Stock 94 Cherokee motor with around 230K. Had compression issues and a cracked head. When I tore down the motor and removed the main caps the bearing looked like new. Crank is smooth and polish-able as-is so before I ordered the re-ring kit, I decided I should probably measure the crank and main journals just to be sure.

The rods are fine and match what I'm seeing are the correct diameter.
But the mains are a different story. I'm finding this as the spec:
"Main bearing journal diameter. No.1 thru 6. 2.4996 to 2.5001 inches. No.7. 2.4980 to 2.4995 inches."
All mine measure 2.4960 - which puts them at between .0036 and .0041 for #1-6 and .002 and .0035 for #7
Since the main bearings looked nearly new - I decided to Plastigaige them all and they we're all had around .002 clearance.
There is no indication this motor was ever rebuilt, but if it were, I'd expect to find .010 or more delta from the spec.

Any ideas?

 

I think the spec you've come across is for the V8.

 

I'm getting my specs here: http://www.cherokeetalk.com/forum/f2...cations-34650/
Halfway down the page.
I've checked in other places too and they jive with this.

 

what's the diameter of your main journals?

 

All mine 1-6 measure 2.4960
I grabbed one of the old bearing shells to se if there were any markings on the back
One side of the shell half has 3-4 then below that F 85 - then the other side of that half has A 3

 

I'd find a factory service manual.

I think you're fine.

 

Thanks, I'll hunt one down or run to the Chrysler stealer here in town.
Based on what the 230k bearings looked like - nearly new, minor imperfections, no sign of copper - whatever size they were I'm sure would be fine, but I see some posts where it said that the factory sometimes made adjustments to at the final assembly stage so my concern is that an off-the-shelf "standard" bearing won't fit.

I'm also trying to find someone with a large enough micrometer for the 2.5" diameter journal. I measured mine with calipers - several times - but they were calipers and I understand they are the NOT best for round surfaces.

Writing all this, I'm thinking I need to measure my calipers throat depth...if it's less than 1.25" then I may be accurately measuring my journals - just not at the TRUE diameter.

 

The FSM for my 97 shows the same, for the 4.0L.

Main bearing journal diameter:
No.1 thru 6. 2.4996 to 2.5001 inches.
No.7. 2.4980 to 2.4995 inches.

 

So it seems my 1.5" throat calipers are deep enough to measure a 2.5" journal.


I've decided to order the .001 under size and see what the plastigauge says.
Thanks everyone.