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supercoach24 Offline
#1 Posted : Wednesday, 20 January 2021 10:49:20 AM(UTC)
supercoach24

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so I am looking to add a little more oomph to a HT 253 V8.

I am planning on adding the easy stuff from the 308 but wanted to now if some of the stuff is hard to come by and if i am missing anything. I am going for a factory look, so not aftermarket parts if I can help it. Any help guidance appreciated.

factory OEM valley cover
QJet 4BBL (given my car is manual do I need to look for a HG coded carby, as for HT 308 was only available in auto)
New fuel lines
New heater hoses
New auto choke pipe
air cleaner element to suit the QJet Carby

Do I need to run or fit the vapour return line as per the factory workshop manual? as 253 did not have these from factory only 308/350

Edited by user Wednesday, 20 January 2021 10:50:05 AM(UTC)  | Reason: Not specified

HK1837 Offline
#2 Posted : Wednesday, 20 January 2021 11:20:47 AM(UTC)
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HT 308 did come in a manual, the carb is the same as a HG manual. Finding a ZA carby is still going to be hard though as a manual 308 was very limited in HT-HG. Plus you’ll have to retune the carb to suit a 253. You are best off using an XT5 blue 4.2L carby, which are also far easier to convert to electric choke so you don’t have to run the choke heat pipe. In these blue 4.2 carbs they are generic for auto and manual, whereas the HT-HG carbs you need a manual one. If you make the choke heat pipe right you can still hook it up to the blue 4.2 carby, and remove the operator off the HT-HG intake. You’ll pay up to $1500-2000 for a ZA carby, and possibly similar for a HT-HG 308 air cleaner. If you have the 253 air cleaner you could cut the base out of a Commodore air cleaner base and braze or silver solder it into the 253 air cleaner base, plus the tube for the choke fresh air supply if you want to run the factory hot air supply for the choke.

You can use a HQ to HJ 308 intake, just drill out and tap the hose connection on the front water passage.

Not sure about the vapour line.

I’d also get a cam ground to match a HJ-VL 308/304 cam and stand it upright like a HT-HJ 253 cam is. Leave the heads standard just with new springs. The other way to give it far more go would be to invest in a hydraulic roller cam and lifters. Crow cams should be able to design one for you to suit.

Make sure you get a new oil pump or at least rebuild the original properly.

Edited by user Wednesday, 20 January 2021 11:25:01 AM(UTC)  | Reason: Not specified

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If we all had the same (good) taste, who would buy all the Fords?
supercoach24 Offline
#3 Posted : Wednesday, 20 January 2021 2:46:46 PM(UTC)
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Thanks for that info HK1837, excuse my ignorance but what is a ZA Carby?

I have found hume have a 4MV carby to suit a manual 308 HG. Are you saying I should be going for a later carby?

was thinking I shoud be looking for Q-Jet with either 7029283 or 7043283.

I am wanting to run my auto choke pipes from the exhaust manifolds as per my normal WW Stromberg Carby. Or are you saying there is a better way?

I have found a valley cover which is correct for HT HG 308, has Holden number 2823087.

I recently rebuilt my 253 to 253 specs and only put in a slightly large, Crane Cam 244521. So I am not wanting to redo the whole engine again, just change the top part to get more air into the engine through the 4BBL.

Edited by user Wednesday, 20 January 2021 3:20:00 PM(UTC)  | Reason: Not specified

HK1837 Offline
#4 Posted : Wednesday, 20 January 2021 3:57:58 PM(UTC)
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ZA is the carby code, but not all have that code stamped on them. ZB is 308 auto, ZC is 350 manual and ZD is 308 auto. Then into HQ ZE is 308 manual, ZF is 308 auto.

The number is 7029281.

7029283 is for a 350, one of those will cost you over $5000.

7043283 is an ADR27 carby for a 9/73-12/74 308 manual.

You have to use a manual carby, or a post 12/74 carby that has a ported vacuum port on it, you don’t want full vacuum for a manual or it’ll race at idle due to vacuum advance getting pulled on. After 12/74 the carbs are the same for manual and auto as all cars needed a ported vacuum port for canister operation.

You can still use the pipes through the exhaust manifold, but the HX onwards Quadrajets have the choke operator on the side of the carby rather than on the manifold with a lever to the carby. So if you get a blue 4.2 carby and put it on your inlet you can run the choke heat pipe straight to the carby, or buy an electric choke conversion for it.

