I thought they banned the A9X homologation, and forced the cars to be run as SS hatchbacks hence the smaller valve engine, rear drums and no rear spoiler or bonnet scoop. Not sure if this affected sedans though? The smart thing to do would be to have run an L34 again, so kept the L34 engine but got to have the T10 and 10-bolt plus rear spoiler.

Yes, and it had a 10 bolt and T10 as well afaik. I had axles in my LX hatchback Salisbury that came out of that 1980 car.

I think that is someone putting 2 and 2 together and getting 5.5. I think it means the original 1973-4 engines that were allowed to carry through to 1979 were no longer allowed. So the manufacturers had to use engine components as fitted to the later 70’s production cars. The avenue to get international FIA homologated engines into GroupC must have been used to get a high power 350 into the Z28’s and also the hipo Celica engines amongst others.

Think I may have found the confusing rule change for the valves.

1979: Valves must be of the original dimensions.

1980: Valves must be of the the same head diameter and seat angle as the standard component.

Am unable to find any differences in the 1979 and 1980 Group C rules that would explain why the A9X Torana could not run rear discs, rear spoiler and bonnet scoop in 1980.

What fuel were they running ?

If they were running pump Super fuel anything over 10.5:1 would of lost power.

Why change let a piston be free like that and come down on a cam chain that had to be single row when they were double sprockets, if I remember correctly Brock and all were totally pissed off about that in the VC Commodore.

If I remember correctly Dickie boy was running a Heavy Duty XE194025 ? Block in the XD-E but for one that blew up the day before the race and he had to use his spare engine with the STD Block, as Dickie boy was saying that he was surprised that that engine lasted so well, also I thought that the VC Commodores were using L34 blocks as well.

I wonder how the cars would of went in stock form like they did back in the pre XA Falcon days when you turned up with street rego driven car, just tweaked with brake pads and a open Carby and dizzy tune and exhaust, engine blue printed and balanced and HD clutch and safety etc not to mention open wheel width spec but street rego tyres should of came into it, as that could of gave people a better idea to chose from, don't think you would of seen anyone running TA's.
As to the way I seen it, I see it from the road driven car point of view that one could buy and do street legal mods to aspect, as that way the race delivers road drivers a better deal to benefit from.
So lets say in 1976-7 what car would I chose 5.8L XC Falcon 4sp or T Bar, 5.0L HX GTS 4sp or T Bar with crap T400 or the LX SS or SL/R500 Torana 4sp or T Bar Trimatic but the weak banjo diff, well I think I would had to wait until March 1977 to get RTS and go for the 5.0L SS Hatch with T Bar and put 14in wheels on it directly and then deal with the engine to up grade that. I would have to wait until Sep 1977 to get a A9X with a good diff. but then the VB 5.0L 4sp came out late 1978 to get a better handling car.

I got The Highlights of Bathurst 1980 to 2002 I have seen to 1986 so far and I am not impressed so much with the information as such is more for the novice. the highlights ? I am more interested in the goings on, the 1973 HQ Holden with the 308 would of been of much interest to me and the 1974 350 HQ was as well, it was not so much only looking at who won, it was everything about the cars and the racing. I do not idolise the drivers I give them credit but it's the cars that are my main interest as any novice can flog on about a driver, sure that's of interest but it does not start or stop with just that aspect, Brock would of never truly won as many races that he did if he did not have the ability to steal a car and calling off the race because of a big smash is BS, because it's not called a 1000km race for nothing in my opinion.

They had to use pump fuel.

Pistons were free (within the allowed compression ratios) but cam drives (gears, chains, belts) were not. Just the way it was.
As far as I can see cam drives were never free throughout the Group C years.

I do not know whether an engine using 98RON fuel will lose power if the compression ratio is raised above 10.5:1 but I do know the LJ GTR XU1 static compression ratio stated on the recognition documents was 10.3:1 with a tolerance of +/- .5 which means the maximum allowable compression ratio for the LJ XU1 202 engine was 10.8:1
Betcha H.F would have used every last drop of that compression ratio if it was going to give them another 10th of a second.

Edited by user Thursday, 7 January 2021 1:30:51 PM(UTC)  | Reason: Not specified

Actually 1968 was the 1st year in Group E when exhaust systems were allowed to to be varied after the point of entry into the first muffler, but only if the Supplementary Regulations allowed.

1980 was the 1st year in Group C the complete exhaust system was free.

Edited by user Friday, 8 January 2021 6:47:56 AM(UTC)  | Reason: Not specified

Having done some research on KB's Camaro it appears that the CAMS were correct to not allow him to race with disc rear brakes.
Under FIA Recognition to Group 1 GMC never homologated (built 5000 cars with)the J56 disc brake rear end for the Camaro.

RPO J56 - Heavy Duty rear disc brakes were however allowed to be used in FIA Group 2.

The CAMS recognised the Camaro for acceptance into Australian Group C based upon the FIA Group 1 recognition, therefore any parts homologated for use in FIA Group 2 were not allowed to be used in CAMS Group C.

FIA Recognition 5310 states RPO J56 Heavy Duty Disc brakes, which gave you disc brake rear axle assy as well as the heavy duty front discs & calipers.
No mention on the recognition documents of JL8 only J56.