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MG Midget and Sprite Technical - SU carb HIF44 conversion

Chaps

Further to a more detailed examination of my twin SU carbs on my modded head 1275 73 RWA, I find I have (according to the tags on the float chambers) an AUC 509F – from a Bentley or RR apparently - and an AUC 700 – from a 2 litre AC apparently! They seem to work well enough, having spent ages balancing, adjusting mixtures, and generally fettling them as much as practically possible, but I do feel that I am flogging a dead horse for further improvements. In addition, I have no viable fast idle mechanism when on choke, which is a bit of a pain. All of this inherited from the PO, so not my fault guv…..

Thus, I think I am going to plump for the single SU HIF44 conversion as per the excellent one pager by Chris Hasluck on the bcmgoc website. It seems pretty straightforward, but perhaps a few Qs directed to those who know better than me.

Manifold could be an issue due to bonnet clearance. May get lucky I suppose, but the recommended Titan/Howley inlet manifold seems expensive and rare. Thus I was thinking of machining/filing the original BL part ----thoughts….

Any thoughts on main jet choice – or stick with whatever the carb comes with.

Any thoughts from those that have done the conversion on a similar car much appreciated.


Many thanks as ever
Mark O

Hi Mark,
I did this on my midget. It was worthwhile with better low down torque and of course only one carb to set up. I ended up with a Titan manifold but did machine up a standard BL part. It's quite soft so could use a woodworking router with a suitable jig. I still have it somewhere so it could be available for postage. I have some pics somewhere...probably posted on here a few years ago. If you let me know your email we can discuss off board. stevechurch314 at gmail dot com
Of course someone may come up with the proper manifold. I believe there were two types of Titan with different angles.
Steve Church

Steve - sent you a PM

If anyone else has suitable bits and pieces, I would of course be interested....
Mark O

Mark, that is a good move if you like simplicity

I do

There were two Titan manifolds (or even three if you take any notice of the story that Titan were producing a hybrid) The manifold for Sprite/Midget (which I have) and the manifold for mini and 1100/1300s. The hybrid is supposed to fit both types of A series, not sure whether... myself)

Several of our fellows hereabouts fitted the Metro manifold with modified flange angles to allow flatter fitment so the bonnet could be cleared

Others have reduced the height of the HIF damper by cutting down the dashpot and reducing the damper rod's length or fitting the flat top damper from a SU HS6

As to your jet question

No you don't change the jet, it is fixed diameter

You do need the right needle and spring combo

The MG Metro 1300 is fitted (generally) with a BDL needle and most people who've changed them around come back to this as the "correct" needle for the job on a decently tuned Spridget 1275.

If you get stuck let me know and I'll cast around for my little Austin-Rover data book for the Metro which also lists a couple of alternatives, possibly a little fatter round the tip. Who knows, the books are in storage at the mo' but I can look 'em out for a good cause

The spring, I think is "red"

Hope this helps a bit, I'm happy with my HIF

45-50 mpg ish

Quickly

Bill1

Bill

Thanks for that - I am currently on the lookout for all the bits - may have the manifold sorted - thanks to Steve, but anything else greatly appreciated.

Simplicity - yes indeed. Often greatly under-valued these days......
Mark O

I can't find my SU referenc book but if the carbs you have are H or HD type, especially in an inch and a half size they are probably worth more than the cost of a Titan manifold. Have you got a photo of them?
Daniel1312

Daniel

Photo for your delight - guess they may be pretty old, given the brass dashpot hex nuts. Originals - bits missing - to the right of them.

Regards

Mark


Mark O

Hi Mark, I went down the same route, Hif44 & Titan.
A BDL needle works well, Phidget flies, the better the faster you go (just up to the legal limit!)
Very easy to install and adjust.
Kept the heater transfer hose & pipe and used the manifold water pipe for the breather.
Cut down an ali. camping dish as an extra heat shield, the metro one is very small, felt the float chamber was a little close to the exhaust manifold.
Was rather paranoid about the distance between bonnet and damper top, I had about half an inch but thought if the engine rocked a bit we may end up with a dent in the bonnet, so I used a shorter damper (LZX1389) and cut the piston top down about 7mm-8mm to allow full piston movement.

Good luck,
regards Tony


Tony G

"so I used a shorter damper (LZX1389) and cut the piston top down about 7mm-8mm to allow full piston movement."

Hi Tony, I did exactly the same thing, and have always wondered if there's a significant trade of with loss off piston damping that might affect power. I've never been on a rolling road to find out, so I have no idea. Does anyone?
Lawrence Slater

I've just finished fitting a HIF6 (earlier version of HIF44) also using a BDL and going well. Better pick up and seems smother + better fuel economy.

