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castellan Offline
#41 Posted : Friday, 12 October 2018 10:19:12 AM(UTC)
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Originally Posted by: HK1837 Go to Quoted Post
Originally Posted by: castellan Go to Quoted Post
Originally Posted by: Ausjacko Go to Quoted Post
Anyone have a clue why they made the HG 350 with only a 2 speed power glide?


They had 3sp autos in the USA in small block Chevs, so yes they could of done so, but it cost more.


They had a TH400 but it would never have fitted the old HD-HG floor pan. The new TH350 was only introduced in 1969, and the HG was well locked in by that time.

Closer to the truth will be fact that the HG isn't truly a different model, it is more of a "SeriesII HT". It was only created as GMH thought the HT would end up running for way too long as the HQ was delayed terribly by GM US's decision to have GMH kill off the HK based HQ and replace it with a US design, which GMH had to finalise. Thus the "gap filler" HG was created.

If you ignore the softening of the HG (examples removal of stainless, the softer nose and tail-lights and softening of suspension in more variants) there isn't all that much difference between a HT and a HG. Sure GMH's rejig of the European TH180 into the Trimatic was part of HG, but it was probably destined to be introduced with HQ anyway.

At the end of the day, the amount of re-work to fit a TH400 for less than 200 cars only for HG wouldn't be worth it. Plus the cost would be prohibitive and it is unlikely that the GM parent would even supply the TH400 transmission for the LM1 engine in that size car anyway. TH350 yes, but it wasn't available when the HG was designed.


Right you are.
HK1837 Offline
#42 Posted : Friday, 12 October 2018 10:36:58 AM(UTC)
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Originally Posted by: castellan Go to Quoted Post
Originally Posted by: HK1837 Go to Quoted Post
I guess it depends on whether the HT 308 GTS was standard spec or optioned with dual exhaust and maybe with 3.36 rear axle. An early HT 5.0L GTS (307) with dual exhaust was a quick car as from memory it was standard with a 3.36 rear axle. The automatic HT 350 was pretty quick too.


HT-G GTS 308's all have dual exhaust and std 3.36 diff and XT GT have 2.93 diff, but I am sure that the HT-G GTS 308 auto or manual would hose of a XT GT, but for top end, but a 3.08 ratio would still eat a XT GT I am sure.

HG GTS 308 trimatic auto would be a quicker car than a GTS 350 auto.Shhh


I'm pretty certain the only HT-HG with standard dual exhaust was an 81837. It took until the HX GTS before a Holden V8 was standard with dual exhaust, although the HQ SS got a dual system (and 3.36 rear axle which made a standard HQ GTS 308 very surprised).
Correct, HT-HQ 308 auto rear axle ratio was all 3.36 standard fitment.

I agree a dual exhaust manual 307 or 308 HT or HG would be close to an XT GT, but the single exhaust versions no. Wouldn't take much to quicken up an XT GT though as it had 10:1 compression and was a nice motor. 3.25 gears and a Quadrajet or 600cfm Holley and it'd be far quicker.

HT-HG GTS350 auto were not a slow car, they were still a tad over 9:1 engine and the only difference between this engine and the manual car was the head chamber sizes and 2 bolt block rather than 4 bolt. Valves, intake, carb (other than vacuum source for dizzy), dizzy, cam, pistons, crank etc all the same. They did have a 3.08 rear axle as standard but 3.36 was optional. In fact the Press were very impressed, even more so when they timed these (with air and/or steer) to be not far off the manual cars, without knowing that GMH had hidden the manual car's true performance. A standard HT GTS350 auto optioned with A/C and power steering as tested by the press at the time managed 16.0s 1/4 mile @90mph, 117mph top speed and 0-100mph is 22.0s. This was letting the auto do its thing, not manual shifting. Apart from the top speed limitation of the auto transmission that is pretty much line ball with an XT GT as tested by the same methods by the same people and faster than the automatic GT. The XW GT auto would have easily had its measure though, but may have got a bit of a shock coming up against one optioned with a 3.36 rear end and no air or steer as that would be a significantly closer match.

Edited by user Friday, 12 October 2018 3:17:09 PM(UTC)  | Reason: Fixed rear axle ratio for 308 auto HT-HG

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Warren Turnbull Offline
#43 Posted : Friday, 12 October 2018 2:07:43 PM(UTC)
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I am not sure why the ARDC was so anal about the rear axle ratio thing. I do know they were very anal about cars being produced and to some extent being identical. Dealers were told to register their demonstrators so that they could be checked to have "sold" so many. But you would thing options like reclining seats, axle ratios etc would be overlooked.

This is most likely why the very limited identical build of later models would have come about.

Lets not forget the very published account of the XY phase III 15" globes with the ARDC checking all owners had received a set, the last being an owner in Tasmania from memory.
HK1837 Offline
#44 Posted : Friday, 12 October 2018 3:01:03 PM(UTC)
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And the reclining versus fixed bucket seat thing Warren, very odd. Luckily tyres were free or they'd be after 200 cars with the same diff ratio, same seats backs AND same tyres! Imagine if all Salisbury units weren't LSD? Or if the HK Kingswood raced had an LSD or an alternate rear axle ratio as well as 186S, 4spd and reclining bucket seats? GMH found over 200 of these cars with standard rear axle, but my guess is the same thing with LSD or 3.08 rear axle would be lucky to be a handful of cars made.

Edited by user Friday, 12 October 2018 3:03:41 PM(UTC)  | Reason: Not specified

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8D11PCH2 Offline
#45 Posted : Friday, 12 October 2018 8:01:06 PM(UTC)
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Originally Posted by: abi Go to Quoted Post
One thing you will notice in old photos is all the 327s (and GTs) at Bathurst run the stock exhaust all the way to the rear including the quad tail pipes and at other events such as Warwick Farm and Oran Park they exit at the side under the door. This would be due to ARDC vs CAMS rules.

Cheers Adrian


Hello Adrian,

The The C.A.M.S National Competition Rules (NCR) 1968 Appendix C, Group E Series Production rules, Appendix 3(m) "Exhaust systems may, if permitted by the Supplementary Regulations, be varied, but only after the point of entry of the engine pipe into the first muffler".
This was a new rule introduced in 1968.

Obviously the ARDC Supplementary Regulations did not allow any modifications to the exhaust system whereas other clubs did at their sanctioned competitions.

Edited by user Saturday, 13 October 2018 9:25:25 AM(UTC)  | Reason: Not specified

Ausjacko Offline
#46 Posted : Tuesday, 16 October 2018 8:56:02 AM(UTC)
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My question was more to why they did it, not the choice of gearbox. Was it do to with the homologation being spoken about here?

Originally Posted by: HK1837 Go to Quoted Post
Originally Posted by: Ausjacko Go to Quoted Post
Anyone have a clue why they made the HG 350 with only a 2 speed power glide?


What else would they have fitted?


HK1837 Offline
#47 Posted : Tuesday, 16 October 2018 9:06:58 AM(UTC)
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No. There was no other available gearbox for HG350 auto when HG was finalised.
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