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MG Midget and Sprite Technical - Benefits of single 1'3/4 SU

Are there any benefits of having a single 1"3/4 over the twin HSU2's or even over a single Weber.

Thanks for looking Wayne.
W Williams

No requirement to "balance" a pair of carbs

More efficient than the weber

Easier to fit

If you compete in autotests at all, the 1"3/4 (and HS2/4's) will not suffer from fuel starvation the way the weber will when changing direction quickly.


But nothing beats the sound and look of a 45 weber

Or does it.....

Just bought a pair of 45 dellortos!
That is one to replace my 40 weber and one......
I might just go for a twin single barrel setup ;p
Onno Könemann

Are there any benefits for road cars
W Williams

Wayne. I have an SU HIF44 on my mk3 Sprite road car and I find it smoother, more powerful and altogether a better driving experience. And as Peter says, no more balancing twins.

b higginson

Hi Bernie,
would you be so kind to contact me via email.

Cheers Wayne.
W Williams


I have a single SU HIF6 (1 3/4") with MG Metro airbox + K&N filter on my 1380 and in a back to back rolling road test with a 45DCOE a few years ago through this BBS, the Weber with full radius trumpets and K&N filter gave 4 bhp more than the SU - 106 vs 102.

A couple of years later on the same rolling road, and with a slightly higher CR and after removing the MG Metro air box with K&N filter inside, it produced 112 bhp, but I did not try the Weber that time.

Driving, the SU is very much nicer at slowish speeds, and especially picking from low revs, whereas the Weber would do very little until 2,000ish rpm.

The Weber sounded great, but not for long trips, so have not refitted it since.

Richard Wale

Somewhere in the depths I have a copy from an old magazine that did back to back tests with HIF44 on a midget. The HIF provided more power and improved economy over the standard twins.
M H Allen

This should in part be better with the dellorto as they atomize the fuel finer than a weber.
Though I should reread vizard to be sure.

No benifit on a road car to use a twin single barel setup.
I was only kidding
I seem to be collecting carbs now though
Twin hs2
Weber 40
2* dellorto 45
Hiff 44

Need more cars to fit them to!
Onno Könemann

I hung on to my twin SUs for ages, partly because I liked the methodical challenge of getting them set up right, but mainly 'cos I just liked the look of the things! but eventually I changed to a single HIF 44. And it is definitely better! The most significant thing was the improoved economy. With no other changes it increased from an overall 32 to 38mpg. On longer trips, rather than my regular nipping in to town journeys, I can easily get 42+ mpg. And I don't dawdle!

Like Guy, I'm not renowned for hanging about

And on a decent motorway run (such as London next month for the Ace Cafe Classic Cars meeting) I can get there and back from Brum on a tankful---just!

Although I'm running on fumes by then, ish!

The journey may well have several sections at "oops I missed the speedo reading" velocities

I love my HIF44

(love that run home up the darkened M40 too, sheer self indulgence)

Bill 1

"This should in part be better with the dellorto as they atomize the fuel finer than a weber.
Though I should reread vizard to be sure."

They do atomize the fuel better than the Weber which is why I tend to use them on my race engines.

HOWEVER, Vizard states that the A-Series doesn't like finely atomized fuel so he claims the Weber is better here for ultimate power, the Dellorto being better for economy.

I haven't done back to back tests on an A-series to prove it, I just bolted a 45 Weber on the racer. :)

Personally i prefer Dellortos, they have a better jet range and they don't have those bloody stupid internal throttle return springs that have a nasty habit of coming adrift and flying down the inlet tract (with predictable results!).
Deborah Evans

Thanks for looking it up for me!
Same bark
Same acceleration
Same look
More economy
sounds like a plan!
Onno Könemann

Hi Wayne, another thumbs up for the HIF44. So easy to set up and seems to give more low down torque than the twins.

Mark Whitmore

all we need now is for someone to manufacture an inlet manifold for Midgets so that the HIF44 will sit low enough to clear the bonnet without having to modify the dashpot

The minispares inlet is very good (is it true it is only a copy of the Metro inlet, cast in aluminum?), but angled "up" for the mini, creating the clearance concern.

