Volvo Repair: Volvo S40 Engine Replacement, variable valve timing, volvo dealership

Question
Mr. TenBrook,
Hello, I am in serious need of some expert advice.  My friend had a Volvo 2001 S40 which the rear main went and he proceeded to drive the vehicle until the computer shut the car down.  He took it to the Volvo dealership and they informed him his engine was shot.  My father owns a rental company, so I thought I could just drop another engine in the car and it would be all set to go.  We put it on the hoist and took out the original engine and took a closer look at it.  The rear main was fried, as was the main bearings.  We purchased another engine from a junk yard which came out of a car which was totaled.  Here is our problem.  The junk yard told us the engine was a 2000 S40, but it would work in our 2001 S40.  After we installed it and turned it over, it is misfiring like there's no tomorrow.  Also, the catalytic converter before the flex pipe overheated and put so much heat on the flex pipe leading into the first muffler it turned it BRIGHT orange.  Also, I noticed on the timing belt covers two different numbers.  On the 2001 engine cover I noticed a number of B4204T2, and the cover of the 2000 engine it says B4204T3.  Are these compatible engines, and what can you suggest we do to get this car running?  

Sincerely,
Mike  

Answer
Well the motors are NOT compatible.  The 2000 had variable valve timing systems different from the 2001-2003.  The 2004's were unique to themselves in that system.  They were all different systems.  2000 was a very unique year for S40's.  All the hardware and wiring were pretty different.  I would try getting the correct motor or preferably a 2002 if no match is found.  The bright hot cat is probably the work of the misfires.  Try checking out the plugs and coils especially because they always fail and cause terrible misfires ESPECIALLY when accelerating.

James