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MG MGB Technical - Speedograph vs Standard Air Filters

Hi all

A while ago I fitted a pair of speedograph air filters to my '73 roadster, and havent noticed any difference in sound or performance (if anything, the sound appears to have become a little more 'wimpy'). Should I be expecting a difference? Thinking about it, the filters in the standard unit are a lot larger and so in theory suck more air in, upping the performance. Am I right? Just want to know if I should just quit while behind and slap the old ones back on.
Sorry, a bit of a 'going nowhere' subject, but i'd be interested to know what you think.
Cheers

Mike
M Rees

Mike,
You might want to take a look at this site, http://www.hotelling.com/mgb7.htm for an alternative filter setup and also for a bit of info on what is necessary for any carb/filter installation to work properly. Perhaps Steve S. of Virginia will pick up here too as I believe he has a good discussion of the dynamics of air filters/air flow as it applies in this case.

You will note that it is not just depth of the filter (how far it stands beyond the mouth of the carb) but also that an proper airhorn/stub stack is used to smooth the flow of air into the carb. Without that airhorn, a bit of turbulence around the edges of the mouth of the carb will be generated and that will generate more noise and screw up the air flow into the venturi.
Bob Muenchausen

Mike;

Hate to tell you this, but your best option is probably to throw away the Speedographs and replace them with either the original filter cans (using K&N elements) or with Bob's very unique and cost effective air filter set-up. K&N makes replacement air filter elements for the standard MG air filter and they significantly improve air flow to the carbs.

If you read "How to Power Tune the MGB Engine" you will find out that the Speedograph filters are considered a down grade in that they don't flow as much air as even the original factory filters and that they also remove the factory filter mount plate which had a fairly effective stub-stack that directed air flow to the carburetor. In a nutshell, the racing gurus consider pancake style filters to be junk as far as increasing engine performance goes.

If you do replace the factory style filter elements with K&N filter elements, you should check the fuel/air mixture as you will now have more air flowing to the engine and may have to richen up the mixture a bit.
Ron Kluwe

Cheers for your help guys!
Just as I suspected, the speedographs are crap, oh well, at least they looked pretty for a while! Might give Bob's idea a go. I'll let you know how I get on.
Thanks again
M Rees

This thread was discussed between 19/02/2004 and 20/02/2004

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