I am looking at a 1963 wildcat convertible and the owner says the engine code is "4JI5685" I can't find this code and I was wondering if anyone knows anything about it.

Jim,

That looks like the serial # from the drivers side of the block. It only tells us the year, assembly plant and the series # of the car, and there should be two more digits. J designates it as a 63 If the digit after J is a 1 and not an I, it was built in Flint, MI.

The engine production codes are on the same surface on the passenger side of the engine. There will be a two-letter code followed by a three number date code. The letter code designates the year and engine type. Again, J is for 63 followed by an R for the 2 bbl 401, a T for a 4 bbl 401 and a W for the 4 bbl 425.