I'm on with building a Nasp 5 cylinder Focus RS / ST / Volvo engine at the moment and I'm wondering what is the best route to take regarding stroke.


I will use the 83mm block and bore it to 84mm as I have two of these in my garage awaiting attention.

Problem is do I use the 77mm stroke crank and go for a high reving (9500rpm) engine?

Or do I use the 90mm stroke and go for a more torquey engine that may produce more power?

The BTCC Volvos produced over 300bhp out of the 2 litre 5 cylinder using a 83mm bore and 73mm stroke

The good thing about the 77mm stroke route is the extra revs and the good rod length of 152mm giving a rod ratio of 2

It will give a capacity of just over 2.1

The bad thing about the 90mm stroke is the lower rev limit and the rod length of 140mm which gives a bad rod ratio of 1.5

What do you guys suggest I should do?

Head will be reworked using larger valves with smaller stems, hydraulic tappets will be replaced for solids and I already have the throttle bodies and manifold sorted for a 10 injector setup which was developed for a touring car team in Belgium.

Also have sourced some cam blanks for some wild profile cams too.


Cheers

Austen