MGB & GT Forum

Welcome! Sign In Register
Please Sign In or Register to Search

Weber 45MCHH - Fitted but need adjustment.

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

Hello All,

Finally got the Weber 45MCHH conversion kit up and running and first impression is: What a difference!!!

The '78 now starts on the first click of the ignition (the ZS took 10-12 seconds of cranking) and I feel there is a considerable power gain and response in the car. The only issue I have is that at around 3000rpm and higher the car now seems to be searching for gas. The car stutters a little and backing off the gas pedal allows the car to 'catch up' and all seems to run better after a few seconds. If I keep increasing the gas when the stutter appears the engine behaves as if on 3 cylinders. I believe I have all tubing from the old ZS hooked up correctly.

However, to hook up the new Weber there is limited room for the air filter (see pics). The filter shrouding has to be bent in order to clear the brake booster. Could the air be restricted at high revs? Also, as this was a 'lightly used' carb I dont know if the PO has played around with the settings for the gas mixtures.

I have no docs with the carb and so was wondering is there a site showing the basic ball-park adjustments for a Weber 45 and the locations of the adjusters?

Any insight much appreciated, John

P.S. I intend to write up a full description of the fitting of the conversion kit in the hope it helps somebody else.
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info

Attachments:
1 (Medium).JPG (46.3 KB) –
1 (Medium).JPG

2 (Medium).JPG (47.5 KB) –
Please Sign In or Register to view this photo
magohn Avatar
John H
Woodinville, WA, USA   usa
1978 MG MGB

I just had a thought. I'm also using the air filters hose fitting to connect to the front tappet cover. Could this be the culprit?
Thanks, John
Gerry Avatar
Gerry Masterman
Prairieville, Louisiana, USA   usa

I'd try it without the aircleaners. I doubt the tappet cover hose can cause any problem if its hooked to the aircleaner. Does that carb have a choke? If so, when you think you are running out of gas choke it a bit and see if things get better. I really suspect the jetting of the carb is way off, giving you a lean mixture. Could be the float is set too low as well

What concerns me the seemingly complete lack of tech info on this carb on the web. Even the seller offers no details other than what is included in his kit and just a blurry photograph small enough so that no details are apparent



Signature removed at Skye's request



Edited 2 time(s). Last edit at 12/03/2006 04:53PM by Gerry.
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
magohn Avatar
John H
Woodinville, WA, USA   usa
1978 MG MGB

Thanks Gerry. These were my choke thoughts too. Unfortunately the only piece missing was the choke cable. I picked up a universal choke cable but now find out the 'single strand' type I bought wont work. The reason being the cable has to pass thru a 90deg angle and the single strand type inner cable does not have that kind of flexibility. I will hit Napa Autoparts tomorrow and see if they have a more flexible alternative.

As for the carb itself, overall I am extremely happy with my purchase. The carb is in excellent shape and retails for $300+. I got it for $175. The difference in starting and 'feel' is major for me. I will report back once I get the choke sorted.

The new tickover noise from my '78 reminds me of an old mustang. A really cool 'pop-pop-pop' throaty noise... smiling smiley

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

I wouldn't be surprised if that crushed air filter isn't at least part of your problem. From the looks of the pics, it seems that it almost certainly has to impede the air flow quite a bit the way the foam filter element is mashed down toward the throat. I may allow enough flow to feed the engine at low speeds...but not above 3000 RPM.

If that proves to be the problem, you may have to fabricate some kind of air box that'll clear the brake master and feed it through a hose to a remote filter.

It would be nice if that thick adapter plate could be made thinner to allow a little more room at the master cylinder. It doesn't look like it would make MUCH difference, but even 1/2" would help.






. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
magohn Avatar
John H
Woodinville, WA, USA   usa
1978 MG MGB

Thanks Joe. Apparently there is a fix for the clearance problem for free from Weber. They supply another mount that is set at a different angle that clears the air filter from the brake booster. I will call them in the tomorrow and also ask about a Choke Cable if no luck locally.

Thanks, John

JoeReed Wrote:
Quote: I wouldn't be surprised if that crushed air filter isn't at least part of your problem. From the looks of the pics, it seems that it almost certainly has to impede the air flow quite a bit the way the foam filter element is mashed down toward the throat. I may allow enough flow to feed the engine at low speeds...but not above 3000 RPM.
If that proves to be the problem, you may have to fabricate some kind of air box that'll clear the brake master and feed it through a hose to a remote filter.
It would be nice if that thick adapter plate could be made thinner to allow a little more room at the master cylinder. It doesn't look like it would make MUCH difference, but even 1/2" would help.


