Jimmyrigged
On the wastegate
Crank was good
What would cause this weird bearing wear?
- Thread starter DartVadar
- Start date
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That's good, so it was either incorrect assembly lube, dirt or too tight? So the parts are good as long as the clearance is good?
marksmopar1
Well-Known Member
All of the above, but also check the crank straightness...be sure it is not bent?
If bent, I have seen wear being uneven across all the bearings and it can be seen even on just one bearing. The wear on your bearings could be a bent crank. Worth a check if its out.
If bent, I have seen wear being uneven across all the bearings and it can be seen even on just one bearing. The wear on your bearings could be a bent crank. Worth a check if its out.
The two outside bearings dont look like that, its only the middle three that do. But If I had a bent crank wouldn't the car have vibration issues? Because it was nice and smooth. How would I check that anyways?
Don't mean to hijack, hope it's relative to the thread. What about using STP as assembly lube?
Jimmyrigged
On the wastegate
Bearing's have heat mark's (lack of oil-oil also cool's). crank install was not to tight so it has oil clearance. so I would say there is a lubrication problem to the crank.
marksmopar1
Well-Known Member
Vibration, not always. it could be a slight bend but it can show up in just what you have. The other thing giving much the same is the align hone, if off in anyway same results. Although you did say the crank turned freely when bolted in. It's just another thing I would check, a good crank shop should be able to confirm then at least you can feel safe about the crank.
STP is a good assy lube, I've used it many times. :cheers:
Casite motor honey also works well, in fact a little better....
marksmopar1
Well-Known Member
If bent, yes heat will become a factor as well. Clearances would then be tight in one area loose in another, Lubrication then is useless and destroys bearings, over heats them and same results as seen. The tolerances just increase and the bearings are pounded out.
Jimmyrigged
On the wastegate
I agree with marksmopar1. crank's need to be perfect for the longevity of the motor. when I was taught how to build motors over 35 year's ago those old school motor heads were using non detergent motor oil (30w) for engine assembly lube and they never had any bearing failure. they said assembly oil is just for that. the need to pre-lube (prime the system) before the first start up was critical. I remember priming on them engines for half an hour and turning the crank over every two to five minutes (under there close supervision and smart remark's of my stupid youth) before we fired them and then we would run them at 2k rpm for another half hour. with all the new assembly lube on the market I doubt that is a problem.
Wouldn't a bent cranshaft have been seen when they turned it at the shop? I really hope that it isn't bent. If it was bent wouldn't the wear be the same on both sides of the bearing and not just the top and bottom of one side like mine?
If it makes a difference I remember looking at the balancer when I was timing it and it didn't wobble or anything, was perfectly even
If it makes a difference I remember looking at the balancer when I was timing it and it didn't wobble or anything, was perfectly even
moper
Well-Known Member
Sorry if I missed your answer - was the crank turned undersize and then polished by a shop?
marksmopar1
Well-Known Member
DartVader
Yes, it could be fine....Just a suggestion worth a check, bent can be unnoticed and very slight, truth, it is not likely.....but?
Yes, it could be fine....Just a suggestion worth a check, bent can be unnoticed and very slight, truth, it is not likely.....but?
Jimmyrigged
On the wastegate
Well, yes if they are paying attention. to test it first take all cap's and bearing's out on all of them except the ends leave these on and torqued down. set up a dial indicator with a solid base on each crank journal(center journal's). turn the crank and observe the readings on each one. after that remove the cap's and bearing's off of the ends and install the bearing's and cap's on the crank's center journal's and torque them to spec and check the crank end's out of round. with that many cap's missing during the test I would go to .008" out on each one. this is only a get close test. if it is out the crank need's to go back to the crank shop.
moper
Well-Known Member
I'm still at a loss for what was actually done when you put it together with those bearings. Or am I confused, and you didn;t put it together?
Anyway - it looks to me like too much oil clearance, probably a lot of tpaer on the journals, and oil wedge break down as a result. That lets the crank shift around in the block, and in some cases pushes it in one direction or another, creating the wear you see. I'd expect to see more copper is the crank was bent, and a lot more heat in the bearings.
In my opinion you should be using the right tools to measure the crank for taper, and crank and and the bearing bores to calculate clearance. Plastigage will not show taper. If you have oil clearance greater than .0025 I'd look at running a bearing to take up some of that. I generaly like to have between .002-.0025 on the mains.
Anyway - it looks to me like too much oil clearance, probably a lot of tpaer on the journals, and oil wedge break down as a result. That lets the crank shift around in the block, and in some cases pushes it in one direction or another, creating the wear you see. I'd expect to see more copper is the crank was bent, and a lot more heat in the bearings.
In my opinion you should be using the right tools to measure the crank for taper, and crank and and the bearing bores to calculate clearance. Plastigage will not show taper. If you have oil clearance greater than .0025 I'd look at running a bearing to take up some of that. I generaly like to have between .002-.0025 on the mains.
