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MG MGB Technical - Failed Emission again this year.

Last year I struggled to get my '79B to pass. I was given lots of usefull info at that time. This year I failed again. The things I did last year were Timing 10 degrees BTDC, adjust valve clearances, changed to a leaner metering needle (45H), new points and plugs(NKG)Fresh oil. Luckily, the parts man at a local britsh car shop allowed me to put the car on their exhaust gas testing machine so I could tweek the distributer and Carb adjustments, I was able to get it within specs and drive right over to the testing facility. That was a relief.

Although the car is a '79 the engine is a '75. I have all the smog equipment attached. The Cat is probably just a shell. So my three questions are. Would there be a substantial reduction in emissions if I put a new cat converter on, and if so does this reduce both the CO and HC readings (Both are currently above the limits). Secondly, would it be worthwhile to replace the ZS carb with a new one(a rather expensive proposition). Other then opening up the carb last year to replace the metering needle, It was 6 years ago that I rebuilt the carb using the standard kit. I have another carb kit that I bought last year, I was going to use before finally passing. Finally, since I don't have an exhaust gas tester available. It would be hit or miss with my adjustments. I notice that JC Whitney has what they call a professional quality tester available for under $200. Does anybody have knowledge as to the accuarcy of this device.
As always, any advice would be much appreciated.
John
John F

I would try the following, having struggled with the same
problems in CA.

1. Definitely get the CO tester (gunson's) Adjust CO to
5.5 % with air pump disconnected, air rail plugged, float
bowl vent line unplugged. Works for me, although I've had
problems with this device going out of adjustment after a year
or so.

2. Get a new Cat converter -- this will dramatically lower
HC, but have a lesser effect on CO.

3. Make sure your smog pump is working, if not, CO will be
way too high.

4. It wouldn't hurt to clean out the carb, but I doubt this is
causing the emissions failure. If the autochoke is stuck, you
may be too rich which would cause very high CO.

5. There may be an altitude problem since you're in Denver.
Moss catalog lists a 45 M needle for high altitude applications.

6. Is the camshaft stock? Performance cams have too large
valve overlap at idle to pass smog easily. See www.mgbmga.com
for info on CA smog which may be useful also.

Good luck, and I'm sure others will have useful suggestions.
Ronald

Thanks for the suggestions Ron.
I'm a little confused about your suggestion #1. My car needs to be below 2% CO to pass here in Denver. The air rail and pump need to be there also to pass the visual inspection. So do you mean I should disconnect and plug those items, adjust the carb and timing to get the reading down to 5.5% CO, then I should reconnect the air rail and pump and bowl vent and the reading will then be down towards where I need it to be?

Suggestion #2 is now done, I ordered a new cat from VB.
Is the Gunson's color tune also helpful to have?

Sug #3. How does one really know if the air pump is operating correctly. It turns freely and is almost brand new,less then 1000 miles of use.

#4. I converted to a manuel choke years ago. Is there anything I need to watch for in that case? The car starts much faster since the conversion to manuel as opposed to the old auto choke.

#5. I will double check (now that you mention it) It may well have been a 45M I put in last fall not the 45H.

#6 I have never changed the cam, As far as I know it is stock. I really don't have any history on the car prior to my owning it. I do know the engine is not the orignal. From it's odd ball engine ID #. The block casting date indcates it is 1975. Some have suggested, (from the ID#) that it may be either a factory
replacement engine, or possibly from an Austin Marina or even a Massey Ferguson tractor engine.

Three more years and I can apply for collector series plates which will exempt me from the E-test. Just have to pass one time when applying and then never again as long as you maintain the collector tags. I never plan to sell the car BTW.
Cheers,
John.

John F

John, as to CO, yes it is set to 5.5% with the smog pump
disconnected. After reconnecting the smog pump, you will see
that the CO falls dramatically (should be below 1%.)

With the smog pump disconnected, and the engine running,
you can feel if air is coming out of the pump.

I haven't found the colortune helpful -- its just not accurate enough
for emission-controlled carbs.

If the throttle lever is against the slow idle screw with the
choke off, then the choke is probably working correctly. The only
way it could still be enriching the carb is if the choke metering
needle o-ring was bad, or somehow disconnected from the
internal choke cam lever.
Ronald

John. Like Ron, I am having problems with my Gunson's CO meter. It is reading in negative numbers and will not read positive. Have e-mailed Gunson twice but they do not bother to respond. Hence, I too will be looking for another source of instrument. The procedure that Ron outlines is the factory procedure for setting the emissions. The 5.0-5.5% with the equipment removed is supposed to equate to less than 2.0% with the pollution equipment re-attached. I have always tuned with all of the polution control equipment attached and tuned to standards required. Most people I know use this method rather than the factory method. CO and HC readings are related, but the relationship varies with mixture strength. Rich mixture gives higher CO and may give higher HC. Lean mixture gives lower CO and, due to a lean misfire, may give higher HC. Thus, while a new cat may not lower the CO, it may allow you to tune somewhat more finely and still pass both the CO and HC portions of the test. For testing, refer to the factory workshop manual for the exact procedure. Most of us do not have all of the equipment and gauges required and, if there is a question, refer it to a professional (after making sure that he has the proper equipment). Les
Les Bengtson

