engine advice

[sajid1]

can someone clarify this for me please as much info as possible



are the bottom ends on a 320 and 325i the same

can a 325i head be put on a 320 bottom end?

if i look at a 325i head, just near the heat shield there is usually a stamp saying 2.5/2.7 or just 2.5, is that to mark the head as 2.5 or the bottom end as 2.5


and will there me much difference is performance??

what about compression?? etc etc

reason being that i know someone who bought a 325i sport and there saying it didnt pull as much as it should, they thought it needs a service, but having stripped the engine down to check the cams etc, everything was fine, they think the car has a 320 engine or bottom end in it, but the head i.e top clearly states 2.5

also where exactly is the engine number located on the block??

will the dealers be able to determine the engine cc from the engine number

[Brianmoooore]

Bottom ends of a 320 and 325 are NOT the same.
320 has a bore of 80mm and a stroke of 66mm, 325 has ba bore of 84mm and a stroke of 75mm.
The heads are not interchangeable as the two engines have dfferent shaped piston tops and different shaped combustion chambers in the heads.
Performance wise, the extra 500cc of the 2.5 makes a massive difference, and it sounds like your friend has bought a car with an engine downgrade.
Engine number on most BMW engines is on the block just above the sump, just past half way back on the left hand side.

[e30bmlover]

performance wise there is no comparison......... 320i 129bhp 325i 171bhp as for the engine numbers the 325i is m20b25 and the 320 is m20b20.

[sajid1]

so if the head has a stamp saying 2.5 just near the heat shield then it is a 2.5 engine isnt it??

because he rang up Sytner and Rydale with the engine number on the log book and the engine number off the engine and he was told that just from the engine number nothing can be determined i.e they cant tell what cc it is and what it came out off, they need the chassis number etc

also the engine number he has are different from the one above the engine number on the logbook is 250114486??

[Brianmoooore]

Chassis number means absolutely nothing if the engine has been changed.
IIRC, the first two digits of the engine number are the capacity. 2 litre engine would start 20.

[sajid1]

so can anyone tell me please-- if there is stamp i.e circle with 2.5 engraved, just above the heat shield in the usual place on the right of the engine that clearly reads 2.5 then is it a 2.5 engine is it not??