So, does this 1977 Pontiac Can Am have a 403 or a 400? According to Wikipedia of the 1,377 Can Am's made there are only 42 on the Can Am Registry with a 403. Comparing pictures of the motor in question with other 403's and 400's it seems that the oil filler pipe is in the right place to be a 403, but I don't know too much about these cars.