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Weber 45 MCHH MGB Conversion Kit - Any Good?

Posted by magohn 
magohn Avatar
John H
Woodinville, WA, USA   usa
1978 MG MGB

Hello All,
New to the forums and previously posted about options to fit a weber to my 78 MGB. It appeared that I would have to ditch the ZS 'all in one' manifold and pick up an earlier exhaust manifold and a carb manifold for the weber. Then I would have the problem of the new downpipe having two couplings that do not match up to my single exhaust coupling on my 78.

Well, I just came across this conversion kit for $300 or so that claims to bolt onto the stock ZS manifold. How good of a carb is this? Does it compare well to other Weber options? I'm simply looking for a replacement to my finicky ZS carb with a little more punch...

details:
http://www.racetep.com/mgbmcch.html


Thanks, John
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yesiownanmgb Avatar
Zack A.
Abbeville, LA, USA   usa

That is interesting. I've never seen that before.

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Jon Zaremba Avatar
Victorville, CA, USA   usa
1979 MG MGB "Brian"

Wow! I am wondering if that would be acceptable for emissions testing here in CA? The retailer is in North Hollywood...

I've never seen this before either.

Has anyone used one???



Jon Zaremba

mrkenmgb Avatar
Ken DeLEEUW
Ormond Beach, Florida, USA   usa
1975 Triumph TR7 "Old Yeller"
1976 MG MGB V6 Conversion "Boynton Blue"

I wonder if they offer an electric choke? For some to install the manual might require the dash to be removed to install the manual choke. I had a water choke on my 76 and no need for the manual choke in the dash.
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JoeReed Avatar
Joe Reed
Cordova, Tennessee, USA   usa
1978 MG MGB "Kermit"
1997 Jaguar XJ6 (X300)

No need to remove the dash to install a manual choke. I drilled a hole just below the bonnet release and ran the cable through there - with the knob installed in place of the useless dashlamp dimmer switch. You could just as easily install it using an underdash bracket.




magohn Avatar
John H
Woodinville, WA, USA   usa
1978 MG MGB

Hello All,

Well I hope I dont live to regret it but the same exact kit was just listed on eBay for $200 'Buy It Now'. I 'made an offer' of $175 and the seller took it. Supposedly, the seller only used it for a month on his MGB before selling the car. As new condition with all fittings. Back to a manual choke smiling smiley

Im just happy to be getting rid of my ZS carb. I have nothing but trouble with the ZS and the water choke from day one. I was also hesitant about the extra work of fitting a different manifold setup and the expense.

Question: do i just pick up a new lower hose with no water choke bypass as I dont have a water choke anymore?

I will report back how it goes. Thanks for the input.

John
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Jon Zaremba Avatar
Victorville, CA, USA   usa
1979 MG MGB "Brian"

John,

I'm in the same boat as you. Please let us know as many details as possible once you get the kit and start driving.



Jon Zaremba

JoeReed Avatar
Joe Reed
Cordova, Tennessee, USA   usa
1978 MG MGB "Kermit"
1997 Jaguar XJ6 (X300)

You can just run a heater hose direct from the radiator hose to the heater and eliminate the water outlet on the rear of the head as well. You CAN just cut and plug that hose, but a blanking plate is much neater. Just cut one out of a piece of metal using the water outlet base as a pattern - and cut a gasket to match. I used aluminum stock the same thickness as the base on the outlet. Dab a little black paint on it and no one will know it's there...




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fleshy1 Avatar
Eric Triplett
Monrovia, CA, USA   usa
1978 MG MGB
2005 Audi S4 Avant "The Sled"

Check with rattlecanb on this one. He did the conversion and just recently had a whole custom intake made up for it.

I understand that there are some clearance issues with the air filter and brake master cylinder/booster on this conversion and that you must route the PCV pipe from the tappet chest to the air filter.



Eric Triplett
"Electronic ignition, the greatest thing that ever happened to carburetors."

1968 High Compression Engine, Dual SU HIF-4 Conversion, Peco Header and Exhaust, Pertronix LU-147, MSD Blaster 2 Coil. Advanced Distributors Re-Cruve 45DM

magohn Avatar
John H
Woodinville, WA, USA   usa
1978 MG MGB

Thanks all. John
JohnCleirigh Avatar
John Cleirigh
Colorado, USA   usa
1977 MG MGB "Ernie"

Hi John H,

How did your 45 MCHH install go? I'm about to pull the trigger on this as well, and I'd love to hear about your experience first. Thanks,

john
gatorbrit Avatar
Richard W
Raleigh, USA   usa
1977 MG MGB

JohnCleirigh Wrote:
Quote: Hi John H,
How did your 45 MCHH install go? I'm about to pull the trigger on this as well, and I'd love to hear about your experience first. Thanks,
john

Hi John,

There are several of us who have installed this carb, although it is a newer one on the market and there is not much collective knowledge so far about it. I installed one a month ago because I wanted a low cost and simple replacement for the stock ZS.

