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Weber 45 MCHH Carb

Posted by RandMeyer 
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RandMeyer Avatar
Rand Meyer
Calhoun, GA, USA   usa
1980 MG MGB
I'm running the original ZS carb on my 1980 B and I'm need of either a rebuild or replacement. I'm leaning towards the Weber 45 MCHH replacement based on earlier threads and it being a bolt on replacement, but I'm wondering what else I need to consider besides the carb & #50 idle jet purchase itself. Some of the items I picked up on are:

1. Replace the heater pipe with the earlier straight pipe to address water choke lines.
2. Carbon cannister hose to air cleaner
3. Crankcase breather pipe to air cleaner
4. EGR valve pipe to carb
5. Missing heat shield - can I just purchase a new one for the ZS and use it or does the Weber require a different one?
6. Any distributor issues to be addressed?

I'm sure I missed some items from the earlier threads.

Thanks for your advice.

Jim and Kathy Buckalew
Kingsville, Texas, USA   usa
1977 MG MGB "Esmerelda (for Now)"
1978 MG MGB "The Parts Store"
1980 MG MGB Limited Edition (LE) "Elvira"
I thought about a 45 MCHH before also. I even called Webercarbsdirect and talked to them about the MCHH. All the tech would tell me was that I would be trading one headache for another. I opted for the Weber DGV. But it's your choise.

tim65mgb Avatar
Tim Guntly
Cherry Valley, Illinois, USA   usa
1960 Daimler V8-250 "SP250"
1967 Jaguar 340
1976 MG MGB
2013 Mazda 3
I would lean towards SU HS4 carbs over the webers.

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bleteaches6 Avatar
Lee Orphan
Bonney Lake, Washington, USA   usa
I put HIF's on my 80

mrobin Avatar
michael robinson
hendersonville, hendersonville nc, USA   usa
I have it and it was very easy to install. I blocked off all the items you mentioned and used a manual choke (also an easy install).
You should/must use some kind of heat shield for saftey reasons, I used the one of the zs carb.
So all in all it is a simple switch over, but that being really doesn't perform any better than the zs, mainly because of the crappy intake/exhaust manifold.
I would spend a little more money and switch to the dgv, or better still twin su's.


MT-B Avatar
Matt T
City, New York, USA   usa
I don't think the conversion to the MCHH would be very difficult and I think you hit on most of the fitting issues. The main drawback is that you are still stuck with that restrictive combination intake/exhaust manifold.

For my cars I have enjoyed the DGV carbs for a few reasons.
1)Reliability, I have put tens of thousands of miles on DGV's and never had any problems with floats, needle valves etc.
2) Simplicity, I have had mine hooked up with only a vacuum line to the brake booster and a vent to the side cover, that's it. In my car I like to keep everything as simple as possible.
3) Economy, I have never driven an MG with any other carb that makes it so easy to get really good millage.
I have also appreciated the fact that it's a pretty tried and true conversion so if something does go wrong someone here will know how to fix it.

I just got bold enough to remove my DGV in favor of a DCOE so I'm currently selling it in the trader section.

lewk Avatar
Keith Lewis
Cambridge, Ontario, Canada   can
I have installed the 45 MCHH on my '75 and love it, see avitar and attached

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P4260176.jpg    53.6 KB

RandMeyer Avatar
Rand Meyer
Calhoun, GA, USA   usa
1980 MG MGB
Thanks for all the feedback. I'm still confused as to what to do long term, but in the short term I will go ahead with the heat shield and a rebuild of the ZS. Will the heat shield address the vapor lock issues I have experienced after the car sits for a few minutes?

Thanks again.

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