I’ve been told my HK prem is an early build because of the brake booster bracket
Did the bracket change ?
Tag says body 80569kR-03676-H5
Cheers

Edited by user Wednesday, 18 April 2018 7:09:39 PM(UTC)  | Reason: Not specified

Yes there were (at least) 2 different types of brackets. One fitted to ‘earlier’ cars is commonly known as an offset bracket where the rod through the firewall is at a different height to the centre of the booster. The other bracket is much simpler and not offset, the rod through the firewall goes straight to the booster. The bracket also pushes the booster further forward than the offset type. Couldn’t tell you when they changed sorry. If you google HK brake booster brackets you shoulf find images of both and links to other forum discussions pretty easily.

Some interesting info from Facebook (to HK, HT and HG Holden Builds) on early vs late booster brackets and when they changed.

Luis Santos ...When they tested them on the 327 before the race they found that bracket used to bend at full racing practice so gmh deleted that bracket adaptor to the later models including the 327 they made a straight shaft from booster straight to brake pedal. ...

Gordon Merrett My information was that in early HK they offered aircon with the 307 using pump and brackets imported from America suitable for LHD cars and initially they could not offer disc brakes with aircon. Drum brakes only maybe with the small booster. Answer hollow in the guard to move the booster over. Still not a lot of room so in HQ they moved the pump to passenger side where there was plenty of room.

Warren Turnbull Gordon Merrett Yes this is correct, the direct acting booster was introduced to allow AC on the 5 litre engine. Early 327s have been, AC Broughams were fitted with these right from the get go. Then they filtered across the range.

Richard Ewer Warren i have heard so much conflicting info on these boosters , i have a aug 68 built 327 it had a direct acting booster , i was in the process of changing it over to a offset booster as i was under the impression thats what it should of had, am i right in understanding that it should be direct acting ?

Warren Turnbull I had an August build car that had lever action but it was an early August as it was first regoed on the 20th. By the end of August both types were being fitted, so an August/September may have had either. They needed to fit both types, to exhaust current contract and to make enough of new ones (which all AC 5 litre had to have) for the new contract.

The brake pedal has an extra hole for direct acting, so check your brake pedal for signs of being changed before changing it.

Edited by user Wednesday, 2 May 2018 10:28:41 PM(UTC)  | Reason: More Info on early to late brake booster bracket change

Great, that’s some handy info

Do you know if there were any other differences with the early ones?

Really, what’s the go there?

HK20781S

Thanks for the great info HK, so if it’s made in June the booster bracket may not be original?or if it is it’s a rare series 1 booster and more collectable!

People make reference to series 1 and 2 HK Monaro all the time
I’m suggesting that this could be extended to the rest of the HK range

I agree

Would still be good to know what else changed during HK production
Tally so far :
1. Brake booster bracket
2. Door handle?
3. ?

There is heaps. Available colour and trim changed a few times. M21 4spd manual became available behind V8 across HK once Coupe production ramped up. M22 4spd manual made available at a similar time on commercials and both M22 and M21 available on certain 6cyl passenger models. Same with Salisbury rear axles on some model variants. Certain tyre options were added like Michelin XAS. 3.08 rear axle ratio added later in 1968, although I have never seen one. The brake booster changes already mentioned. The BODY tag moved from the firewall up to the cowl plate mid 1968. Console shift added to some model variants as an option or standard after coupe introduction. Rally wheels added later also. Sedan and wagon had adjustable bucket seats added as an option during HK. Door handles moved as already mentioned. There are others I can't think of right now, some added by GMH others forced by Regulation.

In HK (except Monaro & Brougham) the front interior lift-up door handle (& armrest where fitted) were moved rearward by 2.5-inches. This meant than the door trims were all altered & the door panel pressing was also altered, not to mention the linkage inside the door.

I'm not sure when this took place, but I think it was well before the Monaro/Brougham release date & was around April/May 1968.

Another production change for HK which comes to mind is the change from the round to oval shaped steering wheel (except GTS). This must have been veery close to the Monaro/Brougham release date, as I remember they made mention of the round steering wheel in the Brougham in one of the motor magazine stories of the day.

I think the brake booster change took place around August/September 1968. The reason for the change was that up until that point you could not option air conditioning & disc brakes on a 5-litre V8 HK, because the brake master cylinder plumbing fouled the air cond compressor. This became obvious with Brougham, because it had the V8 & discs standard & it was quickly realised that air con was to be a popular option.

The later style booster sat further back & closer to the guard & gave better clearance to the engine ancillaries, which made things easier when the HT 253/308 came along.

The other running changes I can think of are the new paint colour palette introduced around August 1968. Also the heater box went from light grey to black around April 1969. The early instrument had green lettering & this changed to white around May 1968.

Dr Terry.

Edited by user Friday, 20 April 2018 1:18:29 PM(UTC)  | Reason: Not specified