BManBrian67 Avatar
Brian M
HB, California, USA   usa
1967 MG MGB MkI "MI MG"
2000 Porsche Boxster S "Got Box S"

Hey, does anyone else have THIS particular model of 45 DCOE on their MGB????

Maybe, I've just not kept up with recent weber MGB models, but I've NEVER seen that model before.

One word of advice, you had problems with the car staring before, and now you have a different carb on and you're still having problems.

Maybe you have an ignition issue. I would check there FIRST.

That manifold that you're using, where did that come from?


. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
magohn Avatar
John H
Woodinville, WA, USA   usa
1978 MG MGB

BManBrian67 Wrote:
Quote: Hey, does anyone else have THIS particular model of 45 DCOE on their MGB????
Maybe, I've just not kept up with recent weber MGB models, but I've NEVER seen that model before.
One word of advice, you had problems with the car staring before, and now you have a different carb on and you're still having problems.
Maybe you have an ignition issue. I would check there FIRST.
That manifold that you're using, where did that come from?

This is the 'latest' MGB conversion kit. The manifold is the stock ZS manifold that the ZS mounts too. The kit allows the user to simply replace the ZS with the weber 45.

As for the problems they appear to be different issues. I have a gut feeling the Weber problem is a fuel starvation problem. I will get a choke hooked up ASAP to check.

Thanks much, John


BManBrian67 Avatar
Brian M
HB, California, USA   usa
1967 MG MGB MkI "MI MG"
2000 Porsche Boxster S "Got Box S"

Wow, learned something new. ain't life great!

Is that carb purpose-built for the MGB?

One thing with webers, the same carb can fit a 1200cc engine and also a 500 ci engine, and it'll look the same on the outside. But, the guts, the good stuff on the inside are completely different.

Inside the Haynes manual that is designed exclusively for WEBER carbs, they have charts of jets, venturis, chokes, etc., etc for each and every weber carb and all the applications (different engines/cars)

First off, before I spent too much money of fuel pumps, regulators, etc, I would make sure that you have all the correct jetting and venturis inside that weber.

I cannot explain enough how important the inside guts are.

brian

ps. (I'll check my weber book, but if that's a NEW carb, I doubt it's in there)

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

Thanks Brian. Yes the carb is intended for the MGB. Its atractive to people like myself who dont want to spend big $ on a setup as well as change out the exhaust header etc.
The unit bolts right onto the old manifold. Easy install. Hardest part was getting the 4 old studs out of the manifold that held the ZS. WD40 and an overnight soak took care of that.

Im really enjoying the 'new' feel of the car. Much more responsive and a blip of the throttle has the back wheels spinning. I feel like a kid again smiling smiley

Everyone may not experience the same difference as myself Vs the old ZS carb. MY ZS was really old, dirty and had various screws missing. The PO said it was rebuilt but after taking it off the amount of black gunge in the carb leads me to suspect that as non-truth. I guess technically it could have been rebuilt 10 yrs ago.

The main improvement for me is starting. The old ZS took 10+ seconds of cranking and pumping. This Weber starts the car on the first rotation.

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

Gerry Wrote:
Quote: I'd try it without the aircleaners...

Gerry, I think I owe you a pint of Boddies... smiling smiley

On the way home from work tonight I was getting the same problem of stuttering at high revs. I pulled in to the gas station and whipped off the air cleaner. The rest of the journey home the '78 literally 'flew'. No stuttering and held revs and 3k and 4k +.

Still provisional but I think you solved it...

I was having so much fun I took 'the long way home'. Turned a 9 mile commute into 22
smiling smiley

Thanks!

Weber is sending me an updated mount that angles the carb so that the air cleaner fits correctly.

Thanks much, John



Edited 1 time(s). Last edit at 12/05/2006 11:56PM by magohn.
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info

Reply to this topic or post your own questions!

Members Sign In if you've already registered, or

Register a New Account

Registration is free and takes less than a minute

Having trouble posting or changing forum settings?
Check the Forum Help File (FAQ) or contact the webmaster.


Join The Club

Sign in to ask questions, share photos, and access all website features

MGExp Menu

What's New

Membership

Forums ->

MGB & GT

MG Midget

Buy, Sell & Trade

Vendor Market

MG Engine Swaps

Original MG

MGA

MGC

MG Magnette

1100 & 1300

T-Series & Prewar

Modern MGs

MG Motorsports

Member Meetup

MG-2014 Event

Other Vehicles

Off Topic

Clubs

Forum Search

Random Topic

Latest Posts

Live Chat

Calendar

Journals

Tech Library

Car Registry

Cars For Sale

Model Info

Motorsport

Directory

Member Map

MGExp Store

Search Site

Advertising Info

Smartphone quick link
mgexp.mobi

Adjust Text Size

Larger Smaller
Reset Save