLaren M26 as well, Alfie Costanzo winning the series in 1981, I think.
Out of synch with these was the Des Lascelles Cooper, a 1961 or so car with a Ford 289... still a F5000, I guess, but not very competitive.
Now, I wonder if you can really call the cars fitted with Cosworth V6s F5000s?
Posted 02 October 2000 - 10:27
Fast That’s Past – McLaren M23 Leyland
by Ray Bell
AS JOHN McCORMACK chased Graham McRae down the straight at Sandown in 1973, the rear end of his car sagging at one side, he was hating his Elfin MR5. A broken bolt in the rear suspension cost him that Grand Prix, despite his courage in fighting McRae to the finish.
That dislike for Elfins finally manifested itself in the appearance of the McLaren M23 in 1976. In between there had been a smaller, lighter Elfin, the ML6, which came into being early in 1974. McCormack was looking to overcome the extreme rear weight bias of the F5000 by using the Leyland P76 engine and Repco were happy to work on the development.
Developing cars was as much a point of this driver’s racing as the driving. It was, in fact, the part he enjoyed the most. And the part where bits broke and he ran into fences was the part he enjoyed least. Surfers Paradise, 1974, saw this happen when the front sub-assembly of the ML6 break and a wishbone came adrift. The repaired assembly was in for Calder, but cracks showed even before the race and the car was withdrawn.
Dale Konnecke was in charge of putting things right, so his choice to instal the Repco Holden engine was also followed. Repco Engine Development Company had closed, anyway, and further work on the Leyland engine would have to be done independently, making the Holden a good option for the time being.
In this form the MR6 took McCormack to his second Gold Star in 1975. Even with this success, the car failed to show that Garrie Cooper had translated the Tyrrell ideas (that led to its conception) into a real race winner. Only a change to Sports Sedan rules prevented McCormack putting the bits into a Corvair body he had acquired as its end neared.
The Leyland project was still proceeding, and the chassis chosen to carry it to completion was the ex-Formula One McLaren M23. Chassis No M23/2 was advertised for sale by South African Dave Charlton, and McCormack bought it minus engine.
In 1973 the M23 had succeeded the Ralph Bellamy-designed M19 McLarens that had been competitive in the World Championship, the Gordon Coppuck M23s going that step further by taking the marque’s first World Championship with Emerson Fittipaldi. They remained at the forefront of the McLaren attack until the bugs were ironed out of the M26 during 1977. Even then, the factory cars gave newcomers Gilles Villeneuve and Bruno Giacomelli their first taste of F1, and a privately owned M23 ran to the end of the year.
That put this model at the forefront of F1 racing for four and a half years, with James Hunt the second driver to win a World Championship in one.
McCormack’s purchase was made in mid-1976, and Konnecke and Simon Aram quickly completed the conversion.
For the September 19 Gold Star event at Oran Park the car sat fourth on the grid, but a valve broke on lap 22. A win followed at Calder, then at Phillip Island it had pole and led until a tyre deflated on lap 16. Even so, the car took third place in its inaugural Gold Star series.
One of McCormack’s aims in changing the car to F5000 was to keep it as original as possible. “The oil tank fitted in behind the back of the tub, and by removing this we had just enough room to accommodate the Leyland engine,” he told us. The front of the Leyland had many changes, however, to make it possible, including a shortened harmonic balancer and a relocated water pump.
The gearbox was the FG400, which had the same diff as the DG300 universal in F5000, but the lighter gears of the FT200 as used in F2 and Atlantics. In F1 these were marginal, and with the extra torque of the bigger engine they were too frail. Peter Holinger cut new gears with fewer teeth and a deeper root diameter, which proved to be ju-ust good enough. For the time being.
“The Leyland engine was only just strong enough to hold in the power (390bhp), especially when bored out to five litres,” McCormack added, “so we couldn’t use it as a stressed member.” Two subframes took the major loads, linking the clutch housing to the original pickups on the tub, while diagonal braces came from the radiator pods to a central point under the gearbox to give lateral rigidity.
