I would really appreciate if someone could tell me where the engine code is stamped on a 400 or how to tell exactly what year the motor is. I am convinced that there is no such thing as an engine compartment decal or tag. Any information is greatly appreciated. Thanks in advance.

C E Webb
1979 F-150 4x4

 

One book I have says that in 1973 Ford changed from a metal tag attached to the block to a decal on the valve cover . If you have the decal you will see along the bottom a line of letters (A to M excluding I) that represent the month (A=January, etc). Below that is two rows of letters that represent the day the block was cast. The book also says that each engine has a "build-date code" cast into the block. On the 351M/400 it is on the lower right corner of the block. The code will look something like "9A12C" where the 9 is for 1979, the A is for January, and the 12 is for the 12th day. Hope this helps.

 

1st make sure you are looking at an m block. The only for sure way, to know that you are getting a 400, is to stick a small wooden dowl rod in the spark plug hole at TDC. mark the dowl. turn engine till the rod drops all the way down. mark dowl. pull dowl out. measure distance. 3.5 inch = 351m , 4 inch = 400

 

It is about a given that a 79 4X4 has a M engine.

John

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.