What Defines a 4.1 Production Block

[REDS HOT AIR]

my factory 85 ttype block is that way 20 bolt and has 3.8 and 4.1 on the back .. I was going to sonic test it but never got around to it

 

[Daniel Jost]

Ok so it is thought to be a 85 block then, can this be made into 4.1? I thought the 4.1 was to the bottom right but i guess im wrong... I still haven't checked my other parts matching block that is sittting around from my 6/85 grand national 20 bolt pan. oh that block is stamped 84 to, ill have pics tonight