how do i find out which engine i have !!

stupid question i know but how do i find out which engine i have in my 2.3 1988 volvo 240 i.e the b23a or b230 etc.and can you tell by your engine number if the engine has been replaced?

Although normally very useful in this situation, I believe that the VIN as recorded on the vehicle will only be good for information about the original fittings. The engine number should be a separate entry on the V5 document. You could check that against the number on the engine in the car to see if there has been any change (how many of us remember to advise DVLA if we change the engine).

B230 or B23 

It is cast into the block when it is manufactured, B230 or B23, you will find it on the right hand side of the engine below and to the rear of the oil filter, near the exhaust front pipe. The whole of the Vin No will also tell you as stated by adamsky01.

The engine type and number should be etched into the engine on the inlet side at the top. Highlighted here..... (just visible in this pic) You might need a toothbrush and some cleaner to see it clearly. Failing that post up a pic of it here and we can have a look.