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MG MGB GT V8 Factory Originals Technical - Best Needles for HIF6 carbs

Hi again all. Some time ago someone on this board commented that a richer needle than the standard BBU was needed for an engine with K & N filters (as I have). On investigating why my engine "hunts" a little (almost imperceptible)when maintaining any given speed I find that a PO has fitted BBW needles. On comparing the profiles I find that they vary quite a bit with the BBW being richer. Have I got the right needles or would it be useful to change them? If so what is a good place to start.

Ian Thomson
ian thomson

From my comparison program I can't find a needle that is richer than the BBW right across the range. There are a couple with a richer top half but either a weaker or much the same bottom half. I have K&Ns and fitted BAKs which helped, but my symptom was 'bogging-down' when opening the throttle slightly, it maintained a given speed smoothly. Maybe you have another problem like a vacuum leak.
Paul Hunt

Thanks Paul. Looking at your needle comparison chart (great site by the way) I see that your choice falls between the standard needle and the one I am using. Does anyone else have any thoughts. What are the others using?
ian thomson

I think I was that someone asking for the right needle. I have contacted a Dutch compagny ( BCCP fuelsystems) who are specialised in rebuilding carbs and supplying parts and the lady on the phone convinced me to go for the standard BAK needle.
I have installed them together with new gasvalve disc's and new shaft seals and after readjusting the carbs i think it runs very good now.



Mine is 3.5, 10.5/1 comp, tubular block hugger stainless headers and a copy of the factory airbox with after market filters. It was dyno'd and the best across the range needles fitted. They are not standard but I need to wait for the weekend before I check the actual letters on them. Your air filter system does make a difference to what is the best needle.
Ian G Buckley

Further to my last post above. The needle is BBZ.
Ian G Buckley

Thanks Ian, Arno, Paul. Any more?
ian thomson

Rolling road trial is the only sure way to find out.

This thread was discussed between 02/07/2002 and 08/07/2002

MG MGB GT V8 Factory Originals Technical index

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