Didn't Maniflow make a Midget one in steel?

Norm Kerr

For a very short time I had a Solex twin choke carb on the car. It looked a bit like a Weber 40 DCOE, I can't remember the number of it. The car absolutely flew, but the induction noise was horrendous so I put it on Ebay and used the money I got to buy my HIF44. I was very lucky to pick up a MiniSport shallow angle manifold which I had my local machine shop to put a slight chamfer on the head mating face to get the required bonnet clearance. See pic (I did trim the cables by the way.LOL.)

b higginson


Yes, Maniflow produce a Spridget friendly [ie 20 deg] steel inlet and I have one awaiting installation.



Doug Plumb

Thank you everybody,excellent response as usual,which fetches me to my next question.
Has anybody got one of these manifolds tucked away somewhere that would be for sale.

W Williams

On my Turbo I run the HIf44 with a fuel regulator as the unwanted fuel is sent back to the tank via a return pipe, I would like to know if folks are getting good results with this carb without the regulator ?
Rob Newt

Rob, there are tons of minis running around with 1275 engines and HIF44 single carbs, with no regulator, and no return pipe.

If I understand your question correctly, I'd say that the key to not needing a regulator is having a fuel pump that delivers 3 ~ 4 psi. But having a turbo your application might be quite unique, compared to the usual 1275.

Norm Kerr

What do you mean Rob

Why do you ask such a strange question?
Robert (Bob) Midget Turbo

<Why do you ask such a strange question?>
I have heard conflicting storys that a HIF44 single carb needs a fuel regulator and some dont, I realise that a turbo needs a regulator but was wondering if any one has had to fit a regulator to a na car because of over fueling using the HIF44.
The reason I ask is I have just fitted a standard 1275 engine into my A35 and I just happen to have a spare HIF44 lying around from a turbo.
Keep it hush hush about the A35, I know this is a Midget forum !
Rob Newt

Hi Rob, I thought there subtle differences between the turbo and N/A carb (seals)?

Would it be suitable?

I don't run a regulator and don't have any overfuelling issues.

Mark Whitmore

As far as I am aware you can use a turbo HIF44 on a na car but not the other way round, the turbo HIF44 is a sealed system, so a normal HIF44 would leak fuel under pressure.
Thats if anyone can tell me different?

Mark have you sorted your brakes, I have a spare backplate if you get stuck.
Rob Newt

There should be no reason to need a fuel reg on an n/a car with an hif44 provided the fuel pump delivers the correct pressure.

Hi Rob, will be having a look today so will let you know (its the drivers side that may be at fault)

Mark Whitmore

Rob, you have mail

Mark Whitmore

Hi Rob,

Could you email me please as I have a couple of questions for you and I cannot find your email address.

W Williams

You certainly don't need a reulator using a turbo HIF.
Cheers John

surely in turbo application you need a rising-rate regulator to maintain fuel pressure at 4 psi above boost pressure, as fitted on Maestro and Montego turbos? thought Metro turbo uses same parts??
David Smith

It does David and from this statement Rob knows that too
""I realise that a turbo needs a regulator but was wondering if any one has had to fit a regulator to a na car because of over fueling using the HIF44.""

Robert (Bob) Midget Turbo

I presume the single 1 3/4" is for the 1275.
Is it possible to do the same conversion on the 1500 engine ?
Less hassle to set up than twin Su's.
S Langston

Dave, I was meaning you don't need a reg if you are just using a turbo carb alone, not with the turbo.
Cheers John

Priced an inlet manifold from Maniflo>> £130 plus vat and postage!! Crazy, and they're not even stainless!!!!!!!
Titan said they could do them beween £60-£90 each with a minimum batch of 20. Worth a thought.
Cheers John

"Is it possible to do the same conversion on the 1500 engine?"

It is but why you would want to is beyond me because you will effectively be choking down!

