806 D MAIN BEARINGS

I'm doing in frame oHaul. 806d 361 cu in engine. Standard mains standard rod bearings sizes. Standard size came out. When I start to tighten main caps it gets very hard to rotate the crankshaft. Caps are in correct order, and clean and properly seated.

It acts like there is an undersized bearing installed, you tighten and it stops crank from moving. No pistons are installed, just the mains.
What should I check next?

Tractor vet will be along to enlighten you.
Warning he may be a little harsh.

Look at your old bearings, see if they
show spots that have copper showing. You
might have core shift going on. The
bearings can wear out slowly as the main
bearing tunnel shifts. When new bearings
get put in it can lock it up.

that is because you might be installing under size brgs which are thicker. have you checked this out? look on back of new brgs. to see if this is true. giving lodgical solution as I don't know if they turn those diesel cranks.

Hello Cowboy welcome to YT! You may have the
bearings caps in order front to rear, but are you
installing them in the correct orientation as they were
originally. Generally the bearing locating tabs are
located on the same side for assembly. As in two
bearing cap bolts, both tabs near the same bolt. I also agree about the possibility that you were mistakenly given under size bearings. Need to verify bearing shell thickness old to new. A bearing ball micrometer is the proper tool to use but in a pinch a good caliper or micrometer will work.

bearing inserts are standard or over sized they are thicker to cover the wear there is no such thing as undersized

This has been a topic discussed with this individual several times. ....UNERSIZED....IS THE INDUSTRY ACCEPTED TERMINOLOGY FOR AN ENGINE BEARING THAT HAS A THICKER SHELL TO FIT A CRANKSHAFT THAT HAS BEEN GROUND OR RESIZED TO A SMALLER DIAMETER. Please don’t confuse things more, the original poster has graciously came here for some HELP.

(quoted from post at 05:21:06 06/02/20) bearing inserts are standard or over sized they are thicker to cover the wear there is no such thing as undersized

Click to expand...

Correct sir, some people say undersized, but it is the crank that is undersized. Not in this case though. I will mike the insert thickness compared to old one to see if that is it.
The caps are in correct order and caps are numbered, number to the camshaft side. Dang it sure seems right.
Thank you all for your responses.
Cowboy Badger

(quoted from post at 05:45:58 06/02/20)

(quoted from post at 05:21:06 06/02/20) bearing inserts are standard or over sized they are thicker to cover the wear there is no such thing as undersized

Click to expand...

Correct sir, some people say undersized, but it is the crank that is undersized. Not in this case though. I will mike the insert thickness compared to old one to see if that is it.
The caps are in correct order and caps are numbered, number to the camshaft side. Dang it sure seems right.
Thank you all for your responses.
Cowboy Badger

Click to expand...

These other guys have a ton of more experience than I do, but...
when I put new bearings in my 460 and much earlier a 560 the bearing inserts were stamped .010, .020, .030 if the bearings were oversized. I also studied as hard as I could because one of these motors had two different style bearings with a flange on them. You had to get the right one or it wouldn't fit. Just something that is easy to look for and if someone somewhere was not careful you could of, as stated, end up with the wrong bearings. If they are stamped it would be an easy thing to look for. And new bearing will be tighter for a little while even if they are the right size. I can't remember how tight they were on my applications but it did tighten up as far as turning the crank by hand vs using the starter or a wrench or what ever. Good luck. Regards, John.

get your plastigauge out and check the brgs. you will find out fast whats going on. you want .0015 clearance. why guess and wonder.

(quoted from post at 09:13:44 06/02/20) get your plastigauge out and check the brgs. you will find out fast whats going on. you want .0015 clearance. why guess and wonder.

Click to expand...

I got the red today. Yesterday they only had the blue .004 to
.006 . So on to that and see what 115 ft lbs does to it.

also,... once torqued you should be able to slide the rod side ways back and forth for side end play. if you cant do that you have a problem. and no,... the brg. is not tighter because of new and get loose. if that was the case the brgs. would be screwed right away by turning the crank. platigauge is your best friend doing this.

I agree, as a mechanic since 1968 and associated with crankshaft work before that, It is undersized bearing inserts on smaller journals. There is no other term used by the broad stroke of mechanics dealerships, instructors, parts counters, and technicians I have encountered or researched, or purchased from in all those years.
I also think either a mixed up cap, or turned "end for end". (possibly an Indiana term there) Jim

you need the green stuff.

You need to check a few things here. First are the tabs on the inserts on the same side yet such they come against the bock and cap so it doesn't spin in the journal. Then with the bearings out look at the inserts to make sure you got the correct bearings . Yes they can get switched in the box though rather rare to happen. Check all bearing inserts as one journal may have been turned in the past to a different size. If you have one bearing a few thousandths off and in the wrong location it will be tight. The tab I speak of is the small section that is punched out at the end of the insert. Are the inserts in so that the tab is in the cutout on the block and cap. If not could just wedge it tight. if all is good then you must check the insert thickness. And now if all is still good recheck your numbers on the caps. They should number in order from the radiator end of the block starting with 1 . The cut out for the bearing tabs should also be on the same side yet across the bolt from each other. With a piece of clean enough to eat off from rag or better yet leather tighten the crank in place to do your plastigage clearance check. If it now turns with a tight spot then goes past it is your crank journals out of roundness causing the problem. So now you have to decide whether to pull and have ground or not. Do one journal at a time and remove each on as you do this to know if it is an out of round condition. Mic the rods while you are at it . Might find they need turned also.

I'm blind i guess. Main caps numbers go
to camshaft side. Tangs are NOT together.
I ended with the tangs on same side and
couldn't see numbers were wrong. Flipped
em around, torques up fine. Plastigauge
show a bit over .0015" clearance.
Thanks everyone