82 brat

hey i just bought an 82 brat and it came with a second engine the guy i bought it from saud that it was a 2.0 and tha the one in it was either 1.9 or 1.8. is there any way to be able to find out what type of engine it is.also the engine that is in the car is having some probs, 1st it backfires(sounds like shotgun blast) after 2mins. of run time,2nd it has no power the trans is fine but i think either timing is off or bad vacuum line. any advise would be helpful thanks.

btw one of the engines has a hitachi carb and one has a C-W type carb hope that helps