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MG MGB GT V8 Factory Originals Technical - difference between 03an and 04an brake fittings?

Working on a 67 MGB-GT with V8 conversion. Has a '67 type single stage master cylinder. Looking to replace the standard steel brake line between the master cylinder and the proportioning valve with a flexible braided stainless steel hose (make it easier to work on master cylinder). Trying to mail order the part and I'm not familiar with the "an" type fittings. The threads on the steel line we are replacing are 3/8"-24 (NF) threads- does anyone know how that relates to a 03an or 04an fitting types- and which one would be appropriate for this application?

Thanks for your help.

jason uhley

My experience is that the threads on -3 and -4 AN fittings are the same, only the inner bore is different. -3 fittings are for 3/16" ID line and -4 fittings are for 1/4" ID line. I personally like the -4 size as it means less internal line restriction when retracting the brakes or clutch, thus quicker action. I found that -4 AN male to male unions worked fine as adaptors directly to my brake switch and to the clutch master cylinder on my midget.
Bill Young

You have got to be careful here...

Dash 3 is for brakes and Dash 4 is suitable for the clutch.It is true that fliud flow is more important with the larger displacement during clutch travel-this is not true in the braking system as a greater cross ectional area must lead to more fluid compressibility for a given pipe run. Remember that AN fittings use a 37 deg cone angle and that SAE fittings are 45 deg. You may get away with graunching up a 37 deg fitting into a soft brass SAE fitting but this trick won't work where the components are steel.
Earl's do adapters(male to male/female to female et al)to convert from the 37 deg to 45deg.


John Bourke
John Bourke

This thread was discussed between 27/05/2001 and 30/05/2001

MG MGB GT V8 Factory Originals Technical index

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