Will be on Aldons R/R 8th December so will check power difference.

I've fitted a deep K&N filter with a very short ram pipe within. Also added a further throttle spring as it was too light for my boot !
Original throttle cable was O.K, but needed a longer choke cable - need to check but may have been MGA.

The Titans do come up fairly often on e bay just need to keep an eye out. Oselli also did one called a Torquemaster that is supposed to fit.

R.
richard boobier

Hi Lawrence, I doubt that cutting off the top section of the piston makes any difference, it was only the unused part which popped up into the raised damper top. The flat topped damper has a shorter rod and you get full damping along the whole length.
I would guess the spring weight and oil used would make a difference, I used a red spring.
Regards Tony
Tony G

Lawrence,
I meant power difference between the original 1.25's and 1.75 (just reread your post about dampers).

R.
richard boobier

Brass top twin H4s. I thought they sold for serious money but ebay doesn't think so at at the present time though they two sets I saw had plastic tops and have days to run. I think if I were having SU carburation on my car's engine I'd move hell and high water to get the twin H4s working as they look so neat and period correct. Having said that, the photo of the single HIF44 conversion is the neatest I've seen and if Tony wants to send me a copy of the photo you never know it might end up in a book one day. Or I'll try and find you when I'm next on the IOW on hols and take a photo myself.
Daniel1312

Hi Daniel, thanks for your comments. You are welcome to take some photos here on the Island, quicker if I email you a pic or two directly.
Regards, Tony
Tony G

I sold a pair of h4's to Japan for about £250 a few years ago that we're no near as nice as those.
John Collinson

Mark O
Glad you liked the article on the BCMGOC website. I agree with comments about the right needle. I tried all sorts but a session on a rolling road showed that BDL was the right one (even if slightly weak at max revs) for my set up (1330cc, MG Metro head, LCB etc.).

Regarding bonnet clearance, I had no trouble until I fitted new genuine Rover engine mounts which turned out to be thicker than the ones I orginally had (and which raised the engine/carb by around 3/4 of an inch and dented my bonnet). So one method of gaining clearance is to fit aftermarket mounts so as to lower the engine slightly.

One thing I found was that the Metro throttle cable was a little bit short and when streched over the heater trunking made the throttle rather jerky (it was fine with no heater trunking). So I now have a short tube (around 3-4 inches) fixed to the heat sheald and use a standard Midget throttle cable - problem solved.

I would not go back to twin carbs and there is no loss of performance - I clocked 109 bhp on a rolling road earlier this year.
Chris H (1970 Midget 1275)

Hi Chris, had the same problem with the length of the metro throttle cable. Made a small hole each side of the heater trunking and passed the cable through, smooth as silk.
Regards Tony
Tony G

I also have an HIF44 after reading Chris' article. I found a Titan manifold on ebay and I have used a very short stub stack inside a large red ITG air filter from Kim at Magic Midget. It is the air filter that rubs on the underside of the bonnet. I have filed an angle on the filter clip to provide a tiny amount of clearance.

My carb came with a BER needle. I was advised to try a BBW and it has been fine. In fact the profile is very similar to the BDL. I regularly get mid forties mpg, and I like to keep up with the traffic. I have used standard throttle and choke cables without any problem. See photo.



Mike Howlett

Hi Mike
The normal position for a choke cable is clipped onto the heat shield close to the throttle cable. You seem to have a different arrangement - is that a HIF44 or something similar?
Chris H (1970 Midget 1275)

Chaps

This is all good stuff - many thanks. Not too fussed over my old SUs - although I appreciate they do look rather nice. Rather have the increased performance/reliability/ease of adjustment than their looks - especially under the bonnet where they are not actually seen too often...

Can I tempt anyone with an exchange, in return for a decent HIF44?

Ta

Mark
Mark O

I also have the Hif44 with the BBW needle on the correct titan manifold 1330 11:1 compression, maniflow exchaust and 123 dizzy. According to Aldons rolling road, i seem to remember that they said 92bhp at the wheels and more importantly, apart from slightly lean at tickover (900rpm)pretty much perfect through the whole rev range, where it drops off a cliff at about 5500rpm.
My choke set-up is the same as Tony G's except that I have a cut down cable (it was about 6' long) off a Chevrolet, of all things!
frogeye Gary

Chris,
Just looking at my photo and realised it was during the rebuild before I had fitted the choke cable. The black thing going up vertically from the carb is the vacuum line to the dissy. Here is a photo (slightly out of focus) taken this morning showing my home made bracket for the choke cable. Note the piece of foam to stop the filter chafing on the bonnet.

