Higher Compression or bigger bore

[NigelC]

Both have their advantages and can deliver more power but in different ways at different parts of the power band for a Nord 1962 cc engine. Be happy to hear opinions or comments.

[MD]

The Nord engine is well proven unit that has always been in general terms a detuned racing engine for road use. Taking that up several notches in naturally aspirated form takes some considerable grey matter. It will always be limited by only two valves, hemi chamber, and wet liners that either migrate or split under extremes of duress.

Nevertheless for a naturally aspirated engine, I am of the opinion that you can increase the bore (within reason) and increase compression to get the maximum combustion efficiency on a specific fuel. The biggest obstacle for high compression is the octane rating of pump fuel.

[NigelC]

Thank you! I am going for 85mm bore and 11.5 compression.