1988-1992 Sierra Cosworth RS500 Turbo Group 'A'

~ Glenn Seton ~
Chassis number 155

SOLD - 16th July, 2010

Seton takes Sandown Park (Vic) victory 1990

Seton takes Sandown Park (Vic) victory 1990.

After two years with Fred Gibsons "works" Nissan team in 1986-1987, young but very experienced Glenn in his early 20's and his father well respected race engineer/driver and Bathurst winner Barry, set up their own workshop in Dandenong (Victoria) and in 1988 imported two factory prepared body shells from Ford Competitions Department in England, one of which is chassis no. RS155 being part of a homologation build of 500 cars required to be built to be eligible for Group 'A' saloon car racing worldwide.

The car was then constructed in their workshop using Harrop suspension components including hubs, drive shafts, axles, uprights etc. where permitted within the rules. Barry built the two litre Pinto based wet sump 4 cylinder 16 valve twin cam engines employing a Garrett modified M24 turbocharger with a large intercooler producing up to 2.4 bar of boost (over 30 lbs.) and around 580 horsepower on around 6.2 to 1 compression ratio with nearly 500 ft. lbs. of torque depending on boost settings.

A competition 5 speed Getrag gearbox was initially used but later a 6 speed locally made Hollinger stronger "crash" box fitted to overcome "turbo lag" between gears and offer more ratios at the circuits.

Weighing in at a regulation minimum of 1200 kgs including ballast, the Sierra was fitted with 17 x 8 inch BBS wheels initially and later in their development used 17 x 9 inch 5 spoked specially constructed Dymag magnesium alloy wheels (for Sierra's), which allowed larger tyres to be fitted. With their enormous "sudden" power around 6500 RPM, race Sierra's needed as much rubber on the road as possible. Also installed is a solid under-floor mounted aluminium case lightweight differential that is cross braced by the simple but "busy" internal roll cage/body stiffness chassis, which ran with a spool centre (locked), separate oil cooler, auxiliary pump and used multiple standard Ford 9 inch ring and pinion sets for circuit ratio changes.

Braking is handled by large ventilated 330 mm AP disc rotors front and 300 mm rotors on the rear both with 4 spot AP calipers with a cockpit graduated bias adjustment control and a digital readout.

A 120 litre bladder fuel tank is fitted with dry-brake attachments for fast filling and safety in long distance races. Avgas fuel only is used.

The body is all steel with fibreglass attachments such as front splitter, rear bumper and rear wing but the cars internal include a basic but modified dash, door padding, a special lightweight fibreglass race seat and 5 point race seat belt harness and of course there are multiple gauges advising turbo boost, revs, diff and engine oil temperatures, volt and amps, water temperature and so on.

Engine management was initially handled by a Zytec EMS computer but later replaced by a much more user friendly Autronic system which allows the cars engineer to easily download to a laptop using a co-ax cable, analyze the engines behaviour, fine tune at any time when the car is stationary making adjustments where necessary.

When raced in Australia between 1987 and 1992, all the Group 'A' RS500 Sierra's were rev-limited to 7500 RPM with an additional "black box" installed on all cars by CAMS (Confederation of Australian Motor Sport - the controlling body), to avoid excessive revs and subsequent engine "blow ups" but with the boost turned up to 2.5 or 2.6 bar done in some cases by others to achieve over 600 bhp but without caution the Sierra's were known for their engine unreliability. Many Sierra's were timed at over 300 kph (200 mph) on Bathurst's notorious Conrod straight especially during qualifying!

Close racing at Mallala (Adelaide) 1991

Close racing at Mallala (Adelaide) 1991

The English/European Group 'A' RS500 race cars were in some ways different in specification but still complied with the same rule structure and I had the benefit of meeting Andy Rouse multiple British touring car champion at Goodwood Festival of Speed (UK) in July 2001 and he was competing in demonstration runs with his 1988 BTCC Sierra RS500 in full race trim. He said "... I was surprised at the interest in the car as a genuine example and there were few real ones left most of them being substantially modified for other classes for display cars with dubious history's where some of the junk bits from under the bench at the back of the workshops have been bolted into straightened out unuseable old scrap shells and appropriately painted up to appear to be real."

Sadly this also is the case in Australia and a few cars have appeared at auctions or been sold privately to the unsuspecting amateurs who think they are buying one of Peter Brock's (or who-ever's) old Sierra for peanuts...wrong! There are very few "real" ones left in Australia but it must be noted that although UK & Europe discontinued Group A at the end of 1990 in favour of SuperTourer spec cars .... Australia/New Zealand continued with the class until the end of 1992 and there were some major specification (homologation) upgrades to the cars in this last two year period. This car received all of them.

