Questions regarding lg. to sm. journal crank spacers

[Dave Flanders]

Working with a 2.3 Ford 4 cyl Pinto engine. These come in either early large main journal or later small journal styles. Roughly a .200" diameter difference between the two. When I can't find a small journal block I use the small journal caps on a lg. block with some .020" under main bearings that are then captured by the small caps and the whole thing is line bored to use the small journal bearings.

I'm stepping up my game next year with an old 80's Ford Motorsport block (large journal) and am currently building some 8620 billet main caps for it in the small main size. In order to make myself feel better (and to make my machinist happier while line boring) I want to make the spacers out of steel so he's not cutting steel, aluminum, steel , aluminum.

Question is the actual dimensions. The way bearings kind of snap into place makes me wonder if the actual OD is slightly larger than the main bore? And if so should they finish perfectly flush at the parting line? Or does the snap come from tension in the bearing shell and do they need to be up a couple thousandths from the parting line to create some crush?

I could actually digitize a bearing shell at work but it's a royal pain for me and I'd like to understand the why's not just the how's.

And just to add - I exclusively use the later model small main journal 2.5 cranks as they're a much better piece than the stock 2.3 cranks so I'm really locked in to the spacers.

[ProPower engines]

Working with a 2.3 Ford 4 cyl Pinto engine. These come in either early large main journal or later small journal styles. Roughly a .200" diameter difference between the two. When I can't find a small journal block I use the small journal caps on a lg. block with some .020" under main bearings that are then captured by the small caps and the whole thing is line bored to use the small journal bearings.

I'm stepping up my game next year with an old 80's Ford Motorsport block (large journal) and am currently building some 8620 billet main caps for it in the small main size. In order to make myself feel better (and to make my machinist happier while line boring) I want to make the spacers out of steel so he's not cutting steel, aluminum, steel , aluminum.

Question is the actual dimensions. The way bearings kind of snap into place makes me wonder if the actual OD is slightly larger than the main bore? And if so should they finish perfectly flush at the parting line? Or does the snap come from tension in the bearing shell and do they need to be up a couple thousandths from the parting line to create some crush?

I could actually digitize a bearing shell at work but it's a royal pain for me and I'd like to understand the why's not just the how's.

And just to add - I exclusively use the later model small main journal 2.5 cranks as they're a much better piece than the stock 2.3 cranks so I'm really locked in to the spacers.

Machine some tube to suit the size needed before line boring and use counter sunk fasteners to screw them to the main saddles then bore to size.
This is how diesel blocks are repaired and is over kill yet a simple and cheap method to use a SJ. crank in a LJ block.
Just do the center bores 1st then the end bore last so alignment is not an issue depending on the line bore machines line up system
You do not need the line up tangs on the bearings anyway they just allow the installer to get them correctly located with the oil feed in the right location as they do nothing to retain the bearing in the bore.
The bearing cruse takes care of that issue. Guys over think this but most new model cars/trucks are this way.
Both for and dodge have no issues you just have to check stuff closely to be sure the bearing is located right.