Example Quadrajet. Won’t need mods to work properly on a 253.
https://www.ebay.com.au/...695b9:g:o~AAAOSwyrlcibQi

Edited by user Wednesday, 20 January 2021 9:04:30 PM(UTC)  | Reason: Not specified

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If we all had the same (good) taste, who would buy all the Fords?
HK1837 Offline
#5 Posted : Wednesday, 20 January 2021 8:54:58 PM(UTC)
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I should also add that the later carbs are designed for cable throttle so it may be problematic getting one to work with a HT linkage. It would be best to see if you can get one rebuilt using a HT-HQ primary shaft if that is possible. You could possibly replicate the blue 4.2 carby tune in an older HT/HG 702 or a HQ 704 carb. Problem is finding a manual one, they are prized by 308 manual GTS owners, and once you get into the ADR27 carbs, 7043283 are wanted by SLR5000 and L34 owners, plus HQ and early HJ 308/5.0 Sandman and GTS owners. If you are going to the trouble of building one up to a 253 tune what might work and look almost right is the HJ 5.0L carb 7045281. These are common carbs, every post 12/74 HJ 5.0L and LH to 5/76 LX 5.0L had one. They look identical to the HT-HQ carbs except they don’t have the little tin plate cover at the front, see the one in the link. That cover is the vent point for the fuel bowl but ADR27 carbs have a sealed fuel bowl and vent internally. The throttle operation plate looks a little different as they suit cable throttle but you’ll pick up a HQ auto carb (7041282 ZF) really cheap for its primary shaft. The front vacuum port in the normal spot on the 7045281 is for a manual’s dizzy ported vacuum advance (and to operate the carbon canister). The other port out the back is full vacuum port for an auto, it gets blocked on a manual.
https://www.ebay.com.au/...by-7045281-/154156718746

Edited by user Wednesday, 20 January 2021 9:03:44 PM(UTC)  | Reason: Not specified

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If we all had the same (good) taste, who would buy all the Fords?
kevrev Offline
#6 Posted : Saturday, 23 January 2021 11:45:22 AM(UTC)
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The return line from the carby back to the fuel tank is only installed on cars with A/C.
My old HT Brougham with factory A/C had the return line fitted, with a different fuel sender which had the return line fitting as well as the fuel outlet.
I have a 29282 ZB carby off an auto 308 HT in the shed, let me know if you want a photo of it.
Cheers Kev
HK1837 Offline
#7 Posted : Saturday, 23 January 2021 3:05:08 PM(UTC)
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Originally Posted by: kevrev Go to Quoted Post
The return line from the carby back to the fuel tank is only installed on cars with A/C.
My old HT Brougham with factory A/C had the return line fitted, with a different fuel sender which had the return line fitting as well as the fuel outlet.
I have a 29282 ZB carby off an auto 308 HT in the shed, let me know if you want a photo of it.
Cheers Kev


Those are the easiest HT-HG 308/350 carbs to find, it is almost certainly off a Brougham. Around the time 308 was made available outside Brougham they started putting the 70 back on the front. Sometimes they don't have the ZB either, just the number. The earliest I have seen is 0159 on a ZB.

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If we all had the same (good) taste, who would buy all the Fords?
kevrev Offline
#8 Posted : Saturday, 23 January 2021 8:19:08 PM(UTC)
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The carby I have is dated 1969, it's the second one I've seen with that date.
Rochester must have made them in batches, I've seen quite a few Manual HT 350's with carbies with an 0719 date for example.
I'll check my mates 29281 ZA carby date when I'm over at his place next, he has a November 69 built manual 308 GTS Monaro
HK1837 Offline
#9 Posted : Saturday, 23 January 2021 9:18:18 PM(UTC)
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They are in batches, all of them. Even the really common carbs like the pre ADR27 HQ auto and HJ carbs. I think there is only 4 dates for HT-HG 350 manuals, that I am aware of anyway, plus the first ones with HK carbs with no date. The last of those 4 is HG only so that leaves only 3 covering HT. That is normal process though, there are large amounts of everything sharing the same cast or completion dates given the economies of scale involved and the fact that (ignoring public holidays) 2/7 (near 30%) of the days in a year are not workdays for some GM divisions.

Edited by user Saturday, 23 January 2021 9:19:15 PM(UTC)  | Reason: Not specified

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If we all had the same (good) taste, who would buy all the Fords?
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