satburn

So I'm all excited with the arrival of my bearings only to be disappointed when I start to take the wrist pin out of the old #1 piston. It won't move. Uh oh... I take it over to the press, it comes out quasi easily but after I remove it, I find this...





Son of a... ARGH! What the? Alright, so now lets change the diagnosis from stuck injector to an attempted seize of the wrist pin, which would explain the piston wanting to smack the cylinder wall. But why? The lubraction of the top of the rod doesn't make sense to me, there's a hole in the top of the rod, but other than than that there's a cooling jet squirting oil into the cylinder. How does this thing get lubricated? A slinging effect?

Also, after I checked the other bearings, they are all brassy and all have this interesting "blemish" on them. Is this normal?

ratsun

OK I never had one of these engines apart so I may be way off but....
In the Chev big blocks I used to work on the pin was oiled mainly by the oil squishing out of the side play between the rods and the crank. Excessive idling was a common reason for wrist pin (as well as cam/lifter ) failure as little oil gets slung up there during a low idle. It kind of looks like the bearing is pitted like something etched it? Did this engine sit unused for any extended period?

satburn

Good question, one that I don't have the answer to for the first 85,000 miles of this truck's life. I don't believe it sat for any period of time, but I can't account for the first owner.

Yes, it's etched and although the pic doesn't show it well, there is a rainbow of colors in there. It sure looks like it went dry at one time for whatever reason.

ratsun

The rainbow of colors is probably just from the heat.
I know you stated before in your other post that the cooling jet nozzle looked good but if the other bearings look good I would really suspect a problem with it however if the other bearings show signs of scuffing I would suspect the previous owner did serious amounts of low RPM idling with low oil levels? Its tough to tell but the last picture seems to show scuff marks as well.

kawi600

that blemish is where the metal journal is wrapped around and joined. Looks kind of like a puzzle piece.
Looks like maybe there was a gap problem or something got in the oil. That rod and wrist pin is obviously toast
How do the crank journals look?

satburn

Good actually, the bottom of the engine is fine, its the top that went to the dump. The bottom bearings are still grey even, rod journals look great, mains good too. I'm going to look hard tonight at those cooling jets.

Lil Dog

Having the top of the bearing rod end wear is not a typical failure point. The only time you have force on that part of the rod is at very low manifold pressure and on the cross over from exhaust to intake stroke. There is an inertial reversal on the pin, however the load is small compared to the load at peak firing pressure. Maybe high engine RPM might make it more of a factor, like over 3500???

Being that #1 is closest to the oil pump, I would have suspected oil starvation to be prevalent on the rear engine bearing areas. That is not a typical failure.

satburn

The plug to access the gov. springs still had the anti-tamper wire in place, so unless the previous owner replaced the pump, I doubt it saw high rpms. This "knock" has always been there since I've owned it, I believe the damage was already there prior to me running a GSK (I was just ignorant of the noise). I agree this isn't typical and that's what has me puzzled. How could something have failed so catastrophically at one point, but then continue on as if the problem was fixed but the damage not? The piston still swiviled on the wrist pin just fine, despite the damage and the skirt looked as though it seized to the bore once and then was broke free, then the rings "re-honed" the bore back clean. The skirt doesn't appear to have contacted the wall since the incident. It's as though oiling for the upper end of that one bore stopped one day for some reason, they got it to break free again, filled it back up with oil, fixed it, whatever and continued on...

Lil Dog

My business partner was just lookin over my shoulder and we noticed that the oil hole was on the top of the rod. Is that typical or is this the only bearing that was in that way? To me I would expect the oil hole to be on the on the side close to the big end of the rod...

This may be a factory issue...

satburn

It is in the top and yeah I was the same way. The hole in the bearing matches the hole in the top of the rod. They do match and they are all oriented the same. That's why I was saying that it doesn't make sense to me how this thing is oiled. It would seem to me that it would be a stroke of luck that any oil whatsoever would find its way down that hole and into the bearing.

Lil Dog

That is weird.. Wow those oil jets are more important than you think. I have never had one of these babies apart so its all new to me..

satburn

Alright, I got all of the wrist pin bearings out and new ones coming. Does anybody have any tips for re-installing? The top of the rod has a matching angle with the bearing, in other words it isn't a square face that I'll be pressing against. Do they have a special press plate available for this, like a pilot pin with an angle matching shoulder?

satburn

class, anyone, anyone?

Mcmopar

Correct me if I am wrong, but arn't these supposed to be a hone to fit pin with the locks in hte piston to hold the pins in?

HOHN

A lot of engines use "forced pin oiling" for just this reason. In this case, the oil that's scraped off the bore walls is "forced" into the pin area to lube it.

The oiling hole on top is crucial, because the oil squirters are spraying oil at the underside of the piston, and this oiling hole gets its supply of oil from there.

There won't really be any splash lubing from the crank-- it's all from the oil squirters in the galleys. That spray gets everywhere is a a huge reason why these engines last so long-- the pistons are oil cooled and the whole rotating/reciprocating assembly is pretty well lubed.

FYI-- this is also why Honda engines last so long despite short connecting rods that load the bores.

Since the damage appearts to be on more than one cyclinder, I'd say you can't really point to just one oil squirter. Sounds like a different, bigger problem.

JMO