The M23 was unusual in having fixed length driveshafts. The minute variation in length ordinarily taken up by a sliding spline (which can be subject to binding and hence affect handling) was not addressed in the shaft, but within the upright. The outer quarter shaft ran in Torrington bearings that allowed them to work in and out as the suspension experienced its travel.
Cornering loads were thus fed through the driveshafts to the sideplates of the differential housing, reducing loadings on the suspension joints.
John considers that this gave the car less feel, but “. . . it was always very stable, in fact, it never broke away. I never spun that car.”
With the original high airbox of the early M23s, the car looked just as it would have done in F1 trim. Much like it did when Peter Revson used it to give McLaren their first home GP win at Silversone in 1973. Except of the Yardley colours, which were covered up with the orange of Budget Rent-a-Car for the 1977 season. Wheels remained original, too, one reason for taking this path being to use F1 rubber.
The Rothmans International Series brought no success, three finishes in lowly places, but with the first round of the Gold Star at Surfers came a win. Round 2 at Sandown was a disaster, for the car’s tricky cooling system had to be carefully bled. A problem on the warm-up lap was diagnosed as this not having been done correctly and thus the car was caught out in the pit lane as the race started.
For the final round at Phillip Island (the Gold Star was at a terribly low ebb) the car showed its true pace. Two seconds a lap quicker than the best Lola, it was a moral to win if it could finish. It had the race well and truly won with three laps to go, but then the engine’s inherent weaknesses caught up and John pitted for the final two laps. He came out to cross the line when the flag fell, clinching the Gold Star Championship for the third time.
Wrapping up the year was the Rose City race at Winton, and this fell to the McLaren handily as its weight and balance advantage really showed up.
Two failures to start in the 1978 International series were followed by another first round win in the Gold Star, this Oran Park race featuring a stunning round-the-outside-pass on Kevin Bartlett. Round 2 was Sandown and another AGP, that dreadful race that saw disastrous crashes and cars dropping like flies.
The McLaren was virtually out before the start, having been hastily fitted with the only set of head gaskets available after a problem developed. These didn’t have the necessary water holes to let coolant into the block, so overheating was inevitable. It held second place until its early retirement.
Sponsorship was now from Unipart, reflecting the Leyland part of the package, and they would have been overjoyed with the domination of the field at Calder. Until it ran out of fuel with a lap to go. McCormack was second in the Gold Star.
Again the season closed with Winton, this time James Hunt being invited to drive the latest Elfin, the MR8. The McLaren was second on the grid and the only car likely to cause the ex-World Champion any trouble, but on the fresh surface a stone flicked up and jammed in a brake caliper on the first lap. A pit stop to bleed the rear brakes and removed the stone cost almost a lap, so John rejoined ahead of Hunt and stayed there the rest of the race to claim fourth place.
Big things were being cooked up behind the scenes while all of this was unfolding, however. To address the lack of power, new heads were designed by Phil Irving and cast from a special alloy from Comalco. Called a ‘hypereutectic’ alloy, it had a high silicone content and other constituents affecting the micro-structure of the material during heat treating.
Comalco were working towards eliminating valve guides and seats, and thus these heads had none. The design also featured a ‘bent’ pushrod, with a shuttle running in a bush in the head between two short pushrods to allow more room for straight inlet ports.
Exhaust ports were much better than the original head’s, and Irving used Heron-type bowl in piston combustion chambers. The flat head surface also helped in another area – the face was made thicker to give extra strength in an area of the engine known to be weak.
Initial dyno endurance test runs were stopped regularly to check if there was any creep in valve height (measuring at the tip of the stem), with one power run showing that there was 420bhp and 420ft lbs of torque. This latter figure was sensational, being about 40 higher than the Repco Holdens, renowned for their mid-range. A revised cam (a Wade 224A used on Holden sixes) returned 470bhp and 380 ft lbs.