I have my idle speed set at about 1100 rpm. Much lower and the engine is not smooth and can stall when the clutch is pressed. I suspect this is as much to do with the dissy as anything. It is a standard 25D4 with Accuspark contact-less ignition bits.



Mike Howlett

I didn't fit my choke cable for years, instead, in the winter I used to get under the bonnet and operate the choke manually, and fire the engine via the push on the solenoid.

Then, I had a brain wave. Fit the choke cable.

I fitted the ORIGINAL choke cable from the twin carbs, that I thought was too short.

Actually, the only bit that was too short, was the inner. So I joined a bit on to it, an inch or so, using a stripped single eletrical cable screwed connector. works a treat.
Lawrence Slater

I seem to be one of the few with the heater pipe through the manifold, so I'd better say there seems to be no detriment by using it the way it was designed!

MGRoverAustinRoverMoCo built the Metro that way, Titan and others designed their after market ones that way too so I kept it that way.

I get decent fuel economy, no heat inspired fuel starvation come the summer and the top end is fast enough to enable losing a driving licence very easily. :(

My choke cable is the original Midget one and it is a sharp corner at the heat shield mounted attachment.

Works OK though.
Bill1

Another Titan + HIF44. With heater pipe connected on a 1380

Love the performance, ease of setup (versus worn old twins) and economy that still baffles me - even when thrashed cross country.

http://www.eatworms.org.uk/mg-midget/projects/75-midget-frontsuspension

My Titan was advertised for a mini - and is the identical angle to the manifold that came with my HIF44 which came from an ital. (see pics in album above). Bonnet clearance is fine - no messing with angles or dashpots etc required.

I also ended up with the BDL (it had something else in originally) even on the 1380 and it behaves very well.
Dean Smith ('73 RWA)

Another advantage is that it makes undoing/doing up the manifold nuts really easy and accessible.
frogeye Gary

Just get an Weber or dellorto 45, can't be beaten.
Onno K

Funny enough, this is sitting right in front of me as i type this.
Apologies about the quality as just taken with my blackberry.


frogeye Gary

Ah yes Gary, but is there a vague chance it will ever grace Gaps's inlet tract?

Been a while huh...


(how's the gerabox saga going mate?)
Bill1

Mike,
I have the ITG filter with HIF44, but I fitted mine upside down. I bought a blank back plate and repositioned the holes. Everything is therefore much lower - although it makes removing the cover a bit fiddley


Geoff Mears

Bill,

With the help of Bob T, we're putting the enginge back in next weekend. I won't bother with the dellorto yet as the Hif seems to run so nicely. perhaps if I get the Frog onto a rolling road again next year, we'll try it with both to see what the difference is. In the meantime, it makes a lovely paperweight.
frogeye Gary

Gary. You'll never get the Dellorto in your car, as in the picture it appears to have shrunk. ;)

Bernie.
b higginson

Moss list a MT3603 manifold for a single HS6 for Sprite 1275. Would that do for an HIF44 conversion? Since the spacers between the two different styles of carbs seem to be the same item I assume the bolt holes line up. No?
Graeme W

Graeme,

That part is also listed for a Classic Mini so the angle may not be suited for a Spridget.
Doug Plumb

Geoff Mears, thanks for that suggestion about mounting the ITG filter upside down. I might try that. Good idea.
Mike
Mike Howlett

Another HIF setup.
Although not connected in this photo, I have since connect up the water pipes to the Titan manifold. Choke cable is standard Sprite version. Air cleaner is a DIY modification of a twin carb version and contains a trumpet.


Guy W

Apparently Burlen make an SU for the Harley Davidson motorcycle. If the dashpot 7 cover is used from that carb a Titan manifold is not required as a std manifold can be used without clearance issues BUT I dont know that they will sell the dashpot and cover seperately.
Alan
Alan Anstead

Hi Graeme,

Just to record it here as well. The HS6 and HIF44 will both mount on the same manifold. They share the same manifold mounting gasket.

The difference in size is that HS6 is imperial, and HIF44 is Metric.

HIF 44(mm) = 1.73 inches.
HS6 The H=1", plus the 6, where 6 is 6x1/8" = 1.75 inches.

The other major difference between the two is that the HIF is "integral float bowl" and the HS, is "seperate float bowl"





Lawrence Slater

That should read,

The difference in "throat" size is that HS6 is imperial, and HIF44 is Metric. But the mouting flanges are the same. --- According to SU Burlen.
Lawrence Slater

Here's a picture of my angled spacer. Others have done the same/similar.

