Zenith-Stromberg tuning & parts

[AlamedaMGB]

First, i don't see nearly enough tech discussion on here re: carbs so I'm not sure if people don't touch them, or don't have isssue with them.

Anyway, I was tuning up my ZS so I can get me '77 MGB smogged. I went to adjust teh fine idle air mixture screw and ran into a few difficulties.
First: How do people loosen the course adjusting nut( the lock nut ) I couldn't get a wrench down in there very well, and when I put a wobble socket on there, I couldn't hold the fine idle screw. Definitely a challenge.

Second:
The fine idle adjust screw has a slot at the top, to adjust it up or down in the course adjust nut( lock nut ) but one of the tabs broke off. I hack sawed a new groove, but I would like to replace this part. Does anyone know of a source for the fine idle adjust screw? I looked in Moss, but the exploded carb view didn't show it. Only the Idle Speed adjust screw. Can I use any Set screw? Maybe one with an allen head would be better? does the profile of the trip of the screw matter?


Lastly,
I followed the Haynes process to the letter. Worked great, though a little obscure. Made more sense after I finished. And having a GasAnalyzer is vital if you are like me and can't differentiate between 'fastest smooth idle' and fastest unsmooth idle.

I still have to take it for a road test, but even if it's lean, I just need to get it to the test station.


I'm still bitter that I will be saddled with the ZS forever, as my B will never roll into smog exemption here in California. <sigh>

 

[rampant]

The part your looking for is still available from Victoria British, Telephone #!-800-255-0088 but you have to buy the whole regulator part #3-6810 $33.95 Welcome to the wonderful world of Zenieth stromburgs. Good Luck, Rick

 

[Nunyas]

welcome aboard Alameda. First you aren't permanently stuck with the ZS, if Moss Motors has it their way. Moss is supposed to start offering up a fuel injection kit for the rubber bumper 'Bs relatively soon (i.e. within the next year i think). This new fuel injection kit is supposed to be CARB certified so it would be legal to have on your MG once it becomes available.

The screw does matter. I have a '76 'B and the fine idle adjustment screw has a rubber gromet on the shaft of the screw.

At $33.95 for one of those screws it might be better to get one of those "New Old Stock" ZS carbs that I keep seeing on E-Bay. I see them all the time for about $70 plus hefty shipping (I think the seller is in the UK). Or what I ended up doing, I bought a used ZS on EBay and scavenged parts from it for the ZS that's in the car.

I haven't had much luck with the green box gas tester. I think my calibrations must be incorrect or something cause every time I've tried using mine I end up with a way rich reading or an extreme lean reading (e.g. I sometimes get -1.xx for my CO).

In the end I think i finally learned to tell in the exhaust note, but that's only good for getting into the right ball park, and then made several trips to a "pass or free retest" "Test Only" station to get it fine tuned and passed... heh

 

[AlamedaMGB]

Re: Zenith-Stromberg tuning &amp; parts

well, I'm horribly afraid of the cost of Fuel Injection.. Probably cheaper to replace all the parts every two years.. I can't imagine that a downdraft weber would have more emissions, but I could be wrong.

I'll look for a replacement, or the entire regulator.. I'm going to have to richen it up some after I get tested I'm sure.

I have half a mind to pull all the emissions crap off, and fabricate an intake to fit a common honda carb.. We'll see what the future holds..

Keep the good thoughts coming for passing Smog though.

 

[Bret]

Re: Zenith-Stromberg tuning &amp; parts

[ QUOTE ]
well, I'm horribly afraid of the cost of Fuel Injection.. Probably cheaper to replace all the parts every two years.. I can't imagine that a downdraft weber would have more emissions, but I could be wrong.

[/ QUOTE ]

While I would tend to agree that you could probably lean-out a downdraft Weber enough to pass the tail pipe smog test. But as you probably know here in the Peoples Republic of Kalifornia they do a visual inspection to make sure that all of the emissions equipment is in place and connected. This means that the Weber would never pass emissions mainly because it is not CARB certified.

The forthcoming Moss EFI kit ain’t going to be cheap with early estimated price of about $1400. But unlike any other options on the market the EFI kit “IS” smog certified & works with the all of original emissions equipment. Where this kit really shines - is that once you’ve got it in place & setup – you can basically forget it. No more headaches or wasted hours under the bonnet – tuning, tweaking & fiddling with the choke (enrichment device) before your next smog test. With the EFI - preparation for the smog test shouldn’t be any harder than any modern fuel injected engine – new plugs, filters & an oil change.

Another added benefit of the new Moss EFI kit IMHO is that it should make our late model B’s a little more reliable and easier to drive. Just hop in and go.

