MGB Upgrading Carbs on a 80 MGB

[karls59tr]

Hello MGB Afficianadoes I'm visiting from the Triumph Forum. My brother has an 80 MGB that still has all the fedralized pollution devices on it. I'm trying to convince him to switch to the earlier twin carb version of B that others have done.That would really wake the motor up. What would it cost(ballpark) for parts. I'm assuming I could pick up most everything on Ebay. I guess the timing and maybe the dist. would have to be changed. Is there any info anywhere on this conversion. Karl

 

[Stewart]

It all depends. Some times you can pick up a set of carbs up with both manifolds for less than 200 bucks on ebay plan on spending 350 or more to have them rebuilt to better than new plus parts for the manifold and air cleaners. Plan on 100 for a rebuild and recurve for the dizzy.

I would say if you could do it for around 800 or so for a killer set up.

 

[rick_ingram]

You are correct...the dual SUs do wake up the car.

The dual HS4 or HIF4 would be a good choice. Be aware that he will be limited to air filter choices due to the small tolerance between the rear carb and the brake booster.

He will also need to run a manual choke (no big deal)..as well as a separate intake manifold and exhaust manifold and down pipes.

Another option is the single HIF44 (or HIF6 or HS6) that is a bolt-on to the MGB combo manifold. I did this conversion to my 1978 MGB back in 1991...and converted to dual HS4s about 2001.

BTW...I recommend keeping all of the intake equipment and emissions equipment removed...just in case it needs to be reinstalled at some point in time.

 

[tony barnhill]

& you'd better be able to get everything for the setup...there's 1 little bracket you'll need for the accelerator cable - they're NLA!

Or, you could solve the real problem with the setup - & it isn't the carb!

The real problem is the manifold.....cut the exhaust portion off the manifold - easy to do with a sawsaw - & use an early exhaust manifold & head pipe!

 

[karls59tr]

Anyone know anything about the "Aircare"(Exhaust emission test) policy in Vancouver BC ? I'm wondering if my brother switches over to dual carbs on his 80 MGB if there is a "new" set of emission standards the car has to meet as compared to what it was before? Wonder how that works? K.

 

[bigjones]

Another option is the single HIF44 (or HIF6 or HS6) that is a bolt-on to the MGB combo manifold. I did this conversion to my 1978 MGB back in 1991...and converted to dual HS4s about 2001.

Rick,

Was there much difference in mpg?
I'm thinking of converting my Midget single ZS to a single HS4 - I could justify it if there is a improvement in mpg (currently 22 mpg, and I'm a geezer)
(BTW, if anybody has a rear HS4 for sale please PM)

Cheers,
Adrian

 

[billspohn]

Don't overlook the fact that twin carbs don't convert a late smogger engine to early spec. There is still a minor difference in the cam and a major one in compression. They will certainly produce a big improvement though.

Not sure about how AirCare treats backdated cars. At the ;east you'd have to pass as a 1980, not an earlier twin carb car (it goes by model year) and if you made it 'dirtier' with the conversion that could be a problem.

Best suggestion is that you call Octagon - they wil know right away what AirCare practice is and what you can, and can't do/get away with.

 

[rick_ingram]

Another option is the single HIF44 (or HIF6 or HS6) that is a bolt-on to the MGB combo manifold. I did this conversion to my 1978 MGB back in 1991...and converted to dual HS4s about 2001.

Rick,

Was there much difference in mpg?
I'm thinking of converting my Midget single ZS to a single HS4 - I could justify it if there is a improvement in mpg (currently 22 mpg, and I'm a geezer)
(BTW, if anybody has a rear HS4 for sale please PM)

Cheers,
Adrian

Yes...I was getting 23-24mpg highway miles with the ZS175. With the HIF6, the numbers highway numbers were consistently above 30 (not a lot above 30..but above).

 

[tony barnhill]

One more time, guys, the problem is not the Zenith Stromberg carburetor.

The problem is the crappy manifold.....get rid of the combined manifold with that catalytic converter & all your problems go away...power is up as is gas mileage.

And all you have to do is slice the exhaust portion off the manifold & use one of the earlier manifolds.

Think how many cars use the ZS carb in singular or double form...TR8, 250C Mercedes, early ROVER V8's just to name a few.

 

[rick_ingram]

Tony...I had a crappy ZS175...and did not want to rebuild it.

My conversion was done more for a conversation starter than anything else...and it happened to work out quite well....just not quite as well as the dual SU conversion that I did later.

I agree with you that is the design of the manifold...not the carb...but this conversion does work fairly well.

FWIW - YOMV

 

[tony barnhill]

Rick - I did the single ZS carb/early manifold setup on one of my cars....somebody wanted to buy it after they drove the car, so we removed it & replaced it with a dual SU setup - couldn't really tell a difference. Then, when I decided to do a V8 conversion on the car, I sold the dual setup.

If Karl has a good ZS that doesn't need rebuilding, he could have the manifold problem solved on a Saturday afternoon!

 

[glemon]

Tony, my MGB (80) has a manifold from a '71 Marina, or at least that is what the previous owner tell me, not cat. converter, but a single unit intake exhaust manifold, previous owner said he thought or heard this was a better unit than the late B one, do you know anything about the early 70s Marina manifold?

It is a single carb manifold and I too am thinking of converting to a dual carb.

 

[tony barnhill]

No, but I'd like to see a photo if possible....is it the same design as a ZS manifold?

 

[rick_ingram]

Tony, my MGB (80) has a manifold from a '71 Marina, or at least that is what the previous owner tell me, not cat. converter, but a single unit intake exhaust manifold, previous owner said he thought or heard this was a better unit than the late B one, do you know anything about the early 70s Marina manifold?

It is a single carb manifold and I too am thinking of converting to a dual carb.

Does it look like this one? (Photo from Jimmy Hilton)

 

[glemon]

Well, I know it isn't that clean, I will take a look when I get home has a later ZS 1.75 emission control carb hooked up, I really feel it runs too lean, wish I had an SU, know how to work with them a little better, but I am sure I could come up with one with a little looking around.

 

[glemon]

Rick that is it, do you know anything about the setup, I was thinking about going to dual carbs, but maybe I just need to go to a good old SU if manifold flows well enough, it looks like a pretty good exhaust setup.

 

[tony barnhill]

ZS carbs do involve a little different touch when setting them up....also, if your ZS has a water 'choke', it probably needs to be cleaned (https://www.theautoist.com/zs_water_chokes.htm for a tip on how to do it)...if Mercedes chose them for their 250C - one of their classic cars - there can't be anthing wrong with them performance-wise...& the TR8 flies with them as do the older Rover V8 cars....Jag's like ZSS carbs, Volvo's also....aand the list goes on.

So, why don't they work on MG's? The design MG engineers used to get fuel into the engine & gases out....those things are what gave the ZS its bad name!

If you guys don't want them, I'll pay the shipping for you to send them to me!

 

[glemon]

I had Zenith Strombergs on my TR4 and thought they were every bit as good as SUs, it is the emmission control ZS that I don't like. I can't seem to get them to run rich enough. I would be just as happy with a 60s Stromberg or SU, but not a late 70s one, mine has a manual choke. I am not even absolutley positive that the mixture is my problem, may have too much cam in the motor--I bought is as is and I think if I were doing it I would have gone with a little less cam and a little more compression as it has NO low end to speak of but does get up OK past 3,000 RPM or so.