Back when I was fixing cars for the LA airport using airport transfers tunbridge wells police dept. , they decided we had to lead the way by smogging our old beat to s**t cruisers (!) I got a smog license and made them (and many other cars) pass by plugging the AIR pump and adjustijg the CO whilst keeping a weather eye on the HC meter - what you do is , lean out the CO untill the HC begins to rise , then you fatten up the CO untill the HC bottoms out at it's lowest reading . now re-connect the AIR pump and it _should_ sail right through the test . of course when any BMC engine has the usual wobbly valve guides it might need that rectified first but that's how I did it .

It should be able to run nice & clean with 2.0% CO at about 400 PPM HC - Cal. has tightened up the limits since then but I believe it'll pass and run O.K. at those measurements .

Most of the home CO meters go out of spec. in a few months , NAPA sells test gas to use for adjustment .

-Nate
Nate

One thing that seems to be missing from all these emission related issues is one of the type of use the car has had befoe it is subject to emission tests.

Since the introduction of cats and other emission related issues the failure rate of even newer cars has rocketted. The usual tweaks and set ups have been done and the situation is improved, often to a degree that gets a car through.

However one thing that so many forget is that when it comes to exhaust gas testting you are not just going to be reading the emission from the engines combustion at the time of the test, but also residual emission deposits that are lodged in the exhaust system. In addition I will also include combustion depositis that are found within the cylinder head, and even build up in piston ring grooves.

The build up of deposits is slow and continuous and is usually accelerated by gentle and infrequent use. Most of u know how much better our cars (of whatever age) run after a good run of many miles and this principle cvabn be adapted to assist in achieving emission compliance.

One of the most effective ways I see here of getting cars through our emission test, which in fairness is easy on the older cars, so is used mainly on the newer ones, is to give the car a damn good thrashing where the whole of the rev range is used and this is done for at least 10 miles. In cases of very speed restricted roads then some compensation can be made by usuing a lower gear to rasie the revs with short periods of brake application so that full throttle and full laod can be imposed for a few seconds at a time.

One really choked engines this hard use really does sometimes give a chimney sweep effect out of the exhaust. Additionally the extra loading on the engine tends to move hardened deposits, which can be improved upon by use of a petrol treatment. Freeing rings provides for better cylinder seal and less oil to dilute the mixture and polute the exhaust. Removed depositis in the engine provides for smoother airflow and better cylinder filling and better mixture distribution for better combustion.

Finally if you engine won't take use within the original intended window of perfromance then isn't it time to do the appropraite work that will allow such use?

A 'good blast' is a real leveller and I have seen this work so many times here, that it must be worth doing elsewhere too.

Rog
Roger Parker

Thank you both Ron and Les,
As I recall both of you responded to my post last year when I was having the same problem. I really want to avoid taking the car to a professional if at all possible, I rarely take any vehicles in. I lost the free acesss that I had to the exhaust gas analyzer last year at one of the local britsh car shops. I called another britsh shop. They will help me if I bring the car in and let them work on it. If it comes to this I would like to at least have done everthing I can to get it close to passing, so all they would have to do is put it on the analyzer and fine tune it if necessary. One of the things I like about these older cars is I can do, and enjoy doing most of the work myself, and it is always a learning experience. It would be a fairly easy task, to pass the emission test if I just had a decent exhaust analyzer. Just can't justify paying 3 to 4 thousand for one of those machines. I can't even find one for rent anywhere. So I am hoping this one I've ordered from JC Whitney will do the trick. I am not sure if it is a Gunson's or not.
I will keep you posted. In the mean time, if anyone has any other suggestions or comments please post them.
John, From the Mile High City.
John F

Ron does this look like it is the Gunson's exhaust gas tester?
http://www.jcwhitney.com/product.jhtml?CATID=35066&BQ=jcw2
John F

That link didn't quite take you there try this one.
http://www.jcwhitney.com/catsubpic.jhtml?CATID=3295&BQ=jcw2
John

I give up on the link, however copy and paste does work.
John F

Yep, that's the Gunson's gastester.

One thing, be careful not to rev the engine with the gastester
connected to the exhaust. This can blow out the pump in the
tester. I managed to break my last gastester this way.
Ronald

Ronald. Did you get yours repaired or just buy a new one. My is one of the newer model, digital ones which has gone out after three years of use (about a dozen tunes on my cars). I probably should not complain as this is less than $20 per use, but the local mechanics will set the Weber equipped cars for $40 using a proper four gas analyzer. If you got yours repaired, where did you have the work done? I pulled the cover off my meter and everything is solid state. Hence, not being an electronics tech, I do not know how it could start reading negative numbers only. Thanks, Les
Les Bengtson

Les,
I bought a new Gastester, since my broken
one was out of warranty.

