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

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/...?hash=item28a2b695b9:g:o~AAAOSwyrlcibQi

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

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

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

I have a 7029283
As we know these are stamped
29283
Date code 0159

They look identical to HQ but have the heater hose boss drilled and tapped. Not sure if they are the same cast number, will look.