I have an 85 2.8 I just pulled out of my 86 GT, I need to know how you can tell the difference between the two 85 blocks gm used.
I know the only difference is in the size of the main bearing journals.

The two part numbers for the different main bearings are here.

1st design: MS1494P 63.3mm journal
2nd design: MS2037A

I dont know what size the main journals are for the late style block casting, all I know is that the late 85-88 2.8's used the second style main journal size.

I need to know how to ID the block so I know which journal size it has.
are there any casting number differences?

Measure the journals.?

okay, looking at the block its casting # is 14091820
I see at the bottom of the first picture a note as to which crank casting numbers are for which journals.

1st design has the 504 cast number only.
2nd design is 817, 245 and 85...

I just went into the shop and checked the crank, its an 817 cast. YAY! (phew)

thank you!

The journal has everything to do with the crankshaft and nothing to do with the block then, right?

and also, the only other difference is the size of the oil galleys.

If your rebuilding you will be measuring all the journals both crank and block anyway,right?
It is showing different crank numbers as well so likely to be both different diameter,if I understand what your asking.
Better galleys or smaller ?
You gonna build something fun ?

[This message has been edited by DefEddie (edited 01-28-2013).]

I was just wondering so I can use the correct bearings with the crankshaft.
I already have a built 2.8 sitting here but im changing out the crank for a steel one from eagle.

EDIT: upon more detailed reading the 817 crank is used for all year v6's exept the 88.
so if anything that means the bearings are different where they make contact on the block,
meaning it was the block that changed, not the crank, and the bearings make up the difference.

Also the earlier model 2.8's use smaller oil galleys which had proved to be the 60* v6's achillies heel...

[This message has been edited by AL87 (edited 01-29-2013).]