Passing AirCare (Emissions)

Article written by Skye Nott. Published on 2006-04-02
MG Experience Library – Service:Carburetors and Fuel Section
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This section contains tips and tricks for those of us unlucky enough to live in areas that have emissions testing and do not have exemptions for vintage vehicles.

To pass emissions, the first thing you have to do is have a car in good tune. That means clean & gap the spark plugs, adjust the valves, check the dwell of the points, check or replace the rotor, cap and plug wires, and make sure the timing is correct. Next move over to the carbs, and tune them to spec. A common cause of failure is air leaks in the carbs; this usually resolved by fitting oversized throttle shafts. Last, check the exhaust system for holes and that the bolts and clamps are in good order.

A whole topic unto itself is the emissions equipment fitted to later MGBs. I've got a 66 myself, which only has a PCV valve, so I'm not too experienced with air pumps, gulp valves, etc etc. If someone would like to write an article detailing those systems, I'd be grateful.

Here's some readings from my car (1966 MGB) over the years. Unfortunately a lot of my old records were stolen along with some spares out of the trunk of my car a while back, but I'll add new test results here as they come.

Date	HC (ppm)				CO (%)				NOx (ppm)		Result
	Driving		Idle		Driving		Idle		Driving
	Read	Max	Read	Max	Read	Max	Read	Max	Read	Max
01-APR-2000	147	500	747	1500	1.91	6.00	2.33	7.50	1988	?	PASS
01-APR-2000	Comments: This is just after I got the carbs rebuilt (the usual throttle shaft bushing wear) and tuned the car up to spec.
10-OCT-2001	224	409	2000	1044	5.12	3.96	8.93	5.48	1013	4356	FAIL
10-OCT-2001	Comments: Didn't tune up the car this time and here's the obvious result. This is just after I had a dropped valve fixed in the engine. Also notice the new AirCare II max readings are a LOT lower than they used to be!
30-JUN-1994	180	500	187	600	2.63	3.50	1.72	6.00	1096	3433	PASS
30-JUN-1994	Comments: Just for comparison, here's what my 1.3L '81 Honda Civic read back in 1994. I guess they have a point about new cars being a lot more efficient. I don't think it even had a cat, and it certainly didn't have EFI.

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~ Passing AirCare (Emissions) ~

Article by Skye Nott – Published 2006-04-02

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