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 MGB Technical - On the single carb MG's can a Motorcycle carb be

used? If so which one would work and where is a good place to get one. The price of rebuild/new ones seem to be exorbitant.
Sammy A. Williams

Short answer is, I believe, no :o)

However, you can bet that someone, somewhere has tried it. I can't imagine that a pair of used SUs and an inlet manifold can really be that expensive though.

ttfn,
--
Olly
Oliver Stephenson

Check out the third issue of B+ Magazine. Lee Seats put a Harley carb on his B and its very quick.
Greg Bowman

For the price of a Harley carb and it's associatied plumbing, I'll bet you could get a new set of SU's. Harleys are 1200 cc, about 2/3's the displacement of the B. How are you going to force enough air through the venturi?
R. L Carleen

Sammy,
Last year, I built an 1800 from a 79 to use as my "aux powerplant" / emergency 110 generator/battery charger/livestock waterpump/ starter and alternator testbed, and shop central heating unit (still looking for an airconditioner....) I had a brand new Weber set aside, but had to use it for another project. I wanted something absolutely reliable that would start in any weather, and idle for hours on end without problems, and while I'm a diehard SU fan - swear by them - I only wanted/needed one carb, and as few complications as possible. I was doing this project on a near zero budget to boot, and the ZS that came with the engine was corroded to the point of being scrapped. I got the following idea from a PO of a B I inherited - they had rigged up a single barrel zenith downdraft carb using a bunch of waterpipe elbows and short nipples. It actually ran ok, considering how decidely low/no tech it appeared to be... so, I tried it my way....
For less than $20 total, I ginned up a carb and adapter made from 3 long sweep 1 3/4" aluminum pipe elbows, and a 245 cfm single barrel electric choke Holley from a junkyard early 70s Ford 6. I cut and drilled a carb mounting pad from a small piece of 1/2" thick T6 billet and sawed the base off of an old CD175 to mount to the stock intake. My TIG unit was out of gas, so I used a combination of Alumaloy (MAPP gas weldable aluminum alloy) and Martex epoxy to join the pieces, and make the runner smoothj and airtight. Considering the lack of engineering and utter lack of attention to the flow characteristics of a 3 turn, highly convoluted runner, it turned out just fine. The engine fired right up, idled smoothly and had excellent idle mixture screw and off idle throttle response but has not been tested on a vehicle.
I've since built another one for local ZS owners who need to borrow a carb. This one is made from 2" cast iron pipe elbows (2 street Els and one standard El to minimize cast iron brazing) with a downdraft 38mm Solex single barrel that happens to accept the stock throttle linkage without any mods. I martexed the mounting flanges to the els and dieground/martexed the threads in the flowpath. The choke is of the stove variety, and I simply lengthened the existing choke tubing to reach down to the exhaust manifold and fixed it to the 1/4" boss mounted holes that the ZS cold start tube was originally bolted to. It also has 2 vacuum pick offs - one metered and one from the downsteam side of the butterfly. I ground about 1/3 of the excess mass off of the elbows to cut down on the weight hanging off the intake. It ain;t pretty but it works just fine...
Both guys that have used it commented that it starts easier in cold weather and provides smoother and somewhat stronger acceleration than the ZS. Looks-wise, form went out the window in the bucksdown quest for pure function.... Maybe someone out there with more time could set up and test an adapter to bolt a Weber downdraft directly to the stock ZS intake. If it works, it would sure be a lot cheaper for anyone wanting to get rid of the ZS, but contented with keeping the stock exhaust.
mark c

I've done a number of oddball one-off carb setups, and the truth is, you can make just about anything run with just about any carb. Not well perhaps, but run. A carb that is smaller will almost always result in better driving characteristics though at the expense of WOT power. A larger carb will usually result in a max power increase but will often cause driveability problems, sometimes extreme ones. Motorcycle carbs will work. How well is another question, very dependent on what you use. Rejetting may be necessary, use of a motorcycle cable throttle, and the choke is often a lever on the carb itself. OTOH, it is possible to find motorcycle carbe with a throat as large as 2" so capacity should not be the determining factor.
Jim Blackwood

I saw an old Harley-Davidson with an S.U. carb on it once. It looked just like the HS4 on my '66B. The owner said he'd had the S.U. on the bike for at least a decade, maybe several from the looks of both of them. But I have to agree with the previous post, that you can get a pair of HS4s for less than most single carbs cost. If you need a later, more expensive carb, perhaps a twin HS4 conversion or the Weber DGV kit? Or a used Weber DGV?
Chris

This thread was discussed between 17/01/2003 and 20/01/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.