63 replies to this topic

[WhiteA9XS]

Race XU-1's used on tarmack circuts would use the 55- 91 XJ cam, the street versions generally did not, because they did not comply to some state laws about the idle quality or speed, WA laws were strict on this.
Street going XU-1's had the 44 - 88 XH camshaft and this quoted in the parts books if a person was in the know with the right contacts they could have the bigger XJ camshaft fitted at their expense.

Think there was a lighter flywheel too, and appart from the freedoms alowed under CAMS rules most other things were the same.

1973 was the first year of group C rules , this allowed freedoms of camshaft and other items such as carbies (retain existing number of venturies as previously mentioned) , wheels , etc , so the race teams could use any grind they wanted to use . the XJ camshaft was developed by wade cams for HDT , you can find the 1973 group c rules on the group c website .. click on 1973 PDF in first post . http://www.groupc.or...wthread.php?t=3

Edited by WhiteA9XS, 06 January 2012 - 07:20 PM.

[enderwigginau]

These factory race specials probably only amounted to a few red and white cars.........

[Dr Terry]

Thank you I have had those rules for a few years now, however I am now understanding them better.
Can you please shed any light on why we are discussing rules that the XU-1 raced under in 1972 while the XU-1 raced under group D rules in 1973?

My understanding is that under 1972 Group C rules this was based on purchase price, whereas the 1973 Rules ( C & D ) were based on cubic capicity.
In 1973 the XU-1 was over capacity for the group C rules only a couple of GTR's raced in this up to 3 litre category.

The 1973 LJ XU-1 was racing in the group D class by the entrant list documents which is 3001 to 6000 capacity.

Have I missed something or is this just another case of people missquoting termalogy?

Mike

Hi Mike.

As oz772 has mentioned, I think you are confusing the race category rules with the class groupings. There was no Group D racing category.

Up to 1972, the 2 main sedan categories were Series Production & Improved Touring, there were others but these are the main two which concern us. Series Production at Bathurst was run under ARDC rules & was run in 5 classes (A, B, C, D & E) according to their retail price (up until 1971) & for 1972 only, they ran in 4 classes using a complicated formula of price multiplied by engine capacity (A, B, C & D).

Prior to 1973, the ATTC saw cars from the Improved Touring category like Mustangs, Camaros, Monaros etc, with certain modifications allowed. I believe these cars ran in classes sorted by engine sizes.

From 1973 onwards, both Bathurst & the ATCC were run under the CAMS Group C rules in 4 classes according to engine capacity. Most of the old Improved Touring cars were allowed even more modifications & became Sports Sedans. So 1973 Bathurst was run under Series Prod. rules in classes A, B, C & D, while 1973 Bathurst was run under the new Group C rules in classes A, B, C & D.

With your point concerning 'special factory race cars' I don't believe any Holden received special race treatment at the factory, prior to the run of A9X GM P & A shells which had extra spot welding & no sound deadening etc. The possible exceptions to this would the extra bodywork for the L34 & A9X flares which were done manually by outside contractors before the car's completion. Holden would not spend money to add sound deadening to XU-1 bodies on the production line, only to remove it later. HDT (& others) would have done this as part of their race preparation after the car had left the factory. While the cars' bodies had to remain 'stock' under the rules, a certain amount of tweaking (read blueprinting) was allowed to every area of the car.

Dr Terry

[frash da bucket]

Hi Terry,

I own one of these race prepared cars,much different to a road going xu-1 car,has lots of different mods that i have never seen on other torana's,its a 1972.

Cheers John.

Edited by frash da bucket, 27 January 2012 - 03:26 PM.

[Dr Terry]

Hi Terry,

I own one of these race prepared cars,much different to a road going xu-1 car,has lots of different mods that i have never seen on other torana's,its a 1972.

Cheers John.

Yes, John & there are many more like yours in existence today, but my point is that these mods were done post-production by the various race teams, not on the production line. There is no way Holden would have carried out special race mods on only those few cars that were destined for race teams. Their production schedule could not have coped with this. In each batch, all XU-1s were treated equally.

Dr Terry

[frash da bucket]

Hi Terry,

Im going to have a talk to don holland,he doesn't live far from me,he would know about these cars very well,my car was made early september and sold early november,so it must of been bought by a race team,i don't know who and the work was carried out in those 2 months,it could been made as a spare car for a race team,but wasn't used,and was sold off later to the dealer ship.

Regards John.

[REDA9X]

Holden didn't produce race special shells during the XU1 model. The first race special shell was the second Bob Forbes L34. This was supplied as a shell to Bob after they put the car in the lake at Sandown. Bob knew the production manager Mike Prose very well so they ran a new shell down the line and added some extra bits where Bob wanted them after his experience in racing the L34. After that, they used that experience to produce the A9X race shells. Any differences in race XU1's would be purely in team preperation.

[meanmachine72]

hey mike

dribble on dude dribble on
your research sucks and has holes in it like ya rust out police car!!

[Potta]

I reckon with Mike's logic I can definitely prove that the GTR-XU1 4DR was produced in secret without any external distinguishing features other than the fact they had 4 doors.

[Dr Terry]

Holden didn't produce race special shells during the XU1 model. The first race special shell was the second Bob Forbes L34. This was supplied as a shell to Bob after they put the car in the lake at Sandown. Bob knew the production manager Mike Prose very well so they ran a new shell down the line and added some extra bits where Bob wanted them after his experience in racing the L34. After that, they used that experience to produce the A9X race shells. Any differences in race XU1's would be purely in team preperation.

Hi Michael, was this was supplied to Bob Forbes as a bare shell, or as a complete car.

If it was just a shell, then it's fair to assume that ALL production XU1s, L34s & A9Xs (i.e. complete cars) received no 'special' treatment & it was only the bare race shells which were specially built for race only use.

Dr Terry

[frash da bucket]

Hi Terry,

I have been doing lots of reasearch on my car for 23 years,reading lots of books,magazines ,talking to drivers who drove these cars in the 70's,and had a good chat with peter brock at his last muscle car masters 2006 at eastern creek,who actually came and looked at my car for me,and showed me of different things that had been carried out on it,when it came off the production line.Maybe it was done some where else in the factory at the time,when these different mods were done and carried out.I would like to show you the different mods terry at all holden this year on the 5th of august,you can decide for your self.

Cheers John.

[xu2308]

John does your car have the A.B.S rear drum brake cooling fins cover, seems some of the LJ race type car had these on them

[frash da bucket]

Hi Al,

I do have the brake drums,with holes in it on the face,but not fitted on the car.

Cheers John.

[xu2308]

do they have cooling fins on the circumference part

[frash da bucket]

Yes they do al

[wot179]

Like these?

[frash da bucket]

Hi Craig,

Like them but a little bit different,mine have got cut outs on the face of the drum,you can adjust your brakes through the holes.

Cheers John.

[Dr Terry]

I don't believe they were fitted at the factory, but the ABS rear brake drums were an allowable modification under the 1973 Group C rules. As I understood, you could change the drum but not increase the brake lining area.

Not allowed though in 1972.

Dr Terry

[xu2308]

Dr Terry
if u get the Chevron Torana GTR XU-1 DVD and go to the menu and click on Bathurst 1973 and watch for a few mins, you will see the HDT LJ XU-1 pull up and thay take the driver side rear wheel off, get ready with the DVD remote and pause you will see the HDT Cooling Fin Brake Cover on the HDT LJ XU-1, Now a guy i spoke to that worked for A.B.S in Adelaide for years and years told me they made up 10 pairs for Harry Firths's HDT HQ for LJ Torana's