Single zenith carb is a joke...

[mgbmedic]

...I hate this Zenith set-up. I have no idea why MG created this, a carb for people who don't know how to use a choke?
I'm looking at installing the Moss SU conversion to eliminate a choke/starting problem. Anyone out there install this?

 

[AlanT]

The Zenith carb was a federal mandate. The feds did not think that you had the mental capacity to operate a manual choke correctly. (you might leave it on too long) If you can get away with it , install a set of HIF4's from a 72-74 MGB.

Alan T

 

[Bob Claffie]

I was very unhappy with HIF's on my '72 and eventually converted to HS4's which worked very well. Still have the (mostly) complete HIF set-up for any one contemplating such a change. Bob

 

[AlanT]

Both the HIF4's and HS4's are fine when set up properly. The HIF4's have a better but more unforgiving enrichment system and seem to work better with an anti-run on system.

Alan T

 

[kbash]

I extremely dislike single zenith, I'm doing my first Su switch tomorrow with the exhaust, I have a set of HS4 that are going in.

 

[Bret]

I too have nothing kind to say about the Zenith Stromberg carburetor setup. But when I first got my 78B I had every intention of removing it once it was exempt from emissions testing. Hadn’t decided for sure but I was thinking about a set of SUs rather than a down draft Weber for a more British look & feel.

However that was well over 8 years ago and life has a funny way of throwing curves at even the best laid plans. For years Kalifornia vehicles got exempt from all emissions (smog) testing at 25 years. Then a few years ago they raised exemption to 30 years for a short period of time, before this state’s lawmakers changed the rules again to “no exemptions” for “any” vehicles from 1976 forward. What a cruel deal that was (is) – seeing the light at the end of the tunnel – only to be blinded by hot pokers.

Today I’m a bit indifferent about the Zenith single carb setup mainly due to years of getting to learn how to work on it & running properly (mainly out of necessity) if I wished to keep it legally registered on the road. While I don’t have any sympathetic words for the ZS, fact is – it is a bit complicated & touchy to adjust properly – especially for someone not familiar with them.

Never thought I’d hear myself say this – but I do feel the Zenith Stromberg CD175 gets a bad rap, not because of the poor design as much as it’s application in this case. Because once you’ve properly adjusted the carburetor as part of the “entire” setup – while it’ll never be a real performer like a duel SU set-up, it does run surprisingly well. As anyone who’s ever worked on one for long will tell you - the really bad part of the whole setup isn’t really the carb as much as it is the restrictive manifold.

That said I feel have the answer to my ZS & emissions woes. The Moss EFI kit is sitting in a box in my garage awaiting to be installed on a “new” engine I’m building up for installation later on this year (hopefully!?!). /ubbthreads/images/graemlins/rolleyes.gif

 

[mgbmedic]

Moss has a single SU conversion kit...anyone tried it? Bob, I'm interested in what you have. By "mostly complete" do you have the exhaust header also?

 

[tony barnhill]

Just box up & send all your old ZS stuff to me - I'll pay the shipping....& down the road when you need them, they'll be on my shelf!

 

[Bret]

The single SU conversion is indeed a direct replacement for the Stromberg and will bolt up to the existing location without having to replace the combination intake/exhaust manifold – so no – you don’t need the header.

I’d considered this but it is not CARB certified and as such not really legal for vehicles that still need to pass strict emissions testing like we have here in Kalifornia. If you don’t have to do any smog testing – then it shouldn’t be a big issue. But you’d be spending big bucks to replace the ZS carb and still be stuck with the restrictive manifold. If you’re going to go that route – I’d save a little money & just convert to a manual choke. Because the choke (enrichment device) is IMHO the only real Achilles heal of the Zenith Stromberg.

But if my B was exempt from smog testing and I was planning on removing my ZS setup – I’d spend a few extra bucks ($$) & replace it “all” with a duel SU setup.

 

[Mickey Richaud]

[ QUOTE ]
Just box up & send all your old ZS stuff to me - I'll pay the shipping....& down the road when you need them, they'll be on my shelf!

[/ QUOTE ]

Opportunist! /ubbthreads/images/graemlins/jester.gif

Mickey

 

[Bob Claffie]

MGBMedic, I have both the intake and exhaust manifolds. No headers. Also the air cleaners. The HIF's themselves should be rebuilt. The only thing I am fairly sure is missing is the connecting shaft that ties the two carbs together. In fact I MAY have the shaft but used some of the small pinch linkage pieces on the HS4's. Exhaust manifold may need some studs, haven't looked at it lately. Bob

 

[Dan_D]

Bret, I agree with you. The ONLY issue I have had with my Z-S is having to replace the float bowl gasket. In 18 years of off-and-on again use, it's always been fine for me.

Dan D

 

[tony barnhill]

Don - I've given up on trying to get people to understand the ZS carb....I also have over 100,000 miles on my '79 that's bone stock original - carb's been rebiilt once & only then because car was in storage for 3 years.....never had any problems with it! Usually, its not the carb - its PO's lack of maintenance & band aids instead of correct repairs/maintenance! No ZS, if the 'water choke' is kept clean & properly adjusted ever needs a 'manual choke' modification; ZS's are way easier to adjust than twin SU's; & - though part of a package federally mandated to choke the car - does exacly what its designed to do...

Have you guys noticed there are V8's out there with factory dual ZS's that are fast as...well, I can't say it....but fast anyway?

 

[capitalcitycars]

I replaced mine with a Weber. I would replace the Weber w/ a Holley in a heartbeat if I could figure a way to do it.

 

[Hap Waldrop]

Just get a good used/rebuilt set of twin SUs from a earlier MGB, I like the HS4s better, but that's just my opinion, many like the HIFs, but with a header and the twin carbs you'll probably pick up 25 horsepower over the late carb/exhaust set up. I'm finishing a engine on 80 MGB for a customer as we speak with the cross flow head, twin HS6s, header and Pierce Manifold new cross flow head cam, ought to be interesting, we're going to take it to the chassis dyno for final tuning, I'll be sure to let you guys know how that turns out.

 

[Nunyas]

IMO, the factory ZS is merely adequate. It certainly doesn't do a lot in helping the late model Bs "get out of their own way". Then again, a lot of that performance is probably lost in the intake and exhuast manifolds and the fact that the cross sectional area of the stock ZS bore (1.75" diameter) is smaller than the cross sectional area of 2 HS4s (1.5" dia. each effectively 2" dia. combined).

 

[Tom Bedenbaugh]

I too don't like the MGB Stromberg set up. The air filter, water choke, and manifold drag it down. I will say though the stomberg on the TR6, and E Type work great with very little problems.

 

[mgbmedic]

thanks for all the replies, but I still don't know what I'm going to do. This is for a friends car which is a very nice, original 1977 roadster. I've used the downdraft weber and it's ok, love the twin SUs, but, like I said, it's for a friend who expects me to do all the labor, ergo, no twin SUs. I guess I'm looking for an alternative that will free up my precious time and will fix the problem. Again, thanks guys/gals, this is the best forum on the net, Bob

 

[tony barnhill]

[ QUOTE ]
it's for a friend who expects me to do all the labor

[/ QUOTE ]

So, bob, just how good of a friend is she? hehehehe

Seriously, how does she use the car? If she's just out & about on Sundays, the ZS will do what is needed once you go through it & get it reset. If everyday hard driving, you might want to look at other options.

 

[jlaird]

Tony, you have an intresting turn of mind. I like it.