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MG MGB Technical - Spectacular emissions failure.

I just put my first late model B through its Missouri emissions test.

HC was 3402 PPM, limit is 600 PPM
CO was 9%, limit is 6%

Now, is fitting a smog pump, currently missing from the car, and repairing the sticking Stromberg auto-choke likely to improve the emissions enough to pass or am I also going to have to take care of the blue cloud of burning oil constantly hanging around the rear of the car?

I'm hoping I won't have to mess with the worn rings and bores yet but if the consensus is that it is necessary I will start putting together the spare engine sitting in the garage.

The next series of questions will be on how to modify a 1967 high compression engine so it will also pass the test!
The Wiz

I'll have my emissions equipment sitting out for you.

Robert
Robert Rushing

Wiz. With those CO and HC readings, you have a very rich mixture. Switching to a manual choke and playing with the available needles might be a good idea. Personally, since we can run the Weber DGV carbs now, I no longer even think about tuning the Z-S carb.

Yes, an air pump will lower the numbers, but not as much as you need them lowered. Is the cat functional? With the numbers you are allowed, my 68 with its old, worn HC engine would pass. Les
Les Bengtson

Wiz,
You might try disabling the vacuum advance to pass the test.
mike parker

The Colourtune is in the box now too.

Robert
Robert Rushing

Les - The Miz says she doesn't like you right now - she wanted a nice easy fix! :-)

I am going to fit the smog pump, I will also weaken the mixture as far as possible, make sure the choke is off for the next test and also disconnect the vacuum advance per mike's suggestion to see how low i can get the numbers.

Thanks Robert! I shall fit those parts this weekend and put her through the test again. For those not in the know, I get unlimited free retests for the next 30 days so i am sure that in that time I can find the one trick necessary to make the car pass.

The one thing the car did pass on was the visual check of the emissions equipment - sans smog pump and with an obviously mangled PCV valve. I think the supervisor was so embarrassed at her ignorance of the car (she had to ask me to pop the bonnet and she also wanted to know if an MG was a "General Motors or something" so she could find it in her book) that she refused to admit that she couldn't recognise an MG cat, smog pump etc. that she just gave it a pass on that part of the test!
The Wiz

I was supposed to get my emissions tested this month, but I got a nice sweet letter in the mail from the state saying that the new law was passed allowing all cars made before 1978 to be no longer required to get tested!

All thanks to one guy - Terry Fanning in our local MG Club - who wrote and wrote and wrote letters until he found a state senator who took up the cause.

And who says one man can't make a difference?

Robert

Robert Rushing

According to the emissions people today that law hasn't come into effect yet - I guess that is another thing they know nothing about!

Why didn't he make it 1980 and older to cover all MGs? :-)
The Wiz

Forgot to mention Les, the cat is hollow, The Miz made sure she blew the guts out of it 19 years ago to gain an extra few HP!
The Wiz

Wiz. Good luck. You are going to need it. But, I suspect that if you get the carb dialed in, you should be able to pass the requirement with no problem. Cannot find the last inspection paperwork on my 79B, but have it on my 77 Scout and 80 Bronco.
For the 77 (V-8 with dual exhaust and no cat) the standards are 350 PPM HC and 4.0% CO. For the 80 (300-6 with a cat) the standards are 220 ppm HC and 1.2% CO. Be glad you live in St. Louis. Les
Les Bengtson

My tuned car in good condition no cat and SUs would breeze through that. Get the carbs tuned and the ingition spot on , new airfilters etc and good luck
S Best

Wiz, you're right! It doesn't take effect until August 28th. My letter said if I get the car licensed after the 28th (and before the 31st) I won't have to get an emissions inspection.

I may have to wait in a long line, but I'm looking forward to it!

Don't ask me why they picked 1978 instead of 1980. Originally, Missouri broke it down to 71-80 had to have tail pipe tests while 81-OBDC1 cars had to get a dynamic test on a rolling road. New OBDC2 cars just have a computer plugged into them with no running test.

Why start at 71? Why cut-off at 78? It's a mystery wrapped in an engma along with a big fat envelope full of cash I'm sure.

Robert
Robert Rushing

Agreed you probably need to tune up your car. You can get an additional decrease in emissions if you retard the ignition timing several degrees. This is why American cars started using ported vacuum advance in the late 70's.
Matt Kulka

Matt,
Didn't the ported vacuum give more advance at idle for emissions?
Steve Postins

In NYC, we've had the rolling road for a couple of years, but word is they may do away with it due to shops damaging customers cars while on "the rack".

The car is subjected to a lot of stress without the benefit of airflow. Trannys and overheated engines are a regular problem.