So I guess the real question wouldn’t be how expensive the EFI kit will be – But how much is my time worth?

 

[AlamedaMGB]

Re: Zenith-Stromberg tuning &amp; parts

Good Point BRET.

Well, I passed all the tests, except because I'm in the Bay Area, I had to run a 25MPH dyno test.. what a horrible failure. /ubbthreads/images/graemlins/cryin.gif CO% was 3X over the max so now I have to figure out why.. Guess I'll lean it out some.

FYI, while they do a functional check of the emissions components, they do NOT verify the carb make.

For 77 they check the existence of PCV, Evap controls, EGR, and Air Pump.. No specific check of the gulp valve, anti-run on valve, vacuum advance switch or fuel cut-off switch.

I agree that only the FI system will be CARB certified, but there are some ways around it.


I'm still surprised that it failed at 25mph.. Any suggestions?

 

[Bret]

Re: Zenith-Stromberg tuning &amp; parts

For what it's worth - here in San Diego we have the same rolling dyno test. I was always under the impression that the whole state had to take that test but I have been informed that some of the more rural areas don’t have to.

But just as you’ve pointed out they sometimes miss things. The last test my car went in for at the state run “smog test only” station – the guy missed a lot of stuff. Now I had everything in place and operational but when I looked over my copy of the certificate – the tech checked off that my car didn’t require a EGR valve and that my PCV valve was OK. When in fact the EGR was working fine and 78Bs don't have PVC valves. Go figure? But I kept my mouth shut and walked away happy that I'd passed the first time without any hickups.

But as temping as it might seem - my luck the first time I removed or modified something that made my vehicle none-compliant is the time I’d have a technician that’s on top of his game. Ain’t going to take that chance so I’m going with the EFI kit as soon as it is available.

As for your failure here are some suggestions:

First as painful as is sounds your going to have to regroup & start all over again with the basics. Start by checking the valve settings should be .013 if I ain’t mistaken. Anyway see what the manual says. Next I’d check for leaks in the manifold – the PO of my car tried to hide a bunch of leaks with liquid gasket. I swear I wanted to take the bonehead out in the parking lot and put 230 grains between his eyes. Anyway you can check for intake leaks with a can of carb cleaner by spraying around the various gaps between the head & the manifold and the carburetor. You might alreay know this but whatever you do - don't spray it directly into the carb - Zenith-Strombergs don't like carb cleaner!

Next I’d re-check your timing with a timing light & your idle speed with a true tachometer – do yourself a favor & don’t rely on the dash tach.

FYI - I assume you set the timing to 10BTC @ 1500RPMs. I had a guy fail me because he thought my timing was set wrong. It wasn’t – the tech just assumed it was 10 degrees BTC at idle. Seems reasonable to speculate that a tech could make a mistake in the other direction should someone set the timing at 10BTC at idle (850RPMs).

Do you know if your emissions equipment is working correctly? If you have a Bentley manual it has some pretty good tests to be sure. Also do you know if the catalytic converter is still good? I only ask because if you’ve ever seen it get cheery red (too rich) one too many times it could be toast.

Other than that follow the normal steps in tuning your car as laid out in the manual. Also you said you have a gas-analyzer – I’ve found that mine can be extremely fickle and give incorrect readings if you don’t pay attention. One bit of advice would be to run it off of an independent 12v source. But be warned one step that can really screw your readings if you don’t follow the directions in the manual. A step a lot of folks forget to do when using the gas analyzer – is to disable the air (smog) pump. If you don’t disconnect & block off the air pump as described in the manual (& your cat isn’t blown out) – you will get trashy readings and you’ll never know it until you take it in for a test.

 

[Nunyas]

Re: Zenith-Stromberg tuning &amp; parts

[ QUOTE ]
A step a lot of folks forget to do when using the gas analyzer – is to disable the air (smog) pump. If you don’t disconnect & block off the air pump as described in the manual (& your cat isn’t blown out) – you will get trashy readings and you’ll never know it until you take it in for a test.

[/ QUOTE ]

/ubbthreads/images/graemlins/eek.gif Well, I guess that's a bit of information that I didn't know when I was trying to use my gas analyzer to get the mixture dialed in. I don't recall seeing any information in my carburetor or Haynes manual that stated the CO reading was made with the smog pump disconnected. Is that in the Bently manual? /ubbthreads/images/graemlins/confused.gif

 

[Bret]

Re: Zenith-Stromberg tuning &amp; parts

[ QUOTE ]
[ QUOTE ]
A step a lot of folks forget to do when using the gas analyzer – is to disable the air (smog) pump. If you don’t disconnect & block off the air pump as described in the manual (& your cat isn’t blown out) – you will get trashy readings and you’ll never know it until you take it in for a test.

