MGB: Bought a B, hopefully minor engine issue

Well, I finally bought my first B. It is a BRG 79 that seems to be in pretty good shape and I am pretty excited. The first problem that I need to deal with is the engine. It seems to run rough at idle, has a pretty smelly exhaust (gas) and the gas mileage seems pretty low. The previous owner who was a mechanic (who really had no interest in MG's) said there was an intake leak, and when he sprayed in carb cleaner it the idle smooths out. It looks to have the original single carb. Before I order the gaskets and take it apart does this sound right?

Carb probably needs attention/rebuild if you plan to keep that carb.

congrats, welcome to the looney bin!:devil:

Welcome!

if it has the original Zenith-Stromberg carburetor, then get you a rebuild kit if you're going to keep it. The water chokes are problematic - here's a couple of sites that discuss them:

http://www.sterlingbritishmotoringsociety.org/files/choke.pdf

http://www.theautoist.com/zs_water_chokes.htm

Also, you're going to need the special mixture adjustment tool - available through Moss or VB or Gordon at the B-Hive.

A question - does Vermont have testing that requires you to keep the Z-S carb? If not, you might want to look at alternatives. The Z-S can be made to be reliable, and your car can run well, but other solutions may be less time consuming - but more expensive.

I'll let some of the other guys fill in the details - welcome to the learning curve! :)

Here is a super-useful checklist for checking out all of the cars systems in a systematic organised way. IMHO go over this list and be sure each item is 100%

http://www.theautoist.com/awakening_a_sleeping_b.htm

Many owners replace the original single carb with a duel SU carb intake and manifolds from a pre-'74 MGB. This will make the car run much better. Also, consider getting a quality rebuilt Lucus distributer as this will solve many problems. Ask for both of these on the Trader Forum and one of the trusted vendors there will set you up with the right parts for your car.

Good luck, and welcome to the madness!

the best thing i did for my 79 was change out the carb, now the Z-S makes a very nice book end in the shop for the manuals .
i tried put a kit in but that never solved my problems with it .

It might just be runnng too rich and need a tune up.
You might think about fitting mark one type twin SU's. If you local regulations allow it. Increase in power and they look great polished up..

Jon,
Good advice above. Let me break it down for you.

The carb on your car was put there by the factory for emissions, not performance reasons. Most suggest you dump it rather than waste much money on repairs. I agree.

Their are lots of used dual SU carb setups from earlier cars available out there. The single downdraft Weber is also available but may be a bit harder to find. Keep in mind you'll need the whole setup... carb(s), linkage, air cleaner(s) and manifold. I think the single carb would be better for your application, as its easier to install and to keep in tune.

Place a want ad in the trader section, or ask in this forum for further advice.

If the carb swap doesnt fully cure your problem, then I'd try swapping out the distributor or its internals as suggested above.

Your previous owner is correct in that a leak exists. Try it for yourself by spraying some carb cleaner around the base of the carb with engine running.

It could very well be that your only problem is a failed carb mounting gasket. It could also simply be that the carb is loose and needs the mounting nuts tightened.

Your original setup can be set to run well and give good mileage and performance using the resources above as guidance. It is just a matter of checking and setting everything to spec.

And remember that the Zenith-Stromberg you have does NOT run right with the air cleaner housing removed. That little detail has caused more than a few to pull out their hair.

Just don't pay someone else or throw a lot of money at it as you will most likely want to switch to SU's or a Weber down the line.

But in the meantime, give what you got some attention, and get to know your new B.

I recommend that every new owner get the factory manual and use it as a guide to go through the car and make sure that things that are supposed to be tight ARE tight, that things that are supposed to be set at .015 clearance ARE set at .015 clearance, and just generally set things right.

Enjoy

My 76 ran years for me with a single HIF 4 and a 25D dizzy that the PO had put on. That is until last November when I rebuilt everything and added an OD trans. Now have a rebuilt 25D from Jeff and a Weber 32/36. When the tax return comes, hopefully, I'm going to have a set of HIF 4's rebuilt and put them in.

Thanks for all the info. Once the checkbook recovers a bit from the purchase I will look into the new carb and probably a header. Would there be an issue with the brake booster with an earlier intake? For now I guess I will try and nurse the carb along till spring. I will get some carb cleaner and give it a shot. This weekend when I was out playing with the car I let it run up to 4500 - 5000 rpms in second gear. It really did not like that. It ended up stalling, then when I tried the old trick of popping the clutch (which for some reason this car seems to not do) to get it started it backfired like a gunshot. It finally restarted (with the starter) and then was like it was before. I guess too much fuel is pooling somewhere. The air pump was removed by the previous owner, but the air filter is there with the cover, though I did notice the cover was not on tight, will tighten that.

Backfiring is typically an ignition timing issue, but a vacuum leak compounds the problem...

Jon, there's a rubber diaphragm on top of the carb piston that may not like carb cleaner. If you're going to use the cleaner, go ahead and get a new diaphragm for about $5 and install it after using the cleaner. You may need it anyway. If the diaphragm fails, the car won't run. If you do replace the diaphragm, be sure to get the tabs on it back into the proper slots on the piston and carb body - they position the biased needle correctly.

Congrats on getting your first B! Now the fun starts!!
:beer:

I had very similar issues with my 78 when I got it. Very very rich running! I tried the re-built bit with the ZS but really got no where. I even had an expert help me with the distributer/ignition. All we did was make it run more reliably, but not much leaner.

I ended up going with the Weber downdraft because I wanted a relatively easy to install and set up plug and play deal. It works for me. The brake booster is pretty easy to plumb into the intake. Overall, the expense was pretty high ($750) because if you yank to ZS off, you will need a new intake and exhause manifold. I needed a new exhaust too, so I did the whole bit.

I am really happy with it at this point. No messing around with tuning, just drive and have fun. Good luck with yours and welcome.

The ZS carb is best used for a boat-anchor - it'll never rival a set of SU's. Please stay clear of a Weber too. HF-4's are the only way to go.