First time out for this engine it met opposition from the Chev runners. It was because of persistent head cracking of the Chevys that the rules had been relaxed to allow non-standard heads, but they weren’t expecting valves to operate at a different angle. CAMS ruled in favour of the IMC (Irving, McCormack, Comalco) heads.
But it was of no consequence, for the head gaskets failed after 25 laps in the Sandown race. Their only other outing was at Surfers, where the car caught fire on the warm-up lap after practising eighth fastest. They were never used again.
Why? “They gave so much power that they cracked the block,” McCormack remembers. The car ran worn original heads at Adelaide and overheated, then put in a good performance at Oran Park to challenge the later F1 Wolf of David Kennedy for many laps before retiring.
Then came the AGP at Wanneroo, and another weakness showed up. Exiting Coca Cola corner on the first lap of practice it broke a gear – and the replacements as the day wore on. “In flat running they did the job,” John says, “but here you climb out of the corner and the load was just too much.” The traction being so good there would also have contributed, and a sticky throttle in the race made for an early exit.
That year the US CanAm series was for F5000s with bodywork enclosing the wheels, so John decided to sample it to see if it was viable. “There was so little racing here I couldn’t make ends meet, so I had Simon design a body and it was built by John Webb,” he recalls.
The rules also allowed different engine capacities with a formula for weight variation. Two short stroke cranks were made and the engine brought back to 4-litres so they could run at 1300lbs, with three events (Mosport, Watkins Glen and Mid Ohio) being the sum of the effort.
The car returned to Australia and was mothballed, John’s interest in building the Jaguar Sports Sedan taking precedence. Then Unipart called and wanted representation for a new car polish at Calder for the mixed-grille F1 and F5000 AGP of 1980. The Gold Star was effectively dead and the International Series a memory as F5000 died out, but this event saw them have a final fling.
The McLaren didn’t make it, however, John having been injured in a road crash en route to Calder and put out of action for some time.
“I put the car under the house, then a few years later McLaren rang up and wanted to buy it,” he says. The car was rebuilt in DFV form and went to the Donington Museum.
The engine project also became a museum piece. “Phil Irving suggested that I contact Morgan to use them on the Plus 8s,” he told us, “but I didn’t want to get into the engine building and selling business. We only ever made six heads.”
The M23 was a great car let down by frailties that should have been able to be overcome. Its speed in fast corners was fantastic, it being visibly faster than the tail-heavy cars it raced against, and its few successes were gained against adversaries with much more power.
Finally, however, it was let down by the inability of the competitors to keep up with the demands of running the cars that made up our best-ever racing formula. For 1981 the Gold Star was over almost before it began, another McLaren, the M26, being kitted out by Alan Hamilton for Costanzo to win. Before the end of the year the Formula Atlantics were stealing the limelight with a series of their own, and F5000 came to an end.
Posted 02 October 2000 - 15:39
721G-2 because of an ad of Can-Am Cars Ltd. (see http://www.hemmings.com/dealers). "Previous owners in the US;
Tempero, Lazier and Gustafson", the ad says. Lazier ran
a March in the 1973 Riverside and Laguna Seca F5000 rounds.
Then he switched to a Lola T330. I think his March racer
was the 1973 F5000 model(73A).
Cannon`s F5000 March was the ex-Skip Barber 73A , I believe.
He ran the car in the final 1974 US-races for the first
time. In 1975 he put some March 751 body panels on his
racer. Looked like Brambilla`s orange F1 machine !
Sorry, Ray I just did not remember my own Mclaren M23-
Leyland/Mclaren M26 threads...
The Cosworth 3.4 was a good attempt to save F5000 in
Europe in my opinion. The Cosworth-powered cars of Purley
(Chevron B30) and Jones (March 751) were quite evenly
matched to the VDS Lola T400-Chev. of Gethin and Pilette
in 1975. Even Tom Walkinshaw ran a March 751-Cosw. 3.4
that year !
Posted 03 October 2000 - 10:59
Does that have any relevance in the Formula One of today?