MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - What Single SU, MANIFOLD fits under a Spridget Hoo

I am looking for a single SU carb Manifold that will fit under a bugeye Sprite Hood ( Bonnet ).

What makes / brands fit ?

Do you know who sell one , ( and if more than one model ) part number ?

Do you have one ?
Kazan Mohrs

The only one I know that fits is branded Titan. Not sure who makes/made them but someone else will know.

When I did my Frogeye I used one made by Howley Racing made in the 1970's mostly for Mini's. It didn't fit as I found out when I shut the bonnet for the first time. I took it to a machining company and had the face wedged (the face that mates with the head) varying from 0 at the top to 2mm at the bottom. This was only just enough and I had to additionally remove a small piece of the part that screws into the carb dashpot.

Others have managed to get some additional clearance by wedging the insulator blocks between carb and manifold.

Some models of car had SU carbs with reduced height. The MGB V8 and Rover 3500 come to mind. I don't know it they will solve the problem though as I personally haven't tried one.

Rob T
Rob aka MG Moneypit

Not all the Titan ones give the clearance needed. They produced their standard one, intended mainly for minis I think. And then they produced one with a slightly reduced angle which gives the clearance for the Spridgets. But they are quite rare I believe and the difference is subtle enough not to be immediately apparent. So beware, if for example buying on Ebay.
GuyW

Contact these guys. I believe that they can make one that fits.

http://www.maniflow.co.uk/index.php?view=product&from=162&product=1192
Martin

I have a Maniflow one as I wanted to fit two HS4 carbs on my frog. The lads at Maniflow knew the dimensions that needed to be achieved and it all went together perfectly!
Bob Beaumont

Hello kazon

in the usa... call minimania and askfor there service tech to talk shop.

They will have exactly what your needing including some very nice titian knock offs

make sure and ask them directly for a midget manifold and not a mini manifold... the 2 manifolds are differsnt by 20 degrees because the mini 1275 sits transverse and the midget sits inline

Id stay with the SU carb over the webber ... unless you can get an orginal webbber and NOT the newer china made webers which from what read and not very compatable to the old webbers and are not to well performing ither

id also recommend the Su HS 4 carb or the SU Hiff (6 ?) Over the SU HS2

if you stay with the SU ... talk shop with minimania about needle selection ... if not them then joe curoto out of NYC... he is the usa top expert on all things SU esp needles

let us know wbat happens


And i almost forgot ask minmania about the plastic insert that adjust the angle of the float chamber ... there like a dollar but you may need to adnust it to keep it 180° vertical with the new set up.


prop
Prop and the Blackhole Midget

Agree totally with Rob's comments regarding the Titan. I think that is the manufacturer and, yes, beware the Mini one as it's doesn't have a suitable angle. They do come up on ebay from time to time.
Have a look in the archives too! This has come up lots of times.
Graeme Williams

When converting to a single SU HIF44 on my Frogeye I bought a Maniflow inlet manifold. It fitted perfectly, and I had no clearance problem. I also used a K and N cone air filter. If you look at their web site you can get a number of options e.g. vacuum take off. There is a definite improvement in both performance and fuel economy over the old 1 1/4 SUs.
Good luck.
Nick
J.N. Williams

I used a Maniflow inlet, together with a deep K&N filter containing a substack, when fitting a HIF 44 on my Midget. I replaced the 'standard' damper [LZX 1505] with the lower profile LZX 1313 to maximise bonnet clearance.

If you engine is 948 or 1098cc, the HIF 38 may be more suitable.


Doug Plumb

I have this manifold for an HIF44 in my attic. I don't know if it is the right angle for a Spridget, but I want to sell it.



Mike Howlett

Picture of other side.


Mike Howlett

I reckon you're right, Doug.

I've got a HIF38 and a Titan that hasn't had its reducing lip ground off yet, and I'm trying to decide whether to go for twin carbs as original, or the HIF. Peter Burgess was inclined to favour the twin set-up. Just.

Easy enough to try both, I guess. The twin carbs have a simple total area of 1285 sq.mm. while the single gives 1134 sq.mm. I suppose there's more butterfly and spindle in the way on the twins.
Nick and Cherry Scoop

I like the twin HS4's on mine. Slark who set them up on their RR said they were marginally stress marginally better than the single but then there is the hassle of tuning them.........You pays your money etc etc
Bob Beaumont

Nick,

The twin carbs may have a total area of 1285 sq. mm. but you only get 642.5 sq. mm. per cylinder whereas with the single you get 1134 sq. mm. per cylinder. That means that you would get more flow with the single. Or am I missing something?
Martin

I think you must be right, Martin. That seems an awful lot of extra flow for a 948cc engine.