There will never be any more Cosworth RS500 Sierra's built least of all in full race trim with genuine body plates and credentials and very significant racing history's as has "Glenn's own car" chassis no. RS155, original log book no. V7467 issued on 19.05.89 which I have.

The photographs here show the car as raced by Glenn Seton in Peter Jackson livery until it was purchased by me to run at the 1992 Adelaide Grand Prix Group 'A' support races and subsequently raced by me mainly in NSW at State Championship meetings under the umbrella of "sports sedans" as Group 'A' had been replaced with a 5 litre Holden versus Ford V8 category now called "Supercars!". To retain the absolute originality of this car, we never altered it's specifications in any way and even our own sponsor signage was sympathetic with the original Peter Jackson style. It has now been returned to Peter Jackson/Glenn Seton livery.

We raced the Sierra again at Adelaide Grand Prix in 1994 "anything goes Thundersports" support races and at Indy Surfers Paradise in March 1996 then later at Sandown Park in September 1996 with great success especially considering the opposition which were space framed/glass fibreglass bodied silhouette race cars with 6 litre fuel injected Chev. engined V8's, 14 inch wide wheels and weighing around 850 kgs. Setons Sierra was retired to be kept as an interesting car with a great history maybe of some value one day.

As it has an internal jacking system and it has been kept off the workshop floor, started, brought up to temperature and run up the gears to be kept lubricated religiously every month for the past 5 years. This is an important storage procedure...others take note! After a thorough check-over by John Masala in our workshop at Hornsby, it did some fast laps at Eastern Creek on 10th August 2001 as a shakedown with zero problems for it's participation at the HSRCA annual Historic Eastern Creek meeting 7/8/9th September where we were invited to do some "special" demonstration laps and asked to show the car in their on-track marque. Nobody has forgotten the Group 'A' Sierra's...they were an icon of the late 1980's and early '90's!

Effective 2006 CAMS (the official FIA body of Australian motor sport) placed Group A cars up to 1992 specification under the "historic umbrella" thus they are now eligible to race at all historic race meetings but must be presented in exactly the same specification of their era. Replica's or cars of dubious history are banned together with today's modifications to engines/electronics/all mechanical and body components etc and every car must have been extensively inspected by specially appointed scrutineers before a log book to race and a "Certificate of Description" similar to FIA papers are issued. There is no room for "cheats' in this category.

Even the signwriting on the car must be as it was in it's time. You may note however a slight change which has been approved to "PETER JOHNSON" as opposed to the cigarette advertising it used to have ... this has been done so as not to offend anyone and comply with today's tobacco advertising laws.

You will note in "scrapbook" below some new photographs of the car both at Eastern Creek (NSW Muscle Car Masters Sept 2007) and a month later at the Sandown Park (Melbourne) huge historic meeting where we gained pole position and a win ... but unfortunately a DNF in the last race due to a faulty $30 radiator cap of all things!

The second engine is now rebuilt (freshened up) and we intend to race the car again seriously in 2008 so will update this site as we go.

THANK YOU for your interest in my now "very rare and valuable" car ...

UPDATE 26.05.08 ...

WINS at Sandown Park (Vic) Nov 2007 plus pole position and lap record plus 3 x wins at Phillip Island (Vic) March 2008 ... probably Australia's fastest Group A car racing today and will be racing at Muscle Car Masters (Eastern Creek Sept 2008 plus Sandown Park in November) if not sold beforehand.


Rob Tweedie's first outing at AGP 1992 in good company

Above: Rob Tweedie's first outing at F1 AGP 1992 in good company (Dick Johnson's new 1993 spec Falcon).


Above: Eastern Creek 2007 leading the field


Above: Sandown Park end 2007 included a lap record


Above: Sandown Park 2007


Above: Eastern Creek 2007


Above: Eastern Creek 2007


Above: The "best" view


Cars I have previously owned: (click)

F304 Dallara Formula 3
1956 Jaguar 'D' Type
1958 Porsche 356A
1960 Gemini - Formula Junior (FJ)
1962 Lotus 23
1963 Austin Cooper S
1965 formula 2 Lola T60
1971 Porsche 911S/T 2.3
1977 Elwyn (002)
1990 Sierra Cosworth RS500 Turbo Group 'A'
1988-1992 Sierra Cosworth RS500 Turbo Group 'A'

Biography of Robert Tweedie

The 'Current' Car Collection

For Sale - historic 1850's Hunters Hill (Sydney) residence


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