[93yjsahara]

rebuilding a 4.0 and the lower main bearings....you can rotate them along the crank just a bit, like 1/8"


is this right?

 

[jopes]

are you saying the mains are moving under the main caps after they have been torqued down?

 

[ForestCam]

Where's your plastigage????

 

[93yjsahara]

i have even put the caps on yet, but you can slide the bearings around, side to side and front to back..... just dont seem quite right to me, but then agian what do i know

 

[Keith]

huh?

 

[CumminsBronco]

i haven't even put the caps on yet, but you can slide the

........fixed it for you, I think.
No main bearing I've ever installed will move around within the cap or saddle. Sounds to me like you have the wrong bearings. Each half should be a snug fit into it's cap or saddle, almost a "snap-in" fit.

 

[TINY]

the bearings should have a flat edge that sticks out at each end. and the cap and block should have flat grooves also at the ends to keep from what you say is happening. they don't snap going in but they do stay in place once you have centered them.

 

[bigfodee]

same project..


yeah, i have not put the caps on and torqued them down yet. the bearings are std, but its as if they are a little too small. the ends #1 and #7 are a perfect fit, but 2-6 can slide around, there is a little lip that keeps it from turning too far.


sorry, im not great at explaing it, but picture your hand shaped like a C as if you're holding a glass or something. you can slide your wrist around the glass a lil bit

 

[Pdaddy]

Did you have the crank machined or did you even check to see if it is within tolerances?

 

[Pin Head]

Maybe the block was line bored at some point. Were the old bearings marked as being oversize in the outside dimension? This would be something like 0.010 - 0.010 or .010 - std. Just measure the clearance with plastigauge and you will find out if it is right or not.

 

[bigfodee]

i checked the crank with micrometers

thats the thing, if anything was bored the STD bearings would be too big, not too small

 

[JeepCrawler98]

i checked the crank with micrometers

thats the thing, if anything was bored the STD bearings would be too big, not too small

If you take away metal - aka boring; wouldnt it result in a looser fit, which would mean theyre too small?

 

[Keith]

I would not worry about it.
Has a bearing ever been spun in this motor? Bearings us "Crush" to seat themselves in the saddles, that is what keeps them from spinning, not the alignment notches. You will probably notice that the ends of the bearings stick up from the egde of the saddles a bit before they have been torqued

 

[Bgcj5]

That sounds kinda sketchy to me, I have put together a few motors and they have never had any play in the bearings. once u set them in place they really shouldnt be moving. I would be gettin some plastigage and double checking that, course u should be using that anyway.

 

[HaWiiLuVeR]

a lot of main bearings have the surface on each side of the bearings so they cant use much of a crushing force. sounds like you are saying they arent a full 180* but maybe 170* allowing you to rotate them the extra 10* end to end. i would take them back and get a new set to see if you just got a bung set. then just continue using those micrometers, cus plastigauge....... ihhhh