390 engine year

[bigdawg]

What is the best way to identify what year a 390 engine is other than by the valve cover tag. Thanks Bigdawg

[donsjave]

By the year, the only other way that I have found is by looking at the crank. Most but not all crank will have the year marked on the rear most crank throws on either the front or rear as you are looking at the crank. It should start with the year that the crank was made followed by the part number that AMC used for that particular year. Sorry, but you must take the engine apart to see what year the engine could have possilbly been built.

[304_dude]

Hi,

From what I heard the 390 did not get large numbers cast on the side until 1970... 68 and 69 had no marking or small numbers. If you are not familiar with differentiating large and small numbers, you may post a clean pic on this thread for help.

Oh, all 390 cranks fit 390 engines, so if by chance you drop the pan you can identify a 70 390 by the wide webbing at the mains. I only say this, since you are not the original owner... who knows what has been done to the engine in its lifetime.

[bigdawg]

Hi,

I am trying to prove that I have 1970 Heads on my 390 with out taking anything apart. Someone told me that 1970 dog leg heads have 7/16 bolts. If that is true a 5/8 socket would fit on them. This holds is true on my heads. Do you know if 1969 and earlier heads have 9/16 heads on their 3/8 bolts?

Thanks
Bigdawg

[donsjave]

I hink that there is another way to determine if you have 70 heads or not. In the 70 model they went to the "dogleg" intake ports while still using the log type exhaust openings. Not until the 71 model years did AMC convert over to the dogleg exhaust manifolds.
There is also the casting numbers that are on the heads beneath the valve covers. I believe that the casting numbers can be found listed else where within this web site.
AMC converted to what I believe was 1/2 bolts for their heads starting with the 70 model year engine. I could be wrong here but like most things, it should be (the information) found within this web site.
It should be noted that the 70 model year heads are the most desirable of all of the heads that are out there for they have smaller combustion chambers than the others. Smaller combustion chambers will deliver more compression and thus more power.

[a440plus6®]

70 390s have half inch bolts with 5/8 heads.