what happened to these main bearings?

[ryan319]

i know that we were looking for something in the range of .0015 and .0020. that's what they were supposed to be. but like i said, i didn't check them after i got the shortblock back so i don't really know exactly what they were. but i think that tighter would better explain the bearings. or i guess they could have been too loose and the crank pounded them.

when i put the motor in i primed the oil pump and had good oil at every push rod and to the turbo feed. the pressure has always been really solid, as i noted, until last week. even with that being the case, could there be an oiling problem other than the clearances? or does this definately look like an issue with the clearances? i noticed the rod bearings were wearing too but not like the mains.

 

[ryan319]

My $.02...
Too tite. A couple "what if" scenarios are coming to mind............
1. Clearances were checked B4 the coatings were applied. [Statement indicates coating used to "adjust" clearances.] Machine shop assembled the engine w/o re-checking the clearances, thus the "too tite" problem.
2. The crush/parting line clearances appear to have been wiped out, indicating the main bores could have been knocked out of round by the previous encounters with detonation.[Obviously the block was not line bored, or else the fretting would have been milled off the caps]. Once the parting line clearance is gone, the edges of the brg shells become "oil scrapers", and remove the film off the crank. It's "down hill" from there....

Time to have a "prayer meeting" w/ the machine shop gooru....

i'm pretty sure that the bearings were rechecked after the coating. the line bore was also checked and was said to be OK. it's listed on my bill that way.

your comment on the "oil scrapers" makes a lot of sense because he edges of some of the bearing look blue from heat, like they were scraping the crank.

 

[chadly]

Sorry this happened to you. I have nothing to offer but rather trying to learn.
This is the first I’ve read about “fretting”. What are you looking for that indicates fretting?

 

[johnplogii]

If it was an oiling issue the rods would have gone first, they get their oil after the mains.

 

[ryan319]

If in fact, it was line bored, the owner statement of "no detonation" is in error, & Mike's assessment is dead on....
One can look at the underside of the pistons, ring groove clearances, rod bearings, plugs, and pretty well tell if detonation is the culprit. What do they look like?
QUOTE]

the line bore was only checked and said to be OK. only one of the rod bearings was bad (#1) and it looked like the mains (like it was hot-shorted). the other five has some wear but the top part of the bearing was not pounded like it was experiencing detonation. if i detonated this motor then my scanmaster and knock gauge are broken. i religiously checked the recall on the SM after a WOT pull and the knock was always 0.0 with 02's near 800, until last week when the motor started knocking.

 

[TurboDave]

From the looks of #3 and #4 (beat completely into the wrong size), I'd have the crank runout checked really close back there also!!!

If it wasn't bent or cracked before, there's a good chance it is now.

 

[LOT]

fretting

Sorry this happened to you. I have nothing to offer but rather trying to learn.
This is the first I’ve read about “fretting”. What are you looking for that indicates fretting?

Also called "caps have been walking". In the posted pics, look @ the mating surface of the caps--where it mates to block. Looks like pitting but is actually vibration. Caused by spark knock. Kinda like taking a sledge hammer to the top of your piston.

 

[m233roller]

Ryan, I totally believe you when you state you saw no detonation, I was simply stating that from the looks of the caps there was surely some detonation. Then you said they were like that from before. I really don't see a bent crank as I caught what you originally said ( rod bearings all but one looked ok) yes it could be tweaked but I'll stand on clearance's and or line bore off. ANY GOOD machine shop would of machined those caps and done a reline bore on it or insisted on new caps. So who knows (without doing lots of checking and measuring) and being able to check and see all in person)???? I can say one thing it's not to loose as the bearings are not pounded, they are burnt up. Also .002 of the mains in these engines is not to loose. I do all mine at .002 and have NOT had one main bearing problem and I just finished building my 16th engine. Good luck and keep me posted with what you come up with.