To do it you need to source a single SU manifold from a Herald 13/60, Triumph 1300 FWD or early Triumph 1500 RWD/Toledo ie NOT 1500TC or Dolomite.

Then you need to make up an adapter plate.
Deborah Evans

Try Mini spares or David Manners Birmingham, my brother has just ordered one for his Midge....£35,not sure of the make though but they say it has the clearance for a Midge.

Btw Turbo HIF44 fitted to my A35 today, and it runs a treat with no issues, NO regulator.
Rob Newt

There's a Titan manifold for a Spridget on ebay at the moment for about £100.00 so getting Titan to do a batch would be worth their while I would have thought.
Gary & Gaps

Intestingly Titan told me that they supply Mini Spares. Not sure if the one MS are presently selling is the same as the Titan. At £35 it would be a good price.
Cheers John

John. I went into this with Titan about 18 months ago and they came up with the same figures. I gathered a load of names of interested parties on here, but when they heard the price I got a 50% drop out, so I bagged it and sorted myself out with a MINISPORT manifold which I had to get modified as mentioned above. Titan also told me that they supply Mini Spares, but when I contacted them they said they were all sold and weren't getting any more from Titan.
As Gary says, if Titan had their finger on the pulse they could do some good business, but they just seem to be dithering. I'm sure if they made a batch they would be able to sell them, they may not fly off the shelf, but they would get rid of them if the price was a bit more reasonable.

b higginson

How difficult would it be to modify the moulds for the normal mini manifold to put more meat on the manifold mounting flange - then they could simply be machined to the shallower angle suitable for midgets?

Sounds simple to me!

I just remembered that if you fit an HIF44 to an A series car you will have to get the 1500 type throttle pedal as the organ type pedal fitted to A series cars doesn't open the throttle wide enough to get the butterfly horizontal, so you will never get to full throttle. Also, even after I had fitted the later pedal, the throttle was still not quite making it all the way to the stop. I looked inside the car and found the answer. The thickness of the carpet plus underlay was preventing the pedal from going all the way down, so I cut a section of underlay out and now it works fine.

b higginson

Good point Bernie

Hi Bernie, I modified a throttle linkage from a different carb (bent it!) and I get approx 98% travel with an organ pedal on a HIF44.

Mark Whitmore

You never know when you might just need that extra 2% though

On my 73 I removed the organ pedal and replaced it with a bolt on foot plate, kept the rest of the linkage original plus a new cable to suit the HIF carb.
No need to change to a 1500 pedal, IMO it appears to be identical except for the organ pedal part.
Ian Webb '73 GAN5

I have the HIF 44 and Titan manifold (bought from APT but at last check, they no longer carry them). The reason I called APT (after using the setup some 3 years) was that the water heating pipe (cast into the manifold) was starting to leak coolant into the inlet tract (showing up as rust on the plugs).

I had to bypass the water pipe and seal it off. I always wondered how they could cast aluminum around a steel pipe without suffering fractures due to differing expansion rates. If I had it to do over, I would have gone the Maniflow route. The blanked off pipe is useless, ugly, and takes up room.

JM Morris

you should have never connected the pipe ;)
It is meant as an economy measure (heating up the manifold) and a way to prevent carb icing in the winter.

it is as you say useless, ugly and robs power!
Onno Könemann

If it's any use, oCoop are selling a manifold for the mini at £35-85 which it may be possible to modify.
Graham P 1330 Frogeye

I adapted my HIF44 throttle linkage (Its a standard crank rather than progressive snail) so std 1275 pedal gives full throttle.

Echo the general trend of high 30's consumption even driven hard (1275 or 1380 Engine) over low 30s of the twins with similar driving. (Enough that friends noticed the extra range the year I changed for Le Mans!)
(URL is for HIF44 pics despite appearances)
Dean Smith ('73 RWA)

Hi Dean,

some great informative pictures there,especially for someone like myself
who is just starting out.

W Williams

This thread was discussed between 28/05/2011 and 05/06/2011

MG Midget and Sprite Technical index

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