This distributor advance curve showing how many degrees the spark is advanced across the engine rev range for the 41610 distributor fitted to the UK rubber bumpers.
Click the link below for other distributors for other years of the MGB.
I set my timing not to the book but using a vacuum gauge which produced the best results at about 30deg at tickover which with a 15deg weights advance at 4000rpm (about 80mph the max I do) is way too much.
They say around 35deg advance max or you could damage the engine.
I finally set it at 20deg and still had a nice even tickover with no misses.
I’m wondering if the 41610 dizzy is the best for my motor which has had some engine mods by previous owners. I might try to test it with the 25D dizzy.