All RPi engine options have, as standard, additional specification improvements upon O/E specification. Further upgrade options are readily available.

The following information regarding O/E engine specs and capacity is for those who have asked, as well as for those who did not ask but feel they need to know.

• 3.5 = 89.5mm bore Std 3.5 crank
• 3.9 = 94mm bore Std 3.5 stroke crank
• 4.2 = 94mm (3.9 bore ) plus and 4.2 longer stroke crank
• 4.0 is the same capacity as 3.9 but uses later big journal crank and is cross bolted
• 4.6 + 94mm bore ( As per - 3.9 and 4.0) but uses later big journal (long stroke) crank and is also cross bolted as is the 4.0.

Stage 1 and Stage 3 as above.