engine and drivetrain Short trip, spun rod bearing

[reuben2002]

I was travelling to Medford on Thursday to get some replacement sheetmetal, and I got about 150 miles when a rod knock developed. Took all day for a freind to come and get me and tow it back to Walla Walla (but now I can recite the history of Shaniko from memory). Pulled the engine on Friday and tore the bottom end down, got a spun rod bearing on cylinder 2.

What pisses me off the most is that I only have about 1500 miles on a fresh rebuild. I did the work, and since it is only the second engine I have rebuilt, I was extra careful and meticulous. The crank journals were perfect, spot-on specifications. I replaced all of the bearings with new ones from Ireland Engineering, and I checked the clearances with Plastigage. Everything was well within specs. Oil passages in crank and block were cleaned, and I had great oil pressure with my new oil pump. Even with the knock, I had good, steady, high oil pressure, clean oil, and no loss of power.

There are only a few causes for spun bearings, and since I can trust the quality of the bearings, and had good oil pressure, I can assume that it wasn't perfectly clean between the bearing and the connecting rod. Any other thoughts would be appreciated.

Now I have to turn the crank and get oversized bearings. Should I use stock ones again, or should I go to race/rally ones? Should I replace my main bearings too? The connecting rod is scored a bit, and I probably should replace it. As far as I can tell, they are NLA. Where are rods available? Do I need to get a used one and recondition it? How hard is it to match a set? Metric Mechanics has rally prepped rods, but they would be about $700+ for the set, a little more than I want to pay right now, unless it's really worth the money.

With my fresh rebuild I was putting down about 100 horses, and I had an EFI project in the works for this fall (I may have to put it off now, due to funds). I also would like to mild turbo it sometime in the future, ~200 horses, so I would like a good and stout bottom end.

Any help, consolation, parts availability information, or anything else would be greatly appreciated. Thanks.

Reuben2002

[robspeed]

I was travelling to Medford on Thursday to get some replacement sheetmetal, and I got about 150 miles when a rod knock developed. Took all day for a freind to come and get me and tow it back to Walla Walla (but now I can recite the history of Shaniko from memory). Pulled the engine on Friday and tore the bottom end down, got a spun rod bearing on cylinder 2.

What pisses me off the most is that I only have about 1500 miles on a fresh rebuild. I did the work, and since it is only the second engine I have rebuilt, I was extra careful and meticulous. The crank journals were perfect, spot-on specifications. I replaced all of the bearings with new ones from Ireland Engineering, and I checked the clearances with Plastigage. Everything was well within specs. Oil passages in crank and block were cleaned, and I had great oil pressure with my new oil pump. Even with the knock, I had good, steady, high oil pressure, clean oil, and no loss of power.

There are only a few causes for spun bearings, and since I can trust the quality of the bearings, and had good oil pressure, I can assume that it wasn't perfectly clean between the bearing and the connecting rod. Any other thoughts would be appreciated.

Now I have to turn the crank and get oversized bearings. Should I use stock ones again, or should I go to race/rally ones? Should I replace my main bearings too? The connecting rod is scored a bit, and I probably should replace it. As far as I can tell, they are NLA. Where are rods available? Do I need to get a used one and recondition it? How hard is it to match a set? Metric Mechanics has rally prepped rods, but they would be about $700+ for the set, a little more than I want to pay right now, unless it's really worth the money.

With my fresh rebuild I was putting down about 100 horses, and I had an EFI project in the works for this fall (I may have to put it off now, due to funds). I also would like to mild turbo it sometime in the future, ~200 horses, so I would like a good and stout bottom end.

Any help, consolation, parts availability information, or anything else would be greatly appreciated. Thanks.

Reuben2002

got any pics of the faulty bearing/s?? hydraulic bearings as you know never actually touch metal surfaces except from lack of oil pressure *or* foreign object getting stuck, causing the area around the object to rise (in the surface of the bearing) and *then* start to make contact. Once contact happens, heat builds, metal expands, gets stickier, goodbye motor.

its possible something fell into the crankcase that you didnt spot, it doesnt take much to destroy things. little bits of dirt can be disasterous. id be very interested to SEE the bearing in question. any heat marks or other suspicious marks???

[TobyB]

Bummer- you have my sympathies...

my last 'rebuild' is suffering ring- seating problems.

When you assembled it,

did you check the clearances?

Were your rods 'reconditioned'?

Rod bolts tight when you took it apart?

It seems really unlikely that junk in the motor

would have caused it, unless it was BIG junk,

and you'd have found that in the crank on teardown.

More likely, something was wrong in the rod tolerances- too

tight or too loose on the crank, OR too tight or too loose in the rod.

Or an oiling hole misalignment on the main bearings-

the rods get oil from the mains, through the crank.

Post some pics- different failure modes leave different traces.

t

edit- and if you can't find rods, I'm sure I can dig up a set

you can have for cheap.

[reuben2002]

I'll try to get some pics up this evening. The bearings have a dark band on the rod side, but it is smooth. On both sides of the band, they are heavily scored and show signs of metal transfer. The crank side shows normal metal-to-metal scoring, with no bands or spots.

The rods were inspected and balanced, but they weren't lightened or shot-peened. New nuts and bolts were used, and they were still tight when I pulled it down. The crank and block were both meticulously cleaned, should have been no "junk" able to cause damage. I haven't pulled the crank yet, that will be Monday, but I'm pretty sure the oil holes lined up. I used the modified main bearings from Ireland, to direct more oil flow to the rods.

[JR]

Check "Big End" for out of round condition. Also reason why engine reqired the first rebuild may provide clues.

[reuben2002]

The rod that had the spun bearing is kinda hosed, and it seems that after knock hammering it would be out of round by now anyways. I think big-end dimensions are checked on inspection, should have been good.

I rebuilt it because I cracked a head. Never overheated, I just ended up with water in the oil. I was in the middle of nowhere, so I just changed the oil every 100 miles and drove it the 500 miles back home. The engine had about 200k on it, plus runing it with water hosed the bearings (none were spun or scored, just worn out of specs), wore out the oil pump, and of course the head needed replacing. The bore was out of spec, so I had it machined to fit a set of pistons I picked up cheap (MaxSil, ~90.2mm, read my other thread about them). With all this work, and $1000 worth of parts, I was lead to believe that it should be good now, and that the pre-existing problems should have no bearing on the current situation (no pun intended). Correct me if I'm wrong though.

[trangieboy]

The 1st time you started up the engine after the rebuild,did you do anything to make sure the engine had oil pressure BEFORE it actually started up.I once saw an engine seize its bearings just winding it over on the starter trying to get oil pressure,after a rebuild.

Just wondering if some damage could have been done back then.

A good trick is to pack the oil pump with `vaseline` or `petroleum jelly`.The pump will prime straight away and the `vaseline` will melt away once the engine is warm.I like to wind the engine on the starter with plugs out till oil pressure is up.Then start.

Mal.

[reuben2002]

I primed the oil pump with oil before installing the pan by turning the sprocket by hand with the screen submerged in oil until there is oil all the way to the head. That's the way the Haynes manual says to do it. I had oil pressure right away under cranking. I also ended up cranking it a dozen or so times before it started (seems the wire to the points is kind of important). It always had good oil pressure, even at the end.

TobyB - I would be interested in a set of rods, how much do you want for them?