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MG MGB Technical - Foam air filters involves carburettor adjustment

Hello,

On a B 1976, I noticed Since air filter has been replaced for a foam type the engine does't behave well at low RPM. Playing with manual choke could help. I imagine free flow filter allows air more easily to carb. It like carb's mixture. is too weak.

Thaks for your input.

JGC
Jean Guy Catford

Actually, if the foam air filter restricts air flow and the choke helps, then the mixture is too strong. The stock paper element is usually a better performer than any foam replacement.
Jeff Schlemmer

If you need the choke generally it's lean.
Mike MaGee

I would get out the colourtune, I do know that some people on this board would not. You can try the pin lifting method if you have SUs fitted.
S Best

Sorry. Mike's right. I hadn't had my coffee yet!
Jeff Schlemmer

Yes you can expect it to be too weak. If there's a rich needle for your card you could try that. What carb(s) do you have? Rich.

Rich

Hi,

It is a Stromberg with a fun to adjust needle.

Cheers,

JGC
P.S.I am surprise that only an air filter change could modIfy so much fuel/air ratio.
Jean Guy Catford

I doubt the air cleaners are the problem. Even a dirty air cleaner will not make a difference at low rpms as air flow is directly correlated with increasing rpms. (Doubling the rpm does not double the air flow as the engine becomes a less effecient air pump as rpms increase.) for example, an engine at low rpms - 2000 rpms - draws approx 1/2 the airflow at full throttle, than at 4000 rpm.

A restricted or dirty air cleaner makes itself felt as rpms and air flow increase. At part throttle, the difference from a dirty or restrictive air filter is even less.

Have you checked you float height settings, your jet centering, and idle mixture adjustment?

With a smog controlled 76 you probably have a vacuum retard that retards the spark as you give it throttle. Check your ignition timing and vacuum advance system.
Barry

Barry Parkinson

This thread was discussed between 05/06/2005 and 06/06/2005

MG MGB Technical index

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