Progressing ever slowly on my historic rally car build.

I am going to use twin HS4 (1.5" /38mm)(yes know can do better with a single etc etc) but this is what I am doing..

The carbies I bought off ebay and came on an AEG573 manifold - which as far as I could make out where mainly for twin HS2. This looks standard (?).
Rather than go to the hassle of modifying thought I get a repro C-AEG489 (12G2464) manifold which were for the HS4/HS6... which has now arrived.
This comes pre-modified aka Vizard.

What surprises me however is the manifold to head port sizes.

The is not much between them on the Carby mounting side - both pretty much around the 38mm mark.
On the head side the 573 is around 34-35mm.
The 489 is only 30mm !

To compound the issue - the head ( a Mk1 AEG163) is heavily ported old school ... and inlets opened up to around the 38mm mark.

Question:
Should I open up the ports on the 489 - and to what size ? (and only has about 6mm of wall at the bottom flange)
or
Work on the 573 ? (this has about 5mm, as well as being more open to start with... )

(There is option 3 there an already ported original 12G2464 manifold that came with the head when I bought it 20 years ago - and currently on another car... but want that for another project...)






Other questions while I am at it...
The Carbs came with #7 needles...
It's +30 bore - so right on the 1300cc and will be running an RE13 and Maniflow LM4 extractors to 1 7/8" exhaust (maniflow) ....
Any thoughts if these are a good starting point needle - or likely to be way off with this combo ??

(and this all started by buying a roof rack !)


ps Anyone have any idea who MM or MLM might be ? (presume they were the ones who ported the head originally... bought it from a bloke in Sydney with a dismantled GT abut 20 years ago)

I would get a bigbore manifold gasket, open the manifold up to 36-37mm dia if there's 2 or 3mm of flange left there to seal on.
You will need to dowel the manifold to align it, or else weld alloy on the flange ends and machine it so that it can locate on the studs.

I had a 1293 with a Wade cam, twin HS4s and it ran sweet with #6 needles, they worked fine on another 1275 with RE13 cam also.
A #6 is close to a #7 so you should be in the ballpark for starters.
#7 is a bit richer, put both into http://www.mintylamb.co.uk/suneedle/ and you'll see.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I little bit of trivia that may be of use.

You may be aware that Cooper S's built for NSW Police to SPO41 had HS4's on a modified AEG573 manifold. Did the carby set you bought on eBay have specification tags on the float bowls? If genuine SPO41 they would be AUD488 which was designed specifically for NSW Police by SU (Bill Bressington did the design work).

The inlet manifold modifications included relocating the mounting studs from vertical to diagonal to suit the HS4's, Aralditing a grub screw in the old top hole as it penetrated the chamber and enlarging the ports. If your manifold is genuine SPO41 it should have a 3/8" Whitworth x 1.00" socket headed grub screw in the top hole. The two screws on yours coming down from the top that presumably are there to lock whatever is sealing the holes is not part of the specification. The rework is documented on drawing AYG0245 (MK II S) and AYG0280 (Clubman GT) and I believe was done by Lynx Engineering at the time.

The AUD488 specification included 30 degree adapters to get the HS4 float bowls vertical. The original specification was for CP4 needles and blue springs, but I've heard that other combinations were used in practice.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Thanks for the replies and advice ... just what I wanted.... puts me more at ease before I jumped in
Will try my hand at modifying the new manifold....
Just surprised the new one was so "restricted"... and wondering if changes in modern thinking or just strange design.

Will check the details on the carbies (but think no tabs)..
and also those I already have - they were supposedly off a police GT - which I dismissed at the time - but a number of other things about that GT make me wonder now I know more...
(Doug - I was already planning on collecting all the odd things and contacting you for your input/help about it... but that's the next project ... )

Forgot to mention, the AUD488 HS4's will both have a brass breather tube on the body to accommodate CCV (Carburettor Crankcase Ventilation). Rubber breather tubes connect to a plastic Y piece, and then to the rear cover oil separator. SPO41 specified CCV in place of the usual PCV. Let me know if you want a picture of this setup.

And they had Lynx Ramflo air cleaners.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43