I don't believe the Weber is particularly different from an emissions
standpoint. I think what you are referring to is that many jurisdictions
require a visual inspection for original required emissions equipment,
and a non-original carburetor will cause you to flunk automatically. One
good thing in this regard is that very few inspectors have any notion
what to look for in cars of this vintage (certainly no references on
hand), so you can often breeze through this part so long as it isn't too
obviously kludged or race-prepped, and pass-or-fail on the actual
emissions results. This depends on your state of origin, of course, but
even in California you could get away with this. Now cars up to (or
through?) 1973 are exempt in CA, so it isn't an issue for many MGs.
Tab Julius had this to say:
>Thanks - that's very helpful. Seems to be performance and response are the
>factors. I understand that with the carb I also have to change the
>exhaust. What has to get changed to help choke diamter? Knowing this
>group, I'm guessing somewhere there's a recommended "List of Things To
>Change When Converting from a Zenith to a Weber". Know where that list
>However, going to a Weber will wait until I put OD in. That's a definite
>I know Weber makes it harder to pass emissions. We don't have emissions
>testing in my area, but I'm not looking to make some belching air-abusive
>car either. I'm not an enviro-nut, but I try not to be overly
>disrespectful either. What emissions part is the Weber particularly bad in?
>Thanks for the informative answers...
>At 11:08 PM 8/5/00 +0100, David Hill wrote:
>>Carbs all do the same job, though not necessarily in the exactly the same
>>way. Sometimes, the stock carb is restrictive so a larger choke diameter
>>will allow the engine to breather better at higher revs. However, there is a
>>great danger of overdoing this, so the gas speed is reduced to the extent
>>that the fuel doesn't atomise properly.
>>Engine tuning is essentially about getting a bigger bang to happen faster,
>>which is why much of the work involves allowing mixture to get in, though
>>and out of the motor as quickly as possible. This is why cam profiles and
>>exhaust/inlet flow get so much attention.
>>The other element of tuning is accuracy-i.e. balancing combustion chambers,
>>tweaking advance curves, etc. so as to make the events in the engine happen
>>in under tighter control. In this respect, a Weber is, arguably, a better
>>unit than a Zenith, in that its provision of the right mixture for different
>>conditions is more accurate.
>>Remember, though, a Weber on its own won't make a huge difference and the
>>additional mods depend on numerous factors, including choke diameter.
>>Hope this helps,
>>----- Original Message -----
>>From: Tab Julius <email@example.com>
>>Sent: Saturday, August 05, 2000 8:23 AM
>>Subject: What are the true benefits of a Weber carb?
>> > Today, a gorgeous day, I met two (count 'em: 2!) MGs driving in my town, a
>> > small town of 3000 people where I probably have the only one, unless
>> > someone else is keeping theirs tucked away.
>> > One was a B, the other a Midget. I talked to guy with the Midget, who was
>> > just passing through, and he told me how he had reconditioned his,
>> > including replacing the Zenith with a Weber. He said it was a definitely
>> > noticeable major difference, although he didn't elaborate (and by then we
>> > were out of time). I have a '78 B, and now I'm wondering, if I moved to a
>> > Weber:
>> > 1) What significant differences would I see?
>> > 2) What would be involved? Is it just changing the carb, or do I have to
>> > do the muffler too, or what?
>> > 3) For those of you who moved from a Zenith to a Weber, what did you
>> > think? How much did it cost, and would you do it again?
>> > TIA,
>> > - Tab
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.