I'm sure somebody here has said that engines can be over-carburettored. What happens when that mistake is made?
Nick and Cherry Scoop

Fuel entering the engine, on a microscopic level is approximately 14.7 parts air & 1 part petrol. As intake & carburetor cross section increase velocity will decrease. Since air & fuel have different densities, if the velocity decreases to a certain point the atomized fuel will settle out & the fuel mixture will become inconsistent and performance & mileage will suffer. This is one case where bigger is not necessarily better.
s1

Thank you - that's very clear.

I guess 1⅛" was reckoned to be right for the 948 engine, but perhaps after PB has opened the head up a bit, it might like a bit more.
Nick and Cherry Scoop

. . . . do you think HIF38 might be too much?
Nick and Cherry Scoop

An HIF38 is a 1 1/2" bore, it has a smaller throat diameter than 2 of the 1 1/8" SUs but you can improve flow by removing the jet bridge and leaving only the jet nut sticking up.
s1

Hi

Ive got a HIF44 fitted on rwa 74 midget. works well, fitted by alex on 07540 551173 (surrey area), I think the manifold is a titan, but will check when I get home.
B Burrowes

Martin,

would you mind explaining your calculations - I can't get my head around them, mind you my mathematics peaked at age 16 - a long time ago!
Thanks

Jeremy
J Tickle

Jeremy,

>The twin carbs have a simple total area of 1285 sq.mm. while the single gives 1134 sq.mm<

I read that as saying that two carbs have 1285 sq. mm of area meaning that one carb has 642.5 sq. mm. Each cylinder gets that amount of flow since there are two cylinders per carb whereas with the single carb with 1134 sq. mm each cylinder gets 1134 sq.mm since each cylinder is fed by that one carb.
Martin

Thanks for the clarification Martin, I was struggling to comprehend how the bigger number actually meant less flow in practice as I'd simply divided both figures by 4 to determine how much flow each cylinder received.
J Tickle

I don't think it's as simple as that. On the twin SU inlet there is a balance tube so that all cylinders see both carbs.

The cylinders fire 1,3,4,2,1,3,4,2 so ignoring the first cylinder we get 3,4 through rear carb and 2,1, through front carb for each engine revolution. However, because of the cross tube when 3 and 4 are intaking both carbs are supplying air/fuel. The same when 1,2 are intaking.

Something to do with inertia and momentum of the air/fuel mixture.

I suppose if there was no cross tube you would get 3,4,nothing,nothing through the rear carb per engine rev. The nothing,nothing will allow the air/fuel to stop, then the 3,4 would have to accelerate the air/fuel again. A constant flow of air/fuel would be the ideal which I suppose is the job of the cross tube.

A tricky subject!!

Rob
Rob aka MG Moneypit

Rob,

I was just doing the simple math not knowing how much of an effect the balancing tube has on the whole process. As you say, a tricky subject. And one that I'm not qualified to explore.
Martin

My instinct is to think that the balance tube doesn't really pick up much mixture flow from the further carb, but prevents piston flutter by maintaining suction.

I'm with you, Martin: waiting for an expert to come along.

But it seems clear that a HIF38 on a Titan will give each cylinder its undivided attention - so, do you think that would be overcarbing a 948?
Nick and Cherry Scoop

As the HIF38 was fitted to the 1000cc Austin Allegro [and the same size HS4 was fitted to the 1000cc Mini], I would think its fine for a 948cc Sprite.
Doug Plumb

Thanks Doug. In that case, I'll get it out from that dusty corner and start dismantling it.

Needle, anyone?
Nick and Cherry Scoop

Nick,

From the SU Reference Manual for a 1981-2 1000cc Austin Allegro:

standard needle NZX4014ADP
spring AUD4355
damper LZX1505
jet WZX1455

I guess the 80's was the early days of emission controls hence no weak or rich needle options listed to discourage 'tweaking'.

HTH
Doug Plumb

Thanks very much, Doug. Have you actually got these manuals?

I see from the Mini forums (fora?) that AAU is favoured.
Nick and Cherry Scoop

Yes


Doug Plumb

Nick.
Forums vs fora. I used to wonder about this so I did some digging and found that either is correct although 'forums' tends to be more widely used outside scientific and scholarly circles.
graeme jackson

So 'forums' would be right on the money for Mini enthusiasts, then.

But, what of us?
Nick and Cherry Scoop

we use the alternative olde english form "BBS"
Dean Smith ('73 RWA)

This thread was discussed between 01/10/2016 and 19/10/2016

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.