[/ QUOTE ]

/ubbthreads/images/graemlins/eek.gif Well, I guess that's a bit of information that I didn't know when I was trying to use my gas analyzer to get the mixture dialed in. I don't recall seeing any information in my carburetor or Haynes manual that stated the CO reading was made with the smog pump disconnected. Is that in the Bently manual? /ubbthreads/images/graemlins/confused.gif

[/ QUOTE ]

Yup it is in the Bentley manual for when your setting the Air/Fuel mixture. I can’t see that little step being in the Haynes SU – Zenith Stromberg manual. But it should be in the Haynes MGB manual, but I’ll look tonight when I get home.

BTW this little procedure is a good way to determine if your emissions is up to snuff and doing what it’s suppose to be doing. Next time you get the chance - try to dial in your car’s CO% reading with the pump connected and then check your reading with it removed. Likewise I always check my reading after adjusting the Air fuel mix. Makes a vast difference in the readings.

At this point it should be noted that the Haynes covers “ALL” years of MGBs in one manual. While Bentley has two manuals for the MGB that are broken down into two volumes specific to the early years (63/74) & later years (75/80). This is one of the major reasons I reach for the Bentley first and use the Haynes second as kind of a reference or second option.

 

[Nunyas]

Re: Zenith-Stromberg tuning &amp; parts

well, looks like i need to get another book to add to the library that's building up....

 

[Bret]

Re: Zenith-Stromberg tuning &amp; parts

Found it! /ubbthreads/images/graemlins/thumbsup.gif

The Haynes Manual Chapter #3, Section 32 – Carburetor, Zenith type 175 CD ST – Tuning.

Step #3 – Disconnect the air manifold-to-air pump hose at the pump, and plug it.

Not meaning to beat that dead horse again – but this goes back to my original complaint about the Haynes MGB manual. Unless you are somewhat femilure with the procedures laid out in the manual already – these short minimal almost cryptic steps can easily get confusing and overlooked.

Almost forgot there is another overlooked step to remember when tuning a stock emissions equipped Zenith Stromberg setup it the step (#4) that follows – where it tells you to remove the float chamber vent pipe from the side of the carburetor.

 

[Nunyas]

Re: Zenith-Stromberg tuning &amp; parts

wow... I remember reading that step now, but for whatever the reason, I interpretted it to mean to disconnect the smog pump from the gulp valve/intake manifold. /ubbthreads/images/graemlins/rolleyes.gif However, I DID disconnect the float chamber vent pipe... heh

maybe I need to go back and do some reading comprehension drills for a few days... heh

 

[Bret]

Re: Zenith-Stromberg tuning &amp; parts

[ QUOTE ]
wow... I remember reading that step now, but for whatever the reason, I interpretted it to mean to disconnect the smog pump from the gulp valve/intake manifold. /ubbthreads/images/graemlins/rolleyes.gif However, I DID disconnect the float chamber vent pipe... heh


[/ QUOTE ]

If it makes you feel any better /ubbthreads/images/graemlins/rolleyes.gif I thought the same thing and couldn’t figure out what I was doing wrong. But if you think about it – it makes sense because you’re still in pumping air into the cylinder chambers.
/ubbthreads/images/graemlins/thumbsup.gif

[ QUOTE ]

maybe I need to go back and do some reading comprehension drills for a few days... heh

[/ QUOTE ]

Never a bad thing /ubbthreads/images/graemlins/yesnod.gif to do a few dry runs to familiarize yourself with the procedures. IMHO it sure makes it a heck of a lot easier for when the pressure is on for an upcoming smog test.

 

[AlamedaMGB]

Re: Zenith-Stromberg tuning &amp; parts

Bret, thanks for all the tips.

This is my 4th MG, though my first ZS carb. Mechanically, the engine is running fine, valves were adjusted, timing set with a good tach, etc. There are no vacuum leaks, though that usually leads to a lean condition, not a rich CO condition like I'm seeing.

I'm guessing that adjusting the needle in the carb will do the trick. I heard a suggestion that it could be a bad float valve, but I expect I would hear the fuel pump tick every so often if that were the case..

The pass or dont' pay shop I took it too thinks they can fix it.. I figure for $60 they are welcome to try.. Then I'll bring it back home and adjust the carb..

 

[Bret]

Re: Zenith-Stromberg tuning &amp; parts

[ QUOTE ]
Bret, thanks for all the tips.

This is my 4th MG, though my first ZS carb. Mechanically, the engine is running fine, valves were adjusted, timing set with a good tach, etc. There are no vacuum leaks, though that usually leads to a lean condition, not a rich CO condition like I'm seeing.


