Movement on Connecting Rods on Crankshaft

robbyb20

Well-known member
Oct 2, 2019
145
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Seattle
Last weekend i resealed the sump with silicone (it was dripping out the front of sump if pointed downwards on hill) and while i had it off, i checked some of the con rods for any movement.

I did not see any in the front 4 but the back 4(5,6,7,8) had a bit of clearance and they moved forward/backwards a 1-2cm. I did not have the tools at the time to get those caps off to check them so I figured i would just redo all the bearings (mains and con rods) this weekend.

While reading up on the overhaul manual, i came across this passage on page 40 of the 4.0 & 4.6 Litre V8 Engine Overhaul Manual

"Check connecting rods move freely sideways on crankshaft. Tightness indicates insufficient bearing clearance or misaligned connecting rod."

Im inclined to think that this means the crankshaft should rotate freely side to side but want to make sure im not misunderstanding and looking for the same movement I already felt last weekend.

I want to do this anyways since ive already replaced the oil pump and on a cold start it still takes awhile (5-9 seconds) to build oil pressure and it doesnt hurt to know the condition of the bearings since I dont have any service history for this vehicle.

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p m

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I popped the oil pan on my Classic's 4.0/3.9 hybrid, and found the same - front 4 con rods had almost no play, and some of the back 4 did. My guess is about a couple of tenths of a millimeter. All journals were over 55.5mm, no measurable ellipticity.
I replaced the rod bearing shells and called it done. I've done the same on my D1 at a 250-kmi mark, with the same results; now, at 288k, it is still okay.
 

robbyb20

Well-known member
Oct 2, 2019
145
16
Seattle
Good to know! Ill measure then too with platigauge and see if they are out of spec. Hoping for an easy job.
 

p m

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Apr 19, 2004
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Good to know! Ill measure then too with platigauge and see if they are out of spec. Hoping for an easy job.
I am not sure about the value of plastigauge.
In my case, the engine was of unclear vintage, but definitely with close to 100k miles. All top rod bearing shells showed copper, so they should be replaced regardless; past that, the direct measurements of journal diameters gives a good idea - whether the crank can be kept as is, or reground or whatever.
 
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robbyb20

Well-known member
Oct 2, 2019
145
16
Seattle
I am not sure about the value of plastigauge.
In my case, the engine was of unclear vintage, but definitely with close to 100k miles. All top rod bearing shells showed copper, so they should be replaced regardless; past that, the direct measurements of journal diameters gives a good idea - whether the crank can be kept as is, or reground or whatever.

Thats true, I wonder if oriellys or napa rent out calipers. Im curious what the wear on the bearings are as well.
 

robbyb20

Well-known member
Oct 2, 2019
145
16
Seattle
Only got the connecting rods done last Saturday. bearings were showing copper from wear. also took the front plate off to inspect the new oil pump I put in and it looks good, no scoring.

If I have time in the next couple weeks ill do the mains and see what comes of it. I feel like I may be tinkering too much with a truck that hasnt let me down engine performance wise just to quiet it down a little bit on start up and build up oil pressure faster.
 
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