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MG MGB Technical - Needles for SU AUD 52

Does anyone know what needles are right for the AUD 52 F carburetters on my ´63 MGB? Some sources say No. 5, one say MB. Standard air filters.

Tore
Tore

I see now that the Moss online catalogue says MB, so I guess that is he right one.

Tore
Tore

Tore-
For the AUD 52 specification SU HS4 carburetor #6 is the rich needle, MB is the standard needle, #21 is the lean needle.
Steve S.

Thanks for valuable information, Steve.

Tore
Tore

Tore-
Glad to help. Incidentally, the #5 needle that was recommended to you was the standard needle for the 1 1/2" SU HS4 specification AUD 135 caburetor that was used on the 18GA and 18GB engines (1964-1967). That is the only difference between the carburetor specifications as both the AUD 52 and the AUD 135 used the same jets (AUD 9141 Front, AUD 9142 Rear) and plain throttle discs (WZX 1323). The ports are the same (Head Casting # 906). Your high compression 18G engine and the 18GA and 18GB high compression engines also both used the same spark curve (Lucas Distributor # 40897) and the same camshaft (Original Equipment BMC Part # 88G 303) which had identical timing. I suspect the the change of fuel metering needle was necessitated by the changes in the crankcase breathing system involved in switching over to a closed system, but I'm a bit hazy as to just exactly why.
Steve S.

This thread was discussed between 17/05/2008 and 18/05/2008

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