The B20A and Honda's B Series

The 3rd gen Accord and 2nd gen Prelude's B20A Are not related to the rest of the Honda B Series Family, Although they do share a few things in common:

 - The JDM B20A's Bore is 81mm, Same as the B16A and most other Honda B Series motors. You can use the higher compression pistons from a VTEC b series engine, But you have to bore the wrist pin hole out to 22mm on the b series pistons and shave some material where the rod goes [More Info]

- You can easily Modify the Intake manifold from a later B series (B16A & B18C) VTEC Intake manifold to fit the B20A, The lower Intake manifold bolts line up and three holes need to be drilled in the flange for the top bolts [More Info].

 - Non VTEC Honda Motors like the B18A1, B18B, B20B/B20Z share the same rocker cover and camshafts. You can use a non vtec Distributor from one of these motors on a B20A also with little modification [More Info]. VTEC B Series camshafts, Rocker covers and distributors do not fit whatsoever.

 - You can upgrade your B20A to use B series Adjustable cam gears, By using the cambelt crank gear and water pump from a B20A5 3rd Gen Prelude Engine and the cam belt from a H23A. [More Info]

However the Head gasket layout is somewhat different and therefore you cannot use B series heads on the B20A. Gearboxes also do not fit, Bellhousing bolt up patterns are completely different which is why you can only use gearboxes from the 3rd generation accord and 2nd generation prelude.

There was Another B20A made for the 1987-1991 3rd Generation Prelude, It came out SOHC Twin Carb (B20A3) and DOHC PGM-FI (B20A5) and leans back towards the firewall. It shares the same Bore and Stroke as the B20A and the rocker cover is simular, But the Head Gasket layout and intake manifold Bolt patterns are different and not compatible. Bell housing bolt up pattern is also different again so gearboxes will not swap.