Gunson's in the UK does offer a repair service
(not sure of the URL, but its easy to find.) But
I think it would be pretty expensive to ship the
broken one from the US and back again, and maybe
have to pay duty.

I think having a mechanic adjust the carb is a good
idea, except most of them around here freak out
at the sight of a British car.
Ronald

Hi,

Maybe "thinking out of the box" could be of some help to you. Here in WA state my car is now exempt from the test (it is over the age limit of 25 years)you would think that they would test the old cars and exempt the new computer controlled ones, but I guess the real game is revenue enhancement, more newer cars than old ones. Anyway I used to take the test WITHOUT air filters (less resistance more air and leaner charge-SU's are a constant depression style of carb) also I have heard that with an almost empty tank a strong solution of alchol/gas will get it to sail through. Just be sure to fill up with gas after test.Years ago I have heard about a guy who would get your car through through the test by putting the license plates and vinstrip of a car,on another car that has already recently passed,take the test and swap back. I have just heard about these remedies and would never do them myself nor would I recommend anyone else doing same.
Alan

Ronald. Thanks. I have contacted Gunson's twice through their site with no response. Guess I will have to buy another one. Wish I could find one from a company that care about after sale service though.

Alan. Here in Arizona, there are no exemptions. Every car, from 67 on, must be tested. The emissions test is cruise and idle on a dyanmometer. That is immediately followed by an equipment inspection. If any equipment, including air cleaners, is missing, you fail the entire test. Then, you have to take a full retest after having the equipment repaired. As to using an alcohol mixture in the tank, we do that all the time. We have "oxygenated" fuel which contains either alcohol or MBTE (MTBE?) for the entire year. Great fun. Go to the gas station and get a buzz on. Les
Les Bengtson

I feel sorry for you guys. Here in Pa. if you drive your car less than 5000 miles per year it is automatically exempt from emissions testing but they still get $10 from you for the exempt sticker(paperwork). Once you get to be 25 years old you can get an Antique tag that also exempts you from the annual inspection. The state figures that if you keep it as antique then you do the work to maintain it in running condition. One thing I always did before testing is change the oil and filter. My 75b passed even with the smog gear removed but I don't think our limits are as strict as out west.
Ed

We do have the exemption from the e-test here in Colorado once the car turns 25 years(three more years and I can get them). However you must apply for special Collector series tags, which are renewed every 5 years, and you do need to pass an intial e-test at the time you apply. Thereafter as long as you maintain those special plates there is never any further emissions tests required. I'm keeping my fingers crossed that they don't change that law before I get to apply for my Collector tags.

As far as the Alcohol gas. It is mandatory here in Denver in the fall and winter months only. I think it is about 10% ehthenol. I am wondering how high a concentration of alcohol you can burn. Would adding additional alcohol to my gas help?
John
John F

Funny you should ask John.

I went through this process last year on our 1970. Only had to pass one time, but failed the first two times I tried. Failed miserably in fact. I was told by both test stations to get a valve job and rebuild the carburetors!
Instead I went on the advice of a friend and ran the tank to near empty. I then added a couple gallons of gas/alcohol at a ratio of approximately 50/50. The car ran pretty bad, and struggled to hold a steady idle. But it passed. By a wide margin too. I think I was more surprised than the emissions tester!
I drove it home and disconnected the fuel hose at the carburetor and let the fuel pump empty the tank into a container. Refilled with fresh gas, and drove to Boulder to pick up my collector tags. Ahh, no more testing!
By the way, I got the methanol from Shoco oil Co in Commerce City. They sell it in five gallon buckets. I'm sure there are other places to buy it near you.

Scott
Scott Wooley

Thanks Scott, I will give that a try along with all the other tips I've received. Did you make it out to the English Car Conclave last month. I think I may have met you there one year. Check out my web page about the conclave. http://www.angelfire.com/co3/79mgb
John F

John, I'm in Arvada. Give me an E-Mail at GJurata@ix.netcom.com include your phone number. We'll get you to pass. It's Sunday morn. about 9:00 A.M.
Victor Gardino

Has anyone ever taken off there Catalytic converter with out removing the Exhaust/intake manifold, that third bolt (the one closet to the block) sure is tough to get at, now I know why I kept that half inch open end/box wrench that broke in half a while back. I've had that cat off before but this is the first time I removed it, whilst leaving the manifold in place. Sure teaches you the meaning of patience.

I've also got the carb on the workbench and will rebulid it and check the needle during the week. New cat shoud be arriving in the mail soon. I also put in the Champion RN12YC plugs today. Thanks again to all who have given suggestions. This BBS is a great resource. I will let the group know as soon as I pass.
John
John F

Doug Jackson talks about passing smog test on his site at mgbmga.com.
Mike Hayworth

This thread was discussed between 25/10/2001 and 29/10/2001

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