According to the technical on the HIF, it can be mounted 0 degrees to 40 degrees downdraught.




Lawrence Slater

Ref the MT3603 from Moss they have replied:

<<Hello
Thankyou for your enquiry
The MT3603 is suitable for Mini applications only, a Sprite manifold is available from other sources but we do not currently stock it.>>

Errr....why show it on page A24 of the Sprite and Midget catalogue then?


Graeme W

Graeme, because they can!
You will get Nigel started now on how "the customer is always right" applies to Moss!
Guy W

yes I did think before about putting how Moss tell the customer he's wrong in spite of any evidence to the contary

but as I always put cross reference any information you get, with two difference sources if possible and especially where catalogue parts are concerned
Nigel Atkins

Guy: I experienced that when I bought two new front shockers. One was so loose the arm virtually fell under its own weight while the other needed a scaffold pole to move it. I actually drove over to Kingston as I didn't know which was faulty to send back. After great "discussion" about "you can't really tell till they are on the car" and me explaining I was carrying out their recommended proceedure prior to installation, they were taken round the back for "expert evaluation". Got two totally different ones back. They were halfway between the two in terms of force needed to waggle the lever arm!
Graeme W

Mark,

There is an Oselli Torquemaster manifold on e bay currently which I think fits - not tried one but seem to remember they used to sell them for Midgets.

Anybody else confirm this ?

R.
richard boobier

Hi Richard, I have a osselli torquemaster which
is supposed to fit, it mentioned in the A series
engine book. I also have webber 45 but no
manifold (bought for wifes B!) but ii think
I will give the HIF44 a go regards Pete K
P C Knightley

Gents

I think I am sorted wrt manifold. I bought a HIF44 off the web c/w standard BL manifold. If that fails to fit, Steve C above kindly sold me his machined face version.

Thanks for all the info.

Mark
Mark O

WRT machining the faces of mini manifolds:
I understand from threads that mini ("wrong") manifolds are set at 30 degrees where as the Titan was 10 deg. From playing around with a rough sketch I would not have thought there was enough metal in the flange at the manifold end to reduce the angle on the face from 30 to 10 degrees. Am I wrong on that?
If I am correct, presumably you finish up with a compromise where half the gain is from taking the angle back as far as poossible and then either fitting a tapered spacer (as Lawrence shows) or/and reducing the height of the HIF44 itself.
There seem to be so many variations in individual cars that what suits on vehicle (no bonnet dents) doesn't suit another by all accounts).
Anyone know about the Oselli spec?
Graeme W

Come on Mark O... you can't just say 'sorted' and shut a thread down with less than 150 posts! Where are the 'what's that motorbike?' diversions, or some references to films or rock albums no-one other than Lawrence knows about!
Anyway, there isn't enough confusion created yet about how to resolve the problem. And no-one has answered my post about the Oselli.
Graeme W

;) heh heh. Nice one Graeme.

And I too want to know about the Oselli now.
Lawrence Slater

Just for fun, I popped over to the 'Bay and searched "inlet manifiold"

pages and pages popped out including the Oselli and a few Metro and "classic mini" manifolds many of which look useable. Some will need reangleing some may not.

One guy in Swadlincote has a Midgetey Titan, think he wanted £139, no bids just a straight sale. :(

Or was it £189?

I'm getting old and can't remember

I am NOT buying another.

I have other ideas these days.
Bill1

Bill1: I saw that one too. He also sells "turnkey" conversion kits of refurb carb, the manifold and the various bits like heat shield, choke attachment and so on. Spridget specific £300
Graeme W

My HIF "conversion kit" cost 1/10th of that price, complete!
Guy W

Things go for silly money on the bay!

Though you can have a steal sometimes.
Just bough MG road cars vol 1 for 65 quid (pre war MG book that usualy goes for over 200.....)
Rather happy with that.

Then I see the people offering a kingpin and a bolt for 30 and wonder what they where thinking
Onno K

I gave my spare titan to Nick Cherryscoop as a retirement gift.
frogeye Gary

So now we have to ask

Hey Nick

Did you use it?


(good present Gary, make him stay in touch...)
Bill1

Chaps

My profuse apologies for curtailing your discussion. I work in the Oil Industry where time is squillions of dollars in lost oil production, plus, I clearly have no wish to deny any of us that precious commodity for our tanks and engines...so I shall return to my pumps and separators forthwith....

Jesting apart, I may well revert when I attempt to fit it up! Still arm deep in brake fluid at present....

Mark O

It was probably still attached to little blue which he sold.
frogeye Gary

This thread was discussed between 15/11/2012 and 29/11/2012

MG Midget and Sprite Technical index

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