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MG Midget and Sprite Technical - which su carb do i use

Hi there i have a 1293 cc midget with a mild steel lcb with a maniflow single box system a titan motorsport inlet standard cam shaft normal unleaded 1275 head and electronic ignition.i have either a hif38 or a hif44 carb to fit whats the best one to use and what needle should i start off with.
mm morgan

I (and lots of others) used the HIF44 and found it gives good torque and excellent fuel economy too. The most commonly used needle seems to be BDL, although I used a BBW with success. Actually looking at the profile of the two types, the BDL and BBW are very similar.
Mike Howlett

I would not go duel HS4...bigger is not.better

ither stay with rhe duel HS2 or the single.HS4/HIF 44

the smaller the dia.of.the carb throat.the faster and more forceful.the fuel charge will flow into the cly head

there is a SU windows based computer app you can down load...you simple fill in the info...and.it.will.tell you what.needle you.need...its a fun program, id consider.it more of.a suggestion / starting spot then an absolute fact for which to.find the best needle spec

prop
Prop and the Blackhole Midget

I had good results with twin 1 1/2 carbs from an MGB. However if you've already got the titan single carb manifold then single HIF44.
Rob Armstrong

Ok rob cheers for that
mm morgan

On Metros the HIF38 was used on the smaller capacity 1 litre engines and the HIF44 on the '1300's and since the 1300 Metros gave both good performance as well as good fuel consumption on them, it's a no brainer.

My HIF runs a Peter Burgess modified BDL needle and gives me excellent power (read speed!) and consumption on my Titan manifold.

I run my heater pipe through the Titan's built in pipe.

Bill1

Mmmm there are books with this stuff in...

Prop - the HS4 is an an imperial inch and a half while the HIF44 is a metric 44mm or and inch and three quarters. Pre metric HIF inch and three quarters were known as the HIF6 which makes sense given it was the same size as the HS6.

I think Bill has given the clearest answer in the absence of ready supply of HIF7s with an HIF8 arguably being too big (and also scarce).
D Stapleton

hi bill what sort of economy are you getting and my inlet is also water cooled the same as yours.
mm morgan

My 1275 in a mild state of tune can regularly achieve 44 mpg with the singe HIF44 carb on a BBW needle.
Mike Howlett

My car when in standard tune with a 4.2 diff did 45mpg on a gentle long run on the Hif44.

Even in a fairly high state of tune and a 4.5 diff it managed 37mpg on the motorway at 60-65 which was suprising.
John Payne

That fuel consumption sounds good, what should I expect from a standard 1275 with the twin carbs?

Carl
C Bintcliffe

I used to get 45mpg on a long fast run with the bigger carbs and mg metro head.
Rob Armstrong

hi john payne what air filter did or are you useing and what weight oil do you put in your dash spot.
mm morgan

>>>>>>That fuel consumption sounds good, what should I expect from a standard 1275 with the twin carbs?<<<<<

Carl,

it really depends on if you knife blade the butterflys or not

if you paint the motor fire engine red and knife the butterflys...id say at least 10-12 extra HP and an additional 8 mpg

prop
Prop and the Blackhole Midget

Filter is a K&N pancake (see profile pic) and I use whatever I put in the engine in the dashpot.

To be honest I didn't really do any MPG runs on the twins but it was definitely better when changed to the HIF, smoother and better revving. Having read into it a bit more in the ten years since I converted it I'm sure the twins were worn out and needed a rebuild though.

Cheers Prop, I knew that black paint was holding me back!
John Payne

I use a big red ITG foam filter from Kim at Magic Midget, and like John I put 20-50 engine oil in the dashpot. Note the little piece of high tech padding, stuck on to stop the filter chafing the bonnet lid!



Mike Howlett

lovely engine bay john really nice,do you have a stub stack fitted or not.
mm morgan

Carl,
there's a lot more to mpg than carbs but to give you an idea look at the road test reports from back in the day and if your whole car is in good condition and fully serviced, maintained, repaired and driven frequently then you should get better than those figures but it does depend on the nut behind the wheel

on my old not very good twin carbs on my mildly tuned car I got 50 mpg at constant 50mph (when driving 100m on M6) - I would expect to get more now my whole car has improved but I enjoy the driving too much to have checked

. and thumbs up from me for the K&N and continued use of the original plastic vented/filter oil filler cap for better breathing rather than the chrome ones
Nigel Atkins

Cheers Mr Morgan. There is a Pipercross style stub stack in the filter but I intend changing it for one of the solid ally ones from MED or similar.
John Payne

cant remember what manifold i have, but i had the clearance issue with the bonnet. . .so at the minute the carb/manifold is on the to do list !
p bentley

This thread was discussed between 09/01/2013 and 14/01/2013

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