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MG MGA - Catalytic Converters

I am currently doing some work for the MG Car Club, trawling archived Safety Fast magazines to extract technical articles for their website.

I have just come across an article from 1999 showing bolt-on catalytic converters that can be fitted to carburated cars, such as the MGA. The product in the article was/is made by USA company Agriemach.

Just wondering if anyone has ever fitted one or a similar type and what has been the result.

Steve Gyles

I have not seen this before but my Google search shows it as a West Sussex company. You should be best situated to get more info than we in the USA.
Chuck Schaefer


I stand corrected. Yes, it's an English company distributing an American product.

Steve Gyles

Steve. Her in Arizona, specifically in Maricopa and Pima counties, annual emissions inspections are required of all cars made after 1966. On my two 79 MGBs, the carbs were changed out for Weber DGVs, requiring a different exhaust system and some other form of cat than the factory style. I had a local muffler shop install in line cats into both cars and have had no trouble passing the emissions testing with them. However, my daughter's 77B does not have a cat on it and it too has passed the required inspections over the years. However, my cars have shown lower unburned hydrocarbons (HC) than hers. However, the amount was rather slight and, again, her car meets the tailpipe standards without the use of a cat. A well tuned engine seems to be as important as a cat. All of these cars were in regular use with the 77 and one of my 79s being our daily drivers. I suspect that regular use and proper maintenance are more important that the add on emissions items.

Les Bengtson


The MGCC expert who commented on the article came to the same conclusion as you, saying that "The more efficient your engine, the less work these convertors have to do"

This was the article as written in 1999:

The HF range of catalytic converters from North America for cleaning exhaust emissions - new to the UK vehicle aftermarket - are highly competitive and now available exclusively from engine accessory specialists Agriemach (01342 713743). Truly universal and fully proven, the units with their unique dual in-line catalyst substrates act as a purifier to ensure effective contaminant reduction from exhaust emissions. They protect the environment by using oxygen to convert poisonous carbon monoxide and hydrocarbons into harmless carbon dioxide and water. Skilful internal engineering combines maximum exhaust flow with minimal back pressure assisting engine power and fuel economy. The HF range has been developed to suit most makes of cars, vans , and light commercial vehicles up to 5.9 litres powered by unleaded petrol, and cover exhaust inlet bullet sizes from 1.5" to 3". The purifier's body shell and end cones are manufactured from 100% stainless steel for long life and supplied with full 5 year 50,000 mile manufacturer's warranty. A dual-purpose external heat shield also provides protection against accidental body shell damage from stones and flying debris . Compact and easily installed or modified for direct fit, the catalytic purifiers are approved by both the US Environmental Protection Agency, and by the world's most stringent regulatory body, the California Air Resources Board. Agriemach has considerable experience of catalytic converters. For many years they have been successfully supplying exhaust purifiers used with diesel and LPG powered engines on public service vehicles , on heavy plant, and on load handling equipment.

APW Writes:

On enquiry I have ascertained that these catalytic converters can be fitted to all our M.G.s, not withstanding a lack of electronics and fuelled through carburettors. The more efficient your engine, the less work these convertors have to do. They also burn off all unburnt fuel from the engine, including Benzene. For that reason alone they could be recommended fitting with the coming of unleaded petrol and the increase in Benzene (a Carcinogen) in the atmosphere that will result. One cannot foresee Mrs Bloggins in her old metro fitting these, so it's responsible users of old cars who will probably be allowed to use them in the future, at least at a lower cost, once the legislations rule that we must fit them or pay much more road tax.


Steve Gyles

This thread was discussed on 15/10/2010

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