So all I would need to do is change the crank on my M20 325i to that from an Eta engine and this would increase the stroke some 15%? Would I need to make any other mods to accomadate the new crank in the 325i engine? Maybe the headgasket?

I take it putting the fast road cam on this new set-up should be OK too?

How much BHP/Torque gain would I see if I just changed the crank to a 2.7 eta one on my engine?

Forgive my ignorance on some of these matters!

Thanks.

How would I go about boring out my 2.5i engine into a 2.7i engine?

My car is in the garage at the moment as one iof the valves is bent. I plan on getting a performance cam and chip, but would also like to bore it out to 2.7 to hit the 200
+bhp mark. What would I need to take into consideration, and what other BMW's could I source parts from? I live in the UK.

Thanks.

The more popular method of increasing displacement on the M20 engine is stroking, not boring. The max bore is about 86mm (stock 84mm). However going from a 2.5 crank to 2.7 increases the stroke some 15%, and this will also increase displacement. Metric Mechanics 2.9 liters have 86mm bore w/2.7 liter cranks. Be aware that with the increased bore size you will have to modify the head gasket.