I pulled the pan to inspect a spare 280Z engine and noticed the rod journals have some discoloring from heat. Other journals showed some discoloration but #3 was the most noticeable. The rod and cap didn't show any signs of discoloration and the bearing halves looked ok. Could this be from factory heat treating? I was told the engine has about 65K miles on it. Only other times I've seen this was from a spun bearing or a crank that has been welded and reground.
I won't be much help, but here's my best shot.
A buddy rebuilt his XR650L. We were both horrified to see the crank discolored by heat, much worse than your pics. Not knowing what else to do, I suggested he slap it together, and see. Many thousands of miles later, it is still going strong.
I'd try to slip a feeler gauge between the rod cap and crank. Of course, I have no clue what that measurement should be, but it should have SOME clearance. Good luck.
Plastigage......If it is OK, put it back together and forget about it....
Rog
I've taken apart engines that looked like that and were not worn out and were running fine, the car around them just fell apart. My guess is that cheap oil was used and not changed that often and the engine may have run hotter then ideal cooking the oil. That bearing looks fine but if you're worried swap out the bearings with new. You just need to measure the crank to confirm size. I have replaced the rod bearings on two different engines doing this and both ran for many miles afterward.
Bearing looks great, crank surface looks smooth, I would run it.
Discoloring is outside of the surface working the bearing, no biggie; more concerned about the cracks parallel to the centerline.
Plastigauge rocks!
I ordered some Plastigauge from my local parts store last night and just picked it up on my lunch break. Sad thing is the kid behind the parts counter kept thinking I wanted green plastidip 
. I'll see how things check out tonight.
The surface can be cleaned with a bit of emery cloth wrapped around it, then wrap a shoelace around the emery; tug on each end of the string to run the cloth around with even pressure all over.
In my unprofessional opinion it looks to be a forged steel crank. Based on the journal not being all chewed up I would guess the discoloration is from the journals being induction hardened (or maybe flame) at the factory, which is typical of a steel crank.
PseudoSport wrote: I ordered some Plastigauge from my local parts store last night and just picked it up on my lunch break. Sad thing is the kid behind the parts counter kept thinking I wanted green plasidip
Couple years back I asked the manager (kid behind the counter) for plastagauge and the kid kept insisting it was in the isle with the autometer stuff. I had to get the old guy that delivered parts part time to help me.
dean1484 wrote:PseudoSport wrote: I ordered some Plastigauge from my local parts store last night and just picked it up on my lunch break. Sad thing is the kid behind the parts counter kept thinking I wanted green plasidipCouple years back I asked the manager (kid behind the counter) for plastagauge and the kid kept insisting it was in the isle with the autometer stuff. I had to get the old guy that delivered parts part time to help me.
I recently got in a argument with the kid behind the counter over freaking specialty belts. Gave him a part # and he asked what i was for and i told him and we went round and round until i left and ordered it online.....
HonestSpeedShop wrote:dean1484 wrote:I recently got in a argument with the kid behind the counter over freaking specialty belts. Gave him a part # and he asked what i was for and i told him and we went round and round until i left and ordered it online.....PseudoSport wrote: I ordered some Plastigauge from my local parts store last night and just picked it up on my lunch break. Sad thing is the kid behind the parts counter kept thinking I wanted green plasidipCouple years back I asked the manager (kid behind the counter) for plastagauge and the kid kept insisting it was in the isle with the autometer stuff. I had to get the old guy that delivered parts part time to help me.
Lets not go down that road...we ALL have that story, in one form or another. This thread will spiral out of control quick. Lets just say, its easier to gain parts knowledge than it is to get paid well for having parts knowledge. If the opposite were true, there would be more people with parts knowledge employed in places where they sell parts. The chains dont want you to be able to think critically or make logical decisions to solve problems. They want an $8.50/hr parts monkey with flexible schdule availability. Knowledge is a nice-to-have, not mandatory. The big chains have invested literally dozens of dollars to build 80's-era DOS based parts search software that (in their corporate minds) should definitely never end up getting you the wrong alternator for your capri project...
4cylndrfury wrote: ...The chains dont want you to be able to think critically or make logical decisions to solve problems. They want an $8.50/hr parts monkey with flexible schdule availability...
While at the same time their HR/Marketing Dept insisting that their employees are "empowered" to help and make suggestions.
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