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MG MGB GT V8 Factory Originals Technical - SU needle advice
|I'm using a standard Rover 3500 SD1 engine in my MGB V8 with twin SU HIF6 carbs(FZX 1270)and high flow sport air filters.|
According to the Rover 3500 Haynes manual the carbs should have BAK needles.
Can anyone give me an advice for the best needle type to try for this configuration, the mixture seems to be to poor now.
|Arno, I have a SU reference catalogue and it shows BBU|
(CUD 1142) needle MBGGT 1973 with HIF6 carbs.
Steve @Mini Mania
|In what way is the mixture bad? Whatever needles you have (within reason) you should be able to get a good idle mixture. Then you have to decide if the mixture is weak or rich and at what throttle openings i.e. needle position. If it is bogging-down and pulling the choke makes a significant improvement then you know it was weak. Judging the needle position is more difficult. There are some needle selection programs around whereby you can compare a range of needles with your existing needle and select one that has a thinner (for weak) profile at the required needle position.|
See http://www.geocities.com/scottbeavis/winsu/winsu.html for a Windows program or http://www.team.net/www/morgan/tech/tuning.html for a DOS version.
Or there are lists of needles in both name and size order at http://www.mgb-stuff.org.uk and click on 'Spanners' and 'SU Needles'.
A BAK has a steadily richer profile than a BBU from about 1/4 throttle.
This thread was discussed between 28/05/2002 and 29/05/2002
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.