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MG MGB Technical - Fuel Stabilizer & Smog Check

Hi,

I have 1977 MGB, and am using fuel stabilizer along with premium unleaded gas.

I brought the car in for a pre-inspection last weekend, and we did not get beyond the exhaust CO analyzing point ..... max carbon monoxide for 1977 car is 0.7% - mine measured 6.4%.

Is it possible the fuel stabilizer is causing the high emissions?

Can the fule stabilizer cause harm to the cat. converter?

Thanks,
Greg
Greg Knodel

Hard to say. I'm assuming you're using fuel stabilizer because the fuel's old (I don't remember having to store an MG in the winter in CA!). Anyhow, old fuel probably doesn't help (assuming it's not burning as well, it's likely producing higher CO levels). Get the old fuel out, then you'd probably do well to try leaning out your mixture on the ZS (that will take you CO levels down...not too lean, as it may adversely effect your HC levels). ALSO, ensure you have a working air pump, then remove your air injection rails, then clean out both the rails AND the air injection ports on the head. As I recall, I used a pipe cleaner on the rails and a 1/8" drill bit (WITHOUT the drill) to punch out the crud on the air injection ports. Plug the other ports and you'll know you have cleared the port of interest because it'll make a nice "snapping" sound when idling (I can't remember the exact size of the bolts required to plug the holes (it's been a while...7/16" fine {e.g. 20 tpi?} thread?), but it's all over the archives). When you have good amounts of air being injected into your exhaust ports AND you've leaned out the mixture, your CO levels will drop (we're down to simple math here...no magic). If you can manage to do this in conjunction with slightly retarding the timing...better. Then, if you can increase your valve clearances by a few thousanths (Doug Jackson recommends up to 25 thou for the test, but I think this is a bit extreme), it'll reduce your valve overlap and decrease your CO even more.

I passed CA smog once with a BONE empty catalytic converter...it can be done (I passed the "hard" CA Smog II test on the threadmill). Most emissions equipment of this vintage is simply ridiculous. It's all about restricting what you take in, burning the crap out of it, then injecting air in the exhaust valves to dilute the exhaust resulting in fewer PPM (how do you think SUV's pass?). What a bunch of crap! The cat converter just creates enough heat to burn most of what's left (after horribly restricting your breathing...which in a stock configuration has more than it's share of problems to begin with).

Hope this helps,

Barry
Barry Kindig

If you do as Barry suggests you should be fine with the emissions. I don't think opening the points will help, but may be detrimental. One additional detail. If you have the 'catalytic convertor' then you should adjust the carburettor 'rich'. This provides extra fuel to burn in the convertor and make it nice and hot. Check the sticker under the hood. I think it is 5.5% CO with the air pump disconnected. This is richer than a normal carburettor tune for power (~3.5%). Last, adjust the idle as high as the test will allow.

With the suggestions that Barry gave, a freshly rebuilt carb (new needle) and setting the carburetter to the %CO spec on the sticker, I've gotten .41% CO and 36PPM HC on a '77.
Werner

Hi,

Thanks for your feedback.

I use fuel stabilizer because I don't drive the car enough, and I understand the stabilizer will help prevent the varnish build up in the fuel lines, carb. and so on.

I'm driving more now to empty the tank, then I will refill with fresh gas, and check it out with my Smog tester at home, before attmpting another pre-inspection.

Thanks again.

Greg
Greg Knodel

Barry-

Pls. give additional details ----> what exactly are the "air injection rails" and where are they located?

On the carb, intake manifold, head?

Thanks,
Greg
Greg Knodel

Some refer to this setup as the air injection manifold...the pipes that run from your air/smog pump to the cylinder head (entering near the spark plugs on special drilled castings...four entrances). There's a check valve between the pump and this set of pipes, thus ensuring that air only flows one way. This check valve should be replaced in addition to cleaning the air injection rails/manifold.
Barry Kindig

Barry,

The air injection rails and the inlet ports were really clogged with carbon ..... had to use a bit more than a pipe cleaner to get it clean all the way through. I ended up using the center of a control cable, to inch my way through, and finsished with carb. cleaner to get it good and clean. The 1/8" drill bit worked great fot the inlet ports.

I have one of the smog testers - I'll hook it up today, and see how much the (air injector cleaning) alone helps the CO level.

If needed, I can also adjust the valve clearences and retard the timing a bit to finish the job. Will keep you posted on my success in dealing with the state of California, and their smog laws.

Thanks for your help!

Greg
Greg Knodel

It may sound crazy, but I had an old ford truck and never changed the oil in it as it was only used occasionally to pick up parts. Failed emmisions poorly and after an oil change it passed with flying colors. Sounds strange, but if you have not put fresh oil in a long time you may want to give it a try.
J Arthurs

Greg,

I'm looking forward to hearing how your numbers changed. This made a significant difference when I performed the same action on my '76 about 3 years ago...with a little careful tuning, I passed with an empty catalytic converter.

Barry
Barry Kindig

Here's a wild idea, but one that really happened to me, and maybe a useful one to folks who are trying to smog an MG for the first time. Remove the air injection rail and make sure you can blow air through it. Sometime in my '68 MGB's past, someone tapped the ID on the check valve, and inserted a threaded plug. Invisible until you removed the check valve from the rail. I could've rodded out the ports until the bovines came home, and still not gotten any air into the exhaust manifold.

Back in the late 60's, a lot of stoopid high school boys thought that plugging the air injection would get you free horsepower. Of course, they still left the belt on the smog pump. A classic case of a little bit of knowledge being a dangerous thing.
Terrence Goodell

This thread was discussed between 17/06/2002 and 26/06/2002

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