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"Fixing" Zenith Stromberg Emission Control Carbs


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"Fixing" Zenith Stromberg Emission Control Carbs

As some of you may remember I got '79 MGB recently. I was not real happy with the carb as it seems to be running too lean even with the misxture adjusted all the way to rich. Takes forever to warm up until it doesn't miss.

There had to be a way to fix it without buying a whole new carb.

Here is one way, I took the carb top off and then removed the piston and needle assembly

Dump the oil out of the piston so you don't spill it all over the place.

Turn the needle to all the way lean with the appropriate sized hex screw.

Remove the screw in the side of the piston that holds the needle assembly in, with any luck it will drop right out.

Next you will need a small stiff wire or the #68 or so wire drill bit I used to drive out the needle retaining pin--be careful not to damage the pin, it can be bent


Once you get the pin out you can pull the needle out. For a richer mixture you want it to go up further into the piston. Luckily the base of the needle is about .08" of an inch thick.


so I thought why not thin that out and then the needle can be up higher, essentially allowing a richer range of adjustment to the carb without changing the needle or needle taper. I did the filing by carefully and gently chucking the needle in a drill and carefully sanding, you must make sure you keep it straight and level. A drill press gently used would be better if you had one.


I took about half the thickness off and have just gone for a test run, it seems to have done the trick!

Reassembly is the opposite of dissambly as they say--don't forget to put dashpot oil back in.

Hope this can be of help to someone else--there may be better ways as well.

tony barnhill

Great Pumpkin - R.I.P
Re: "Fixing" Zenith Stromberg Emission Control Carbs

Question: Are all the preheat items (shroud & shroud tube, induction heater) for your carb in place & working?


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Re: "Fixing" Zenith Stromberg Emission Control Carbs

No, in fact if the history of the car given to me is correct the motor and intake exhaust manifold is from a '71 austin marina with a rebuild and a cam.

I believe I have the carb from a later B, the funky below the carb air filter is in place, but the induction thingy the goes up to the manifold is not, nor do I have it.

And while I understand what they were doing when they built it, I don't know why I would want to pre-heat the air going into the motor, as from everything I understand cold dense air is better than thin hot air for power.



Jedi Knight
Re: "Fixing" Zenith Stromberg Emission Control Carbs

Pre-heated air evaporates the gas better when the engine is cold.
Re: "Fixing" Zenith Stromberg Emission Control Carbs

yep, it has a bimetal flap that closes off the heated air when the engine warms up.
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