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MG Midget and Sprite Technical - identifying & upgrading my SU carbs

Hi, My 1500 midget certainly has SU carburetors. I know that much. But how do I identify exactly which sort they are? I've googled some original specs for the date of the car (it's 'P' reg) and they can't agree.

I'll be getting the engine rebuilt this year and expect that bigger carbs would be in order. I don't want the expense of fitting Webers (I'm still short a pair for another project). SUs seem to be cheaper, and are reputedly a torquier option. That seems to suit the type of engine I'm after.

Thanks, Tim

t halket

should be a small metal tag on one of the screws holding the float chamber lids on, with an SU number probably AUD665
David Smith

David, Just got back from a suprisingly cold garage.

The number is AUD665R. But could only find it on the rearmost one. Safe to assume they are a matched pair.


t halket

yes suffix is R for rear, F for front. All info from Burlen website...
David Smith

most likely hs4's. very good carbs. Vizards A series tuning book (aimed at minis, but very useful) shows different ways to improve the airflow of hs carbs (and others). it covers making changes to the carb mouth, carb piston....ets, air filters and ram pipes! very good read.

from the book twin HS4s can handle up to 97HP engine and can supply 166CFM.
Rich K

there's no doubt, they are HS4s - like I said it's all on the Burlen website
David Smith

97bhp. That'll do.

I'm hoping to discuss engines with Deborah Evans soon. Looks like a taget to me.

Thanks everyone, Tim
t halket

If you don't mind original looks, I've always gotten on with the later HIF's better than the HS range. They also seem to be more widely available. I had something like a dozen knocking about at one stage as my local scrappy had a load of meastros, montegos and metros in, so I had the lot as things to play about with.
S Overy

Im not sure they make an offical duel HS6 carb set up 1.75"

According to das hammil... the duel HS4 is great for 1000 to 1800cc engine with a BHp output of 65 to 115 Hp

Well okay Im a bit wrong ... there is a duel HS6 but looks fairly rare it was used on a 1972 marina 1750 TC in austrial... the engine is a really big 4 clyinder 1748cc code numer ...AUD 504 (F.R.)

several for triumph... austrila

fzx 1105
fzx 1117

USA .... MGC has them

AUD 150
AUD 341
AUD 287
AUD 342...But these USa MGC versions are 6 cly and in the 3000cc range


Do you mean they didn't do twin HS6 for Spridgets?

The twin HS6 package was common on old Volvos with the B-18 and B-20 engines. I can't give you an exact year range, but approx late 50s to late 60s. Come to think of it, didn't the TR3 and TR4 use them until they went to the Strombergs? And, I think thatís what the big Healey used too.

C R Huff

I don't think so charlie looks like only the hs 4 . on the tr3 I'm thinking you're right according to the manual by das hammiel

I think a duel hs 6 is just too big for 15 to 1600 my opinion
1 Paper

This thread was discussed on 20/01/2011

MG Midget and Sprite Technical index

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