Calculations for determining the primary and secondary exhaust pipe diameter and lengths, you will need to know the Camshaft specs and desired RPM, In particular the opening and closing events of the exhaust valve. In simple terms the inside diameter of the pipe relates to regulating the exhaust gas flow potential and the length relates to controlling the effect of reversion waves.

If money, time and effort are plentiful, then stepped headers could be something to look into. However saying that, stepped headers have less of an effect on collector lengths under 26 inchs.

From my calculations based on my camshaft timing event in my race engine. @ 50thou Opens Bbdc 58 and closes Atdc 23.5. the apparent ideal collector length for max power at 6000 rpm is 30.8 inches. My race engine is tuned to deliver peak power at 8000 rpm and has a collector length of 22.3 inches.

For your application, its probably easier to buy a set off the shelf as they are made to fit the B110 straight off the bat. Ebay US had a few from memory, if you are unable to find some local to you. My vote goes for set with 38mm primaries for the inside diameter.

here is a link to the headers made in the US on fleabay.

A-series headers



cheers