[/ QUOTE ]

Makes sense. However the previous owner of my car had a lot of leaks around the manifold and was running real rich. Wouldn’t hardly idle below 1000RPMs! I guess that he was comfortable with the vehicle running like that. Still not sure how he ever got passed emissions testing.

[ QUOTE ]

I'm guessing that adjusting the needle in the carb will do the trick. I heard a suggestion that it could be a bad float valve, but I expect I would hear the fuel pump tick every so often if that were the case..


[/ QUOTE ]

Sounds like you got a handle on it.

[ QUOTE ]

The pass or don’t' pay shop I took it too thinks they can fix it.. I figure for $60 they are welcome to try.. Then I'll bring it back home and adjust the carb..

[/ QUOTE ]

Perhaps its just me but I’d be a little leery of such offers. Way back when I first got my B I didn’t have all the right equipment & know squat about tuning a MGB. So after two attempts I just couldn’t for the life of me get the old gal to pass smog. So giving up I took her into a “European” shop here in town. They made the same offer too and told me to leave it with them and come back the next day to pick it up. Well the next day came and I was happy to see the “PASSED” on the certificate. However when I took it out on the road it would barely make 35 MPH!

Well I purchased a manual & I spent the rest of the weekend getting it sorted out to at least go down the road under its own power. Turned out that they’d played with the valves, opening them up to about .020 and leaned the air/fuel mixture way out to the point it would hardly run. I didn’t know it at the time but along with the aforementioned manifold leaks, my catalytic converter was completely blown out at the time.

By the time the next smog test came along two years later – I’d wisely used the money I would have paid someone else to do it for me and purchased all the tools & equipment to properly tune my B on my own.

Good luck,
/ubbthreads/images/graemlins/thumbsup.gif

 

[AlamedaMGB]

Re: Zenith-Stromberg tuning &amp;amp; parts

Yeah, I'll try anything once. I know why your care wouldn't make it past 35.. They leaned it out so it would pass..

Anyway, I left my needle adjusting tool and my haynes guide for them. I figured they could adjust the carb and put it on the meter, and go back and forth.. This they did, but still didn't get it into the right range.. Shop owner thinks it might be a bad converter, which would make sense if it's been running rich.

Didn't charge me a dime. How's that grab you.. Don't find that often.

Anyway, I'm going to try the 'lean it out until it won't run' trick, and see if she passes. Then I'll replace the cat and test it again. Sigh.

Anyone put old flanges on a universal catalytic converter?

 

[Mack]

Re: Zenith-Stromberg tuning &amp; parts

Alameda, Welcome, I'm rather new myself, but I have been working on MG's myself for about five years, first a '77 midget and now a '76B. The part you are looking for, is it the brass needle inside the plastic nut? If so, drop me a note at jmack43@verizon.net, I've collected a few carbs for parts from people I've met here in upstate NY who have been very nice to try and help me out, I'll continue the helpfulness and send you the part if that is what you need, of coarse no gurantees if it is any good or not, but what the heck, it's worth a try. Good luck, MACK /ubbthreads/images/graemlins/cheers.gif

 

[AlamedaMGB]

Re: Zenith-Stromberg tuning &amp; parts

[ QUOTE ]

The part you are looking for, is it the brass needle inside the plastic nut?

[/ QUOTE ]

Thanks Mack. The screw I'm looking for is the air bleed screw on the OTHER side of the carb, over by the idle adjust.. It's fine right now, with my hacksaw fix, but if I get back to the carb for repairs, I'll replace it.

 

[AlamedaMGB]

Important Safety Tip

DON'T DRINK A GUINNESS AND ATTEMPT TO WORK ON YOUR STROMBERG.

I was looking at the wrong side, talking about the locknut idle speed adjustment screw.. Turns out it's just a screw. Got a new stainless screw to use..

Ran across something interesting though, Stainless screws are not very tough.. managed to strip it on one portion of threads trying to use the lock nut on it. I think I'll stick with hardened pieces from now on..

Thanks for the input all.. I got a NOS stromberg on the way from GB.. $120 after shipping.

And I smogged with flying colors!

YEAH!!!

 

[Bret]

Re: Important Safety Tip

Congrats on the emissions pass! /ubbthreads/images/graemlins/thumbsup.gif

As for drinking beer while working on the car (or is that the other way around)? /ubbthreads/images/graemlins/rolleyes.gif Well, I must admit to having done so on a number of occasions. But I drink domestic (light beer) and save the good (Guinness & New Castle etc.) stuff for my more serious beer drinking.

However I am safe in that I save the test drive for the next morning.

/ubbthreads/images/graemlins/cheers.gif