Regards,

Brian C
Brian Corrigan

Ugh, don't put the air pump back on unless you think the next visual inspection will be more stringent. It won't do a whit of good without the cat functioning as it's purpose was to inject air for the cat to work on.

Stromberg (shudder). Repair, replace or disable the choke so the extra fuel can't get into the engine and I suspect you will pass.
Hint #1 tune carb to "lean" side of proper running.
Set ignition to proper spec.
You didn't say what the Nox limit was and how close you were to that. Leaner mixtures burn hotter and, while lowering CO and HC, cause higher Nox.

Visible smoke from tailpipe would fail a test in most states and it is probably pressing the HC way up the scale. You may not be able to pass while it smokes.

Sounds to me like you need to finish that other motor!

Mike!
mike!

A few other pointers. Test the car warmed up. Also, use an ethanol additive to boost the octane and lower the emissions. The ZS carb is a terrible device-- they often leaked fuel onto the hot cat, causing a nice fire. All my emission troubles went away when I put in a weber. But if you must use the ZS, eliminate all air and fuel leaks.
Ira Spector

Fresh engine oil immediately before the test helps a bit.
David

Robert,

Thanks for the info on the emissions law. I had been trying to follow it since Terry mentioned it at a club meeting, but had not seen anything on it lately. I may be able to turn in my historic tags for regular plates now.

If I remember correctly, the law was to eliminate from the emissions testing requirement, all cars that would otherwise qualify for registration as historic vehicles in Missouri (25 years old or older). When I do the math, I get 1979, but I guess the state gets 1978.

I just need to get the engine back in my '72 B and get on the road.

Greg

Update.

I have spent the last few days working on the car, I've fitted a smog pump, new air rail and a new PCV valve. The plumbing took some sorting out to get it all right again but it all seems to be doing what it should now.

I did a compression check to try and locate the cause of the hefty oil consumption, dry readings were 135 to 145 psi, not too bad for a 78,000 mile engine, wet, with a little oil, the readings were consistently 10 psi higher, not a huge problem IMO. However, while checking the gauge reading on one occasion I heard the distinctive metallic "snap" of a valve snapping closed! I have a sticking valve on the engine! (Number 3 cylinder judging by the sooty plug). That possibly explains the oil consumption (I'm guessing the valve stem seals are shot and the oil is pouring through the jammed valve) but I was puzzled as the car seems to be running too well to have a serious valve problem.

Then I checked the ignition timing - 35° advance at tickover! Reset that to a total advance of 32° which gives about 8° at tickover. Now the car has a definite missfire and backfire - the sticking valve is showing itself. it seems DPO just cranked the advance as far forward as he could to disguise the missfire problem.

Tomorrow I take the valve cover off to see what is under there and I am hoping I can fix whatever it is without pulling the head. I have successfully freed stuck valves on an engine that has sat for a while without pulling the head before so I am hoping I can do that again - then Tuesday it is back to the testing station to see how much I have improved things.

If the worse comes to the worse we have decided that we could just park the car until December 31st when it will be old enough to no longer need an emissions test then get the tags then. However - I want to drive it so I am going to do everything I possibly can to get the car through the test!
The Wiz

Register it in another state!

The last time I had to pass my '77 (years ago, as they have now abandoned the effort for inspections), I had to almost shut down one SU, run the other real lean, install a cheap cat, and retard the ignition. The car barely ran, made it up the inspection ramp, passed the test (barely) and I chuffed away.....


.....around the corner whereupon I balanced the carbs and timed the ignition. The cat had to stay, tho.

A man's gotta do what a man's gotta do - John Wayne
Loogie

--------------------She passed!----------------------

On the standard Stromberg with no tweaks outside the normal running settings, ignition timing is as it should be, mixture is as it should be, cat is hollow but she passed!

HC was 400ppm, limit is 600ppm, the first test the reading was 3402ppm. CO was 5.99%, limit is 6%, the reading was 9% on the first test.

Now I can pull the air pump and all related crap back off because as of December she will no longer need emissions tests because of her age!
The Wiz

I did the HappyDance in the emissions waiting area. Trust me - that's not a good thing to witness. LOL!

TheMiz

If the problem is during the Dyno part of the test you might try going in with fresh hi test gas but not a full tank. Remove everything from the trunk including the spare and incease tire presure to 35 or above. This will decrease rolling resistance and the engine will be under less load requiring less fuel. I've also seen after market fuel additives sold for purpose of passing smog. Just a thought.
Bob Ekstrand

This thread was discussed between 06/08/2004 and 14/08/2004

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