Here is what I have learned from my experience and that of others.

Overall the installation went well, but I do have a couple of pointers.
1. Earlier posts on this carb talk about an issue with the carb not fitting with the brake cylinder. This is not an issue now as the most recently shipped versions have an aluminum block that changes the angle of the carb slightly and makes it fit nicely.

2. The most important thing is to ensure that the carb is installed without any vacuum leaks. These are most likely to occur between the aluminum mounting block and the heat shield plate and between the plate and the manifold. A leak will result in VERY inconsistent idle and racing of the engine at certain times. So pay very close attention to getting this part of the install done right. Make sure that the aluminum block is bolted on very tightly to the manifold.

3. Pictures of the kit include an O ring washer that is supposed to go between the carb and the aluminum block. This is no longer included in the kit and it has been replaced by a thick cardboard gasket.

4. There are only two screws to adjust. One adjusts the idle an is pretty easy. The other, the idle mixture screw takes a bit more finessing. About 4-5 turns from its lowest point seems to work pretty well.

5. My car benefited from 2/3 of a can of sea foam drawn through the manifold. That really helped.

Overall I strongly recommend this carb if you want a simple and low cost alternative. If you want something that will significantly change the power of the car then this carb may not be for you, although there is no doubt that it did increase the power quite a bit.

Finally, you will end up with a lot of excess vacuum hoses that you have to figure out what to do with. There are posts that will tell you how to handle these or you can post and we can offer suggestions.

Good luck and let us know how it works out.

Richard




My Blue 77 B is gone after being totaled in a wreck. But the blog is still here...

http://1977mgb.blogspot.com/
magohn Avatar
John H
Woodinville, WA, USA   usa
1978 MG MGB

What Rich said ... smiling smiley

However, I had less of a gasket issue as I did not refit the heatshiled. My setup went:

Manifold->Gasket->Adapter->O-Ring->Carb - no gasket goo, just used what pieces came in the kit.

I also plan to fabricate my own heatshield.

Performance: I love it. The big thing for me being getting back to a manual choke ( I used the useless dimmer switch location to mount it). Very reliable carb so far and does give a nice punch upgrade over the ZS. Very easy carb to setup if this is your first weber. Just bolts right on.

I paid $175 for mine on eBay as it was only used for a month n the sellers car. (He sold the car apparently)

HTH

John
JohnCleirigh Avatar
John Cleirigh
Colorado, USA   usa
1977 MG MGB "Ernie"

Thanks guys! Richard, I actually found your 'blog before I found this forum thread. And John, I've worked on carbs for 20 years...(foreign, domestic, aftermarket) this design and application seemed almost too good to be true. I'm really glad to hear good results with it...and also glad to hear Weber worked out the brake booster kinks already.

I'm really done with the ZS! My first car was a '71 Volvo wagon with dual SUs. The ZS is so not an SU. And I've played with DCOEs enough to know I really don't want that headache on my 77 B.

I changed my distributor a while back and already eliminated the 4th gear vacuum line, so cleaning up the rest of the vacuum lines will make me happier. I have a manual choke already. On the ZS, the choke is not an air flap tho, it richens the mixture by adding fuel rather than eliminating air. Does the MCHH have an actual choke flap?

I have a hard-to-find exhaust leak somewhere around the cat that continues to clog the stock air cleaner, making for very rich running, and I'm a little worried about this open-element foam-type filter, so I guess the exhaust is my next project. Maybe it's time for a header?

Thanks again for the responses,

john
Craig in Niagara Avatar
craig smallman
Niagara Region, Canada   can
1975 MG MGB

I just did this carb conversion from the ZS on my 75 MGB. All in all, it went very well, and the kit fit like a glove. No issues at all with clearence. Like many posts here, I used the redundent dimmer in the dash to mount the manual choke. Routing the choke cable was a challange that would have benefited from smaller hands.

One thing I'd like to underscore. John C spells out the woes of not getting the carb sitting tight and the resulting vacuum leaks. My idle is rough, and the engine races at times during idle. I have sealed all the hoses in the manifold, so I suspect the carb mounting is leaking. I like the idea of doing away with the heat shield to reduce the number of gasket joints between the carb and the manifold. (This may be a silly question, but how critical is the heat shield?)

