1 3/4 SU ?

Standard & electronic conversions

1 3/4 SU ?

Postby iank » Sun Feb 21, 2016 7:13 am

Got given a carb today, the size of the outlet is 1 3/4, so i am assuming this is how you measure it :?: . Sadly it did not have a tag on it, so i cannot accurately identify it. No joy looking on the SU carb site either. From what i can gather from the Vizard book, it seems to be an HS 6. Can anyone enlighten me as to if it is, or is it a HIF 6 ?. The only numbers i can find are AUD 8490, AUD 920, on the main body, and AUC 1310 PDCH on the float bowl. I am wondering if there is any advantage using this or staying with the HS 4 currently in use. Engine is a standard 1300 Marina with a Mini sport intake and Maniflow exhaust.
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Re: 1 3/4 SU ?

Postby frosty » Sun Feb 21, 2016 7:22 am

.... everything I don't know is here ... lol :raz:

http://www.sw-em.com/su_carbs.htm

plenty od info out there Ian
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Re: 1 3/4 SU ?

Postby Custard » Sun Feb 21, 2016 9:55 am

Would be easier with a pic.

On the HS's the number matched the 8ths of an inch above the first inch.

HS6 would be 1 inch and 6 8ths which is 3/4.

If it is a separate float bowl on the side then it is the HS whereas the HIF is Horizontal Integral Float but the HIFs then started using metric measurements so an equivalent to a 1 and 3/4 would be a HIF44 with the HIF 38 being the 1 1/2 equivalent.

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Re: 1 3/4 SU ?

Postby Custard » Sun Feb 21, 2016 10:01 am

http://sucarb.co.uk/float-chambers-spar ... -type.html

AUC 1310 means it is an HS type float bowl so it looks like you have a HS6

Sean.

Compare yours to pics on this page.

http://sucarb.co.uk/technical/
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Re: 1 3/4 SU ?

Postby bmcecosse » Sun Feb 21, 2016 7:15 pm

As above -an HS6 - perfectly good carb - but no advantage on your standard engine. You would need big valve 'ported' head, cam upgrade - and all the other work necessary to allow higher revs to be used safely.
 









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Re: 1 3/4 SU ?

Postby iank » Mon Feb 22, 2016 7:15 am

Thanks Chaps, that has answered the question :) . Defo a HS model then Sean as the bowl is seperate, just never seen an HIF one.Might just keep it in case the lotto fairy pays a visit ;) .
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Re: 1 3/4 SU ?

Postby MM » Mon Feb 22, 2016 7:13 pm

Nowt wrong per se with using a 1 3/4" SU on a 1275cc A-series; after all, the late '80s/early '90s Maestro 1.3s, Metros, etc. had a HIF44 as standard; I fitted an ex-Maestro 1.3 HIF44 (albeit with MG Metro needle) carb to my standard 1275cc MG Midget engine and it's been excellent - easy starting, smooth running, good power and torque, and respectable fuel economy.
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Re: 1 3/4 SU ?

Postby geezer » Mon Apr 18, 2016 4:39 pm

Good find. I say go for it.

I have twin HS2 carbs on my Morris. Runs fine. A Single HS6 has the same, or close, throttle plate surface area as 2 HS2 carbs. I would think it would be fine.

Since the throttle shafts and bodies are warn out on my twin HS2s I'm thinking about converting to a single HIF44. The HIF44 conversion is actually cheaper than sending my 2) HS2s off for a rebuild.

I would do an HS6 if I could find one in good condition.
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Re: 1 3/4 SU ?

Postby bmcecosse » Mon Apr 18, 2016 8:56 pm

Errrr - you forget that with twin carbs - each cylinder only feeds from ONE carburettor - there is no 'cross flow' on the balance pipe - indeed the balance piep spoils the air flow into the ports! So even a single 1.5" carb (on a good manifold) will beat the tiny twins. Putting a 1.75" carb on is fine - but consider first how often you actually run 'foot to the floor' with the 1.5" carb - before bothering to make the change to the larger carb. Because that's all it does - gives more 'full bore' air flow = power. If it has a separate float, it's not an 'HIF' = Horizontal Integral Float..... Perfectly good carb, although the HIF is designed to eliminate 'surge' on cornering, but you must make sure the float is vertical - and it should be on the radiator side of the carb, so that under acceleration fuel is pushed into the jet rather than away from it by the fierce (!) acceleration... Without the head/cam etc mods - it's really not worth the hassle.
 









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