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MG MGA - Stub Stacks - The 18/80 Shows Us The Way

How history repeats itself. I am still working on archive material for the MGCC and came across this article from the Vintage Register in which an 18/80 owner 'discovered' the stub stack. He has out-done us in making his version in brass! Interesting to note that his analysis completely validates my own initial experiences, including better fuel consumption.

"I have been playing around for some time with different ideas for improving the airflow to the carburettors on the 18/80. If you look at the intakes they are very sharp edged and less than ideal for smooth flow. I had some ready-made flanges 'in stock' from a more modern car and these were fitted as a trial. I noticed immediately that the engine seemed to rev more freely and set about designing a special bell mouth adaptor to fit directly onto the intake tube of each carburettor.
The photograph shows the bell mouth inlet I designed to fit over the carburettor inlet tube and I turned two of these on my lathe from a solid piece of brass to give a smooth transition into the intake diameter.

I have completed about 4000 miles this year with the bell mouths fitted and have found a marked improvement in all-round engine performance. The most obvious change is the ease with which the engine exceeds 3000 RPM in all gears but there has also been a very useful reduction in fuel consumption. The average fuel consumption has reduced from 20 to 23.5 MPG with the bell mouths and I attribute this to better breathing of the engine at cruising speed.

Vintage Register comment: So John, better revving and better fuel consumption. I am surprised that the mod has such an amazing effect, considering the long inlet tract on these engines, but with trial results like that I think I had better find myself a piece of brass for my carbs."

Steve



Steve Gyles

Some of his commentary on the effect are almost identical to yours. When was the article written?
I also like his term ' bell mouth' much more than the ugly stub stack term ..latter may apply to the overdone protrusions that stick out from some carbs ( and performance wise do no better than the bell mouths) but for the low profile entry radius units we are using the term is inappropriate.
longing to try them out on my beastie....the other Steve did a great job organizing it all ...
Neil Ferguson

This thread was discussed between 20/01/2012 and 21/01/2012

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.