[S10Gary]

I understand the early 2.8 engins like in my 85 had small journals and had a tendency to break like mine did. Later engines I think starting in 87 or 88 had large journals and this problem was corrected. I still have the block of the original 2.8 can it be converted to a large journal? I could keep my mechanical fuel pump then as 3.4 does not have a place for a mechanical pump.

 

[oldeerslayer]

Be easier and a lot less expensive to install a newer block and a simple external electric low pressure fuel pump. They can be had for as little as $10. Not saying I'd use that one. Brand names run $50-75.
The difference in main journal size is 0.153543". Having your block line bored that much won't be cheap. Plus you'll need a new $300 crankshaft. More money than most 85 S10's are worth. There could be an with rods unless they remained the same size. Not sure how timing chain would work. Or which one you'd use. Gonna get expensive real quick

 

[S10Gary]

well I guess I will get rid of this block then. The engine in the truck now is a 2.8 with no provision for a manual fuel pump so I dont know what year it is or if it has a small or large journal. Maybe that will be alright with a good electric pump. The original block with fuel pump is on a stand in my garage. I guess I will get rid of it then. Should I save the original 85 heads, pistons, and intake? Are there any other carbs that fit on the original 1985 manifold?

 

[The_Raven]

The switch to large journal was in 1985.5. But as above if yours is small journal, it's just much cheaper and easier to add in an electric pump near the fuel tank.

The switch between external balance and internal balance was in 1987 or 1988, depending on what source you use.

Any block that doesn't have provision for a mechanical fuel pump will be large journal, since that change happened after the switch to large journal.

I'm not sure what the 3.4 has to do with the conversation, but if you were thinking you could swap 3.4 internals into a 2.8 block and have a 3.4, that won't work. The crank itself will swap into a large journal block, since the crank is shared with the 3.1 (3.31" stroke). But the bore of the 3.4 is larger.
The 2.8 and 3.1 share the same bore, 3.503"
The 2.8 stroke is 2.99"
The 3.1 and 3.4 stroke is 3.31"
The bore of the 3.4 is 3.62"

So you can swap a 3.1/3.4 crank into a 2.8 block, along with 3.1 pistons and have a 3.1, if you wanted. I did this many years ago, when I built my "Franken60" that also utilized FWD aluminum heads and intake.

Timing chains are interchangeable between small and large journal cranks. Rod journal sizing didn't change until the 3500 (LX9) was introduced in 2006. The large and small journal reference is to the main journal size.

 

[S10Gary]

Thanks for the reply Raven. Looking at my first post I see what you mean about the reference to the 3.4. I probably was thinking that I cant have a 3.4 with a mechanical pump, but is it possible to have a large journal 2.8 with a mechanical pump? There is an engine in the truck now, I honestly dont know if it runs. I was told its a 2.8 and there was an edelbrock electric fuel pump inline that was rigged up at one point. Ive since removed all the rigged up stuff on this truck and Im starting over. I guess I have to go with an electric pump. What year did the mechanical pump go away.

 

[The_Raven]

1986 was the first year of EFI and the block mounted fuel pump provision also went away.

I don't know for sure, but the 1985.5 block used up to the introduction of the 1986 model year should be large journal with mechanical fuel pump provisions, however, finding one of these blocks will likely be difficult, and running an electric pump is easy to do.

 

[S10Gary]

Ok thanks. Is there a way to identify a 1985.5 2.8? without tearing it open and measuring the journals?

 

[The_Raven]

Ok thanks. Is there a way to identify a 1985.5 2.8? without tearing it open and measuring the journals?

Not that I'm aware of.

 

[PeteD]

well I guess I will get rid of this block then. The engine in the truck now is a 2.8 with no provision for a manual fuel pump so I dont know what year it is or if it has a small or large journal. Maybe that will be alright with a good electric pump. The original block with fuel pump is on a stand in my garage. I guess I will get rid of it then. Should I save the original 85 heads, pistons, and intake? Are there any other carbs that fit on the original 1985 manifold?

Put them on eBay

 

[jimmykicker]

1986 was the first year of EFI and the block mounted fuel pump provision also went away.

I don't know for sure, but the 1985.5 block used up to the introduction of the 1986 model year should be large journal with mechanical fuel pump provisions, however, finding one of these blocks will likely be difficult, and running an electric pump is easy to do.

Pretty sure there were some leftover 85 blocks in 86 trucks with block off plates. I saw one like that in the junkyard. The plate could have been put there, but I'm fairly certain it was stock.