 

[ryan319]

well i talked to the shop this morning and they said it was probably an oiling issue. which i don't understand cause i had good pressure until the pressure went and i quite driving the car.

yes i used an electric oil gauge but it told me when the pressure dropped, and its always seemed consistent so i don't think that it's the gauge.

i'll probably finish tearing the motor down this weekend to take some measurements and more pics. i hope that the NOS crank that i just bought isn't wasted but it doesn't look good. anyone have a nice shortblock laying around?

 

[thadeal4real]

find a new shop

 

[thadeal4real]

no

If it was an oiling issue the rods would have gone first, they get their oil after the mains.

not always

 

[Chuck Leeper]

"well i talked to the shop this morning and they said it was probably an oiling issue. "
Sounds like a "cop out" statement, considering they got the info via fone, and haven't actually inspected the mess....
I guess it comes down to 1 of 2 ways to "fix" it.
Bust thier chops and make them make it good.
Throw it in the trash, and go elsewhere.

I think I'd go elsewhere, as they would not be able to avoid repeating the same mistakes...

 

[chevellejoe]

I have been down this road b4. I would go to a different reputable machine shop and have them check the mains and rods. My guess is the mains are out of round bc of the wear on the sides of the bearing or too tight of clearance. If you do need to line bore the mains make sure they torque the heads on prior to machining the mains. The torque from the head they stay will distort the mains.

And from my experiance the machine shops will never admit when they did something wrong. Its always good pratice to double check the machine work prior to installation, if you have the micrometers and dial gauges to do so.

Good luck

 

[ryan319]

i got the motor apart.

 

[johnplogii]

If it was an oiling issue the rods would have gone first, they get their oil after the mains.

not always

You're saying that you can lose oil pressure & destroy the mains yet the rods still have adequate oiling?

 

[thadeal4real]

lol

You're saying that you can lose oil pressure & destroy the mains yet the rods still have adequate oiling?

no im sayn theres all kindsa oiln issues lol but really why does everyone think rods tell all they tell alot but have you ever seen a wiped out rocker shaft but rods ok? or main housing bores could be out and bent crank that will lead to "an oiling issue" but rods could still be ok there are lots of factors what if it had the wrong size main bearings but rods were correct would they go first?

well not always
ps adequate oiling thats not what i said

 

[johnplogii]

no im sayn theres all kindsa oiln issues lol but really why does everyone think rods tell all they tell alot but have you ever seen a wiped out rocker shaft but rods ok? or main housing bores could be out and bent crank that will lead to "an oiling issue" but rods could still be ok there are lots of factors what if it had the wrong size main bearings but rods were correct would they go first?

well not always
ps adequate oiling thats not what i said

Bad main bore, bent crank, wrong size bearings COULD all cause oiling issues. But whichever it was respectively would be the cause of the problem, not the oiling prob which would be the end result.

I stand by what I said, if it was an oiling issue that started it all, the rods would be worse than the mains.

 

[larrym]

I have a question I have been following this post and wonder what about contamination, could something like that be attributed to this type of wear?

 

[Alky V6]

The first that you noticed any sort of noise from the engine was at the track after some passes?
Before taking the car to the track, no noise?

What sort of oil pan are you using? Stock? Modified?

Were you able to monitor the oil pressure throughout the passes? Including during shutdown?

What fuel were you using at the track? What ignition timing setting?

What compression ratio was the engine setup with? Was the CR accurately double checked or just assumed? Was the block deck or the head surfaced? How much was taken off?

 

[turbodave231]

I think you need to have the main bores checked for Out of round and Taper. With that much cap fretting, and bearings that look that bad, It is a good bet that your main bores are NOT round.

This task requires a precision bore gauge that reads to a .0001" and a micrometer that reads to a .0001" or setting standard. A good machine shop will always check and correct this critical block dimension before any other operation is performed. All the other block machining operations should be located off the main bearing/crank centerline. If the main bores are messed up, everything else will be as well.

The main bearing bores for a Buick V6 should be:2.6870-2.6880"

You shouldn't see more than .0003-.0005" out of round and taper. Less is obviously better. If the bearing bores aren't perfect without bearings in them, They won't be right with bearings either.

Dave