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MG MGB Technical - no carb diet

I recently purchased a '74 B here in South Florida. It ran quite well with it twin carbs until one day, when it began to misfire, flooded itself, and stopped. A tow to the garage resulted in some carb adjustment. On the way home, the rear carb began to foul the plugs again and the front carbs began to overflow. The mechanic suggests a Weber conversion. I would like to keep the original carbs, which he reports are too far gone to rebuild. I wonder, though, why it ran so well for a few weeks... no problems at all... and now needs a Weber. I hear that this series of carbs (used on the'74 ) are not very good. Any thoughts out there? I am not particularly handy and there are not a lot of British car mechanics here. Thanks! BILL
Bill

I'd like to know what constitutes too far gone to rebuild. There are no real wear components that aren't part of the reuild. I rebuilt the HIF4 carbs on my '74, and it was one of the easiest and most rewarding jobs yet! The rebuild kits are inexpensive, and replace all bushings, throttle shaft, shaft bushings, jet, needle, seat, etc. as well as all gaskets and O rings. Certainly cheaper than a new carb. If you are not up to the job yourself, consider sending it a rebuilder like Joe Curto (Mr. SU).

Dave
Dave Whitehead

I will second Dave's suggestion to consider sending the carbs to Joe Curto for rebuild, his web site is: http://www.joecurto.com/

Since there are not a lot of Britich car mechanics where you live, I would also consider Post a query on This BBS and on the T series (TD & TF) BBS, for information on good MG mechanics from other MG owners in Florida (one who is perhaps a bit more knowlegable about SU carbs. It always amazes me how many incompentent mechanics who, when confronted with a SU carburetor immediately say they are beyond saving and should be replaced with Webers. You have a lot of MG company down there in Florida, so check around for a good mechanic. Good luck - Dave
David DuBois

Changing to a weber is a bit drastic just for what might just be a faulty float valve, and such conversions aren't always successful anyway. Get the twin SUs working right and you will be much happier. The only real point in sendeing them away for a rebuild is if the butterfly bushes are worn, anything else is a relatively easy DIY job. But overflowing could well be cruddy fuel if not the aforementioned float valves, or possibly a sunk float, so fix any possible faults first or you will just be wasting money.
Paul Hunt

Just to check, the current carbs are twin SUs? HIF or HS4 (float bowls off to the sides)? If so, rest assured they are superb, perhaps the best ever designed for road cars, so think twice about the advice of anyone trying to tell you they aren't up to much! There is always a ready market for them in any condition as parts are still available.
Steve Postins

Bill, I live in the Palmetto Bay area and I can tell you there aren't any British car mechanics anywhere around here.
Best bet would be Brooklands, Inc. in Ft. Lauderdale. Haven't been there myself as I've always done all the work on my B.
Perhaps if you contact me and you live nearby I can at least give you some pointers on whats happening and maybe adjust your carbs a bit. It seems, from what I hear, one of your carbs are flooding and your HIFs (if they are the originals)may need balancing.

Make sure you put MGs in the subject title as I tend to eliminate everything else.

Luigi
Luigi

Thanks, everyone, for your responses. I am not certain what model carbs these are. They are twin, but the floats are not on the sides. Years ago, I had a '67 B with the side floats. But, I am going to try to have these rebuilt.Or, if good used ones are out there, I might go with that option. Thanks, again!
Bill

Bill; If you buy used SU's you will probably also have to rebuild them. Your car should have HIF-4 carbs with the float chamber on the bottom. The problem you have is usually caused by the float needle valve as has already been mentioned. The HIF-4 neeldle valves seem to stick sometimes if the car isn't run for a few weeks and tapping them on the side doesn't help to clear the sticking as it does on the HS-4. Don't buy Grose jets for an HIF they only make them worse. If you have a non stock fuel pump it may have too much pressure, either change the puel pump or add a reguleator. I have owned cars with both types SU and I prefer the HIF. Good luck, Clifton
Clifton Gordon

Bill,

Before doing anything else, make sure the fuel sustem is clean - the symptoms you quote are often caused by dirt in the fuel system.

The carbs should be taken off the car and thoroughly cleaned out and then refitted with a clean fuel filter in the line just before the carbs.
Chris at Octarine Services

Rebuilding the carbs is easy. The throttle shafts are the biggest wear item and you can get the "turbo" seals for the shafts to get them to go another go without rebushing. Full kits are available with the shafts and butterflys and the shafts tend to wear faster than the bushes anyway (on purpose). The kits are not cheap but much less expensive than a weber kit!

Get new needles (seperate) the kits come with jets but the needles are spring biased and rub on the jet.

If the shafts are very wobbly (easily noticed once carb is out of car and "in-hand") then re-bushing is likely. Try extracting the throttle shaft a little way and wiggle again. If it all "stiffens up" then new shafts will be OK for now (with seals). I hear you all moaning but cheap is good, if effective.

#1 reason for HIF carbs to "suddenly" run rich is a failed o-ring in the choke circuit! I am betting you only find black paste in there!

Mike!
mike!

Thanks for all your notes and suggestions. Being not a handy sort, the wee beast is paying a visit to a new doctor, one who feels certain that we'll be back in the road in no time. Hmmm. We'll see!
Bill

This thread was discussed between 15/02/2005 and 22/02/2005

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