Bearing wear diagnosis help! (pics)

[CyFi6]

Hey everyone i recently picked up a running 7mgte shortblock from a local. It was supposedly build approximately 10k miles ago by a reputable machine shop. I pulled it apart, and it has OEM Toyota select fit bearings in it, so i was happy about that, but for some reason, one bearing on one rod is showing some tapered wear. Its easy to see that one side of the bearing is seeing more wear than the other, which could be from a bent rod or tapered crank, if i am correct to say that. All other bearing top halves were slightly worn, but not through the second layer like this one is, and all the rest were evenly worn.

What confuses me though is why only the top half is exibiting this wear. I understand the top half sees all the load, but if a bent rod was the case or a tapered crank was the case, wouldnt i see similar (maybe less severe) wear on the bottom half? The bottom half seems to show zero wear associated with one side over the other. Experienced engine builders please help me out! Should i get the crank and rod measured to try to figure out the problem? If the rod or crank is the problem, will i have to have the entire set of rods and journals machined or can i repair just this one rod? Thanks.

By the way, after the bearing was removed i inspected the backside and the cap, and neither showed any indication of material stuck behind the bearing.

 

[IJ.]

I would suspect egg shaped big end holes from those pics/descriptions, also looks like a very dirty build.

 

[CyFi6]

Thanks for the ideas IJ. Doing a rough measurement with a caliper, i saw less than .0005" difference between vertical and horizontal measurement, though i understand a caliper isnt going to show me much. I will have it professionally measured. How much out of round do you suppose it takes to see this kind of wear? Also, when you say "dirty build" what do you mean and why do you say that? Is that because of the light scratches you can see in the bearing? Is it possible those are from lack of maintenance or hard driving rather than a poor build?

 

[Doward]

Just from simply not cleaning the block enough.

When I assembled my 7M, I would (dead serious here) have NO qualms about eating off of it.

Though I will say, I would have been pissed, as I'd have to clean the block AGAIN.

 

[Poodles]

Flash with show EVERY imperfection in that bearing surface...

That and the oil burn on the rods...

 

[CyFi6]

If you guys are talking about the dirt/debris sitting on it right now, thats because ive been messing around with the rod and bearing and i havent cared to keep it clean at all right now. Its out of the engine and dry and in my room, so there's dust and rag particles on it, not like im assembling it like this. Any other ideas? How would a lightly egg shaped big end cause more wear on one side on the top, but not on the bottom?

 

[CyFi6]

Quick question, in the bearing chart in the tsrm (http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=70) why are there blank spots?

 

[Jeff Lange]

Because there are 3 sizes of rod, 3 sizes of crank pin, and 5 bearing sizes.

Jeff

 

[TheNewRed]

Because there are 3 sizes of rod, 3 sizes of crank pin, and 5 bearing sizes.

Jeff

o no, not this again LOL.

 

[CyFi6]

Thanks, that makes sense now just needed a wake up. My next step is to get a hold of some measuring tools and figure out what my problem is as well as what i need to repair it. Once i get everything measured its cake. Hard part is finding someone to let me use their tools, might end up having to have a machine shop measure everything for me.

 

[kotu100]

check if you have a wholesale tool near you, i picked up all the tools i needed to spec my engine rebuild for less than $100.

 

[CyFi6]

Ah, thanks for the tip, looks like they are only in the east area of the US. Does anyone have any other suggestions for affordable brands of Mics and other precision tools? (Mitutuyo is over $100 for one mic, i dont have that kind of money to dispose of at this point in my life)

 

[kotu100]

well you could always get it shipped from their site, but if you're lookin for the name brand stuff you're gonna be spending the cash either way.

some of the stuff i got from there,
http://www.wttool.com/product-exec/product_id/17516/nm/Thickness_Gage_WT_Import_
http://www.wttool.com/category-exec/category_id/17312/nm/0_to_3_Inch_Micrometer_Set
http://www.wttool.com/product-exec/product_id/17322/nm/Dial_Indicator_Magnetic_Base_Set_WT_Import_
http://www.wttool.com/product-exec/...tional_Superscreen_Electronic_Digital_Caliper
http://www.wttool.com/product-exec/product_id/17491/nm/6_Pc_Telescoping_Gage_Set

 

[CyFi6]

Those mics and snap gauges are tempting, they are all i would need. All i am worried about is accuracy with the mics. Durability isnt a huge deal to me as they aren't going to be used hard or often. Can you confirm that they really are accurate?

 

[kotu100]

Those mics and snap gauges are tempting, they are all i would need. All i am worried about is accuracy with the mics. Durability isnt a huge deal to me as they aren't going to be used hard or often. Can you confirm that they really are accurate?

i checked them against the digi calipers, and a set of Mitutuyo mics and they are accurate. they're acutally pretty easy to get an accurate reading out of, and not finicky like some other mics i've used. im not expert by any means but i have a few years machining exp.

 

[REG8000]

If you guys are talking about the dirt/debris sitting on it right now, thats because ive been messing around with the rod and bearing and i havent cared to keep it clean at all right now. Its out of the engine and dry and in my room, so there's dust and rag particles on it, not like im assembling it like this. Any other ideas? How would a lightly egg shaped big end cause more wear on one side on the top, but not on the bottom?

hi
if you are unsure about it do it right. take it to a good!! shop and have it turned . they pull the plugs on the rod jurnals and clean the crank. i have seen them pluged along with the filter scren on the oil pump when not useing a gasket. they will be glad to check the rod, if its bent i would check the piston pin also. once it is turned you should no longer have a ploblem good luck

 

[CyFi6]

What is the safest max oil clearance to run on the main bearings without having to worry about excessive wear or oil pressure drop? I clearanced my mains to find the crank is a bit smaller than spec, and it puts my oil clearance to about .002" with a #5 bearing. Is this too large? Should i have the crank ground undersized and use an undersized bearing? If i do this must the main webs be line bored? (The TSRM never states anywhere it needs to be done when using an undersized bearing, but it would only make sense considering they are difference size main bores. Or does the machinist match the crank journals to the main bores and bearing so the proper clearance is achieved on each main, making line boring unnecessary?) It is odd, because i have three cranks, and each one of them measure the same main journal diameter, which is slightly smaller than the TSRM spec, boggles my mind how all three would be exactly the same.

EDIT, this crank also came out of a running motor with the same oil clearance, and the bearings looked perfect, very minimal wear, but i have no idea what the oil pressure was like.

Also, i recently learned that this motor had a BHG at some point, could this be the reason the upper bearing halves are so worn on the rods?