Rod bearing wear

[ThaDude]

I'm tearing down a 1991 KA24DE with 800 miles on the rebuild. She developed a small knock, so I ripped her out before any damage to the crank.
Here is one of the rod bearings:



So my question, is the a result of improper installation? Oil starvation? The oil did get contaminated by fuel from a stuck open fuel injector at one point, but the car was only started/idle for diagnostics, and oil was changed before driven.

[rcdad123]

looks like there was not enough bearing clearance. re check the clearance.

[dawagarage]

was the crank checked for straightness using a mic?

[karkas9]

every clearance has its specific oil thickness to compensate. most engine builders find an oil that matches the clearance they always try to achieve just for consistency and the fact that they have tested it. also they see what oil pressure that setup gets at various points in the oil lines in the block. of course they only do that once for the clearance/oil combo and just stick with assuming all engines(same engine model) are equal. all that said the range they go is still around 0.01" from oe spec...
what someone who is not an engine builder but want to build an engine would usually do is to get the block to a machinist and give him the oe clearances from the FSM and ask the machinist to measure what is his engine clearances are (for piston to cyl wall, all the rods, bearings, all that you want to replace that is worn and needs a specific clearance)..then you can see if you within spec. obviously he can tell you whats up and where to go from there. but generally if out of std spec, you have to machine either the part(i.e crank) or block(cyl wall) to get to the next size up because they(aftermarket and/or oe suppliers) don't make parts in infinite sizes..then get those parts and you can assemble your engine with the parts.. but not so quickly.. you have to use the clearance gauge/stick/colored-strip-of-plastic to find clearance to very good accuracy (0.00x usually), then average the values for a clearance of a specific part to find where you standing, of course considering all the extremes.this is where the oil viscosity game comes in to play; if you r toward the limit of + clearance then you can use slightly thicker oil but first asking your machinist and/or research for your situation. the other variables to consider are the application of the engine, power, rotational speeds, heat, weather, etc. there is also situation where you are toward -ive clearance then you can use sand paper then proper wash or more machining if applicable or ask machinist..
if you dont wanna do ^^ then stop thinking you can build and engine and expect it to last long.

[KoukiMonsta]

^^ hard to read, but some good info.

[karkas9]

bumpo..
in your case it looks like you have either off clearance (wither too much or too little)
or contamination from sandpaper or scotch brite or something like aluminum/silica oxide
or you running too hot
or worn out oil pump
or bad oil filter
or alot more reasons i cant think of..
i hope others learn from your mishap cz there are many threads just like this on every car forum

[ThaDude]

Ok thanks for the greeat information guys!

I will try to clear some things up here. The block had been decked/honed/bored os, the crank was ground and polished, balanced with the rods/pistons. The Machinist sold me these bearings when I picked up the crank and block. I did use platic guage to check clearance on main bearings, but not on the rods (Idk why now). I have manley h beam rods with ARP bolts, but no arp main studs.
The oil pump was also rebuilt. Oil was changed 5 times during the 800 miles with 5w-30 castrol gtx (was cheap) and Bosch oil filters.
It DID run hot a couple times do to air in the system, but it never over heated.

[ThaDude]

Been really busy lately, but I had a chance to measure this rod bearing and it is indeed the wrong size! Lesson learned. The machinist told me to order undersize 0.25, but changed his mind and said he would get them. This guy is a master, so I trusted him. Too much I guess!
Factory specs from FSM state undersize 0.25mm thickness should be 0.0769 - 0.0772 in. Mine is 0.0699 in.!
I remember why I didn't plastic gauge the rods, I kept messing up the line taking off the rod cap! Any good advice on doing this?
Thanks again everyone!

[UNITEDMASTER]

Get an inside mic,also never trust new rods,always get them checked &resize the big end if needed

[ThaDude]

Ok that eliminates plastic crap guage all together, sounds great. Thanks. I assumed.the machinist had bluelrinted it. With all the work he was doing to it, i figured it was necessary for him to mic it all out to do the work.
I need get my hands on some decent micrometers/measuring tools!

[karkas9]

u still have to check with plastic gauge because when you torque the fasteners on the caps there is deformation on the bearing and also make sure you torque when checking with mic.