As for the end result; I could not be happier. The throttle response is greatly improved, and there is a nice little punch up in the horsepower. Even the sound of the car has improved.
gatorbrit Avatar
Richard W
Raleigh, USA   usa
1977 MG MGB

Craig in Niagara Wrote:
Quote: My idle is rough, and the engine races at times during idle.

Craig, i have to be honest and say that I have the same issues with my MCHH. I took it off - re-tightened it and still have an inconsistent idle. I did see a performance improvement, but I have decided to ditch the MCHH and go with a weber 32/36 DGV and a new exhaust header and pipe. I am also planning to have it professionally installed as I don't think I am up to the job. It is going to be expensive, but at the end of the day it'll boost the hp significantly and run much more smoothly. So I don't know that I would wholeheartedly endorse the MCHH anymore.

The heat shield is pretty important especially if you have the catconverter mounted as that can get very hot. The MCHH sits right above that and excess heat could cause vapor lock (or fire!)





My Blue 77 B is gone after being totaled in a wreck. But the blog is still here...

http://1977mgb.blogspot.com/
JohnCleirigh Avatar
John Cleirigh
Colorado, USA   usa
1977 MG MGB "Ernie"

Craig in Niagara Wrote:
Quote: My idle is rough, and the engine races at times during idle. I have sealed all the hoses in the manifold, so I suspect the carb mounting is leaking.

Hi Craig. I actually just ordered my MCHH and it arrives on Friday. I drive at altitudes from 5k feet to 12k feet so I talked to the tech at webercarbsdirect.com at length about re-jetting. The MCHH is not as complicated at the DCOE, but it is a similar carb, albeit a single barrel. You might find swapping out your idle jet will help improve things a bit. I ordered the carb with baseline jetting (read: sea level) and will then order new jets after I see the install sheet with the baseline numbers. The tech would not open a box to read the baseline numbers to me (maybe could not?), and the pdf is not available online yet at any Weber dealer's site. So, I'll report back what I find next week after my install.

Quote: I like the idea of doing away with the heat shield to reduce the number of gasket joints between the carb and the manifold. (This may be a silly question, but how critical is the heat shield?)

Well, with the MCHH the float bowl might boil if you still have your cat, even tho it's got some metal under it. With a well-insulated header, you might be okay w/o a heat shield. The engineers clearly thought it was an issue with the ZS. The float bowl on the ZS is right on top of the cat w/o the heat shield in place.

Quote: As for the end result; I could not be happier. The throttle response is greatly improved, and there is a nice little punch up in the horsepower. Even the sound of the car has improved.

The funny thing is I am not disappointed with the throttle response of the ZS, but at WOT it stumbles horribly. It idles smoothly and drives great with conservative right foot until the float jams, the valve sticks open and floods out. (the p.o. also installed an aftermarket fuel pump and this may be providing too much pressure to the poor ZS.) But after taking the ZS apart so many times to unstick the float, I'm done. <grin>

I'm happy to read reports of increased peppiness and I'm sure with a little tinkering we can work out the idle issues.

john





Edited 1 time(s). Last edit at 08/01/2007 02:28AM by JohnCleirigh.
Craig in Niagara Avatar
craig smallman
Niagara Region, Canada   can
1975 MG MGB

Thanks for info on jets John, and let me know what you do next, or what you find out about the jets. I should be all right as I am closer to sea level (Niagara falls area, same elevation as the great lakes). I will be spending the next little while tinkering with the carb, making adjustments, and checking for vacuum leaks. Nothing new there being an MGB, but if swapping jets helps, I am all ears.

Common sense is also telling me to leave the heat shield in place, or at least make a new one if I want to get rid of the plate between the manifold and the new carb.


JohnCleirigh Avatar
John Cleirigh
Colorado, USA   usa
1977 MG MGB "Ernie"

Craig in Niagara Wrote:
Quote: Common sense is also telling me to leave the heat shield in place, or at least make a new one if I want to get rid of the plate between the manifold and the new carb.

My car's p.o. also painted the cat with some sort of silver coating to reduce heat. It's flaking off. I wonder if using header wrap on the cat would be of any benefit? It would send higher temps downstream into your pipes and under your legs.

At this point my biggest cat issue is the exhaust gas leak. The escaping carbon is sufficient enough to clog the stock filter element in very short order. It's not noticeable by seat-of-the-pants evaluation, but on the scope and hooked up to a tail pipe sniffer, the difference is huge.

john


Speedracer Avatar
Hap Waldrop
Greenville, SC, USA   usa
1967 MG MGB "The Biscuit"

Byron, that's helping on Andy Russell's rally car build has 1980 LE and he just installed one, said the installation was striaght forward, and the car cranked right up idled and ran fine, he's very pleased so far.



Hap Waldrop
Acme Speed Shop
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