TrailBeast
AKA Mopars4us on Youtube
I can't remember the name of the lube I use but it's a dark red color and I have never had a issue with it.
Now you got me worried about my eddy heads though
Snake Oil
Seriously, not a joke and I have some here.
Dark candy red and real thick and sticky.
I put the motor together, the crank I think was just polished a little bit, not much was done to it. Otherwise it was completely stock. Now the crank was turned under and polished and never installed, and it was checked so I should be nice and true.
Too much clearance? that could be it. So a bent crank would cause more damage? Now when I put it back together I should measure for the taper? so that may have been the issue before. That is done with a dial indicator right? I like jimmyrigged's suggestion, I may try that out.
Since the crank was pretty much untouched from stock is it normal for the journals to have some taper to them? or are they typically nice and straight from the factory
Jimmyrigged
On the wastegate
I have seen real good and bad new from the factory and that is on all the big three manufactures during the seventy's and eighty's because of there interest in increased production and less quality control. A part that has been rebuilt should have been checked for these type of problem's and a quality machine shop should keep there tool's sharp and true also. Quality control is what we as consumers struggle to deal with and makes our project's harder to do-this makes my head hurt:banghead:
doogievlg
Well-Known Member
Crap makes a absolute mess!
To me it sounds like the op has 2 options. Go buy a stroker kit and have fun or just go get a new crank. Personally I would go with option number one. Just kidding!
I wouldn't get too worked up about it man. These threads can cause people to panic. I would take the crank back to the machine shop and get it checked out. If everything looks good then get some engine assembly lube and throw it back together. I have heard of people getting a bad set of bearings and it going south quick.
Take your time and triple check all clearances also. Good luck
n.y.340 dart
Well-Known Member
Mic the crank mic the bearings assembled with caps. deduct for clearance clean every thing spotless good assembly lube should be fine. Has to be clean!
moper
Well-Known Member
Taper is measured. You get the crank to 70° temperature and get a micrometer. You measure each journal at a minimum of two points accross the width of each journal. (note rod throws have 2 journals per throw) Taper will show up if you measure properly and consistently. Or - bring the crank to the shop that turned it (may not be where you paid for it) and have them chuck it up and run an Arnold gage on it. That will definately find any surface issues.
If the original crank was only polished when the engine was rebuilt there's a very good chance the journals had a bundh of taper. Usually the wear leaves it "in spec" but having some, then it's polished which makes what's there worse.
If the original crank was only polished when the engine was rebuilt there's a very good chance the journals had a bundh of taper. Usually the wear leaves it "in spec" but having some, then it's polished which makes what's there worse.
Thats what I was told to do when I checked the bearing clearances, but I need micrometers, I may be able to find a pair of those, or borrow them. Yes I am going to make sure its as clean as possible!
I will take it to the shop, and bring in the bearings for them to look at and get everything checked out. I remember this time when I took the crank in to be turned they called me and said that the crank was ok, but not good compared to what the spec was, so I think it was a bit outa wack (just remembered that now) and they recommended to turn it.
Im still new to this, but this first time was kinda a learning experience, it costed me some cash, but I feel that I learned how to do it right now! and check EVERYTHING multiple times. I have a huge list of everything to measure and record now.
To clarify, from what I am understanding my issue seems to be a mixture of too tight clearances and some taper to the journals? This caused the uneven and accelerated wear on my bearings.
What were the crank bearing clearances upon the first assembly?
moper
Well-Known Member
Bearings are protected from physical damage only by oil pressure. Pressure is cause by resistance to flow - in bearings' case that comes from proper clearances and properly shaped (parallel) surfaces on the bearings and crank's journals. Especially on the mains, where the oil is pumped in, and then has to go through the crank to the rod bearings, journal finish and clearance is critical. I like a main clearance a little tighter, beacuse there's less leakage before the rod bearings get it. If the jourrnal(s) are tapered, the oil can escape and will not have a consistent load carrying capacity. This can be very localized on the bearing. Too loose is worse IMO in a main clearance than too tight. That's what I see on yours. The journal surface isn't truly flat, and the oil clearance may be a little too wide at some points around it. Remember the bearing bore is not perfectly round - it's tghtest at the top and botton perpendicular to the cap parting line. If the crank is not flat and the journal a little small because it was only polished you're asking for problems in the long term. Contaminants will scrape along the bearing making scoring down into the copper, or embed in the surface where you can see them. The marks are a bit different than yours. Oil starvation even at startup would affect all of them, and #s 1 and 5 are fine. So it's something else in my opinion. If you didn't measure (you used plastigage) you simply don't know if the journal was good. You know the clearance was in spec. If as you say the shop said it was marginal but usable - I'd say that's some confirmation. The Arnold gage they use is much more precise than a micrometer. A mic will see the taper if the temperature is right, enough measurements are taken, and the person measuring can read it correctly.
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