Spun Bearing

[Space Cowboy]

Anyone have any idea as to what would possibly cause a piston bearing to spin out of place?

Thanks

 

[gmjunkie]

Anyone have any idea as to what would possibly cause a piston bearing to spin out of place?

Thanks

A lot of thing's!! Lack of Lubrication come's to mind!! What Hopin?? :confused Thay usly don't just spin Idling!! Tell us more!! junk!!

 

[Vettehead Mikey]

Pistons have bearings?

 

[gmjunkie]

Pistons have bearings?

Axley I think the rod duz!! This is why we need to know more!! Just a thought,may the piston's Just ain't a Pixx'n!! We have to Know More!! :W :W junk!!

 

[waterboy1976]

wrong size.......... clearances wrong.......crank turned down too far.......

thats sucks but I know the feeling...after 2 years and 427 miles I broke a valve spring...not as bad as a spunbearing but I know how bad it sucks...

 

[Rowdy1]

Lots Of Things..........

You have main bearings on the crankshaft and rod bearings on the connecting rods. You also have cam bearings for the camshaft, how do you know what bearing is spun? Oil pump failure, over reving, lack of oil pressure can cause bearing failure. How many miles on the engine?

 

[Space Cowboy]

I was referring to piston rod bearings folks. Sorry for not being specific.

Rowdy - So far... only about 700 break in miles.

 

[norvalwilhelm]

If you push a motor before the oil is hot you run the risk of spinning a bearing. When starting a cold engine bring the oil temperature up before pushing the motor.
Cold motors pushed too hard spin bearings.

 

[Space Cowboy]

norvalwilhelm,

Do you mean 'pushed' as in punching up the rpm's to say 6000?

 

[67HEAVEN]

Yes.

 

[Space Cowboy]

That's what I was afraid of. The guy (a friend) that has done my restore and engine swap out "flexed" the engines muscle the day I drove it home. I would be almost willing to put some money down that it wasn't warmed up yet. He was showing the car off to someone else in the garage.

Question... why would I not have a problem until 90 miles down the road though? Would we have not heard something right away?

Thanks

 

[gmjunkie]

That's what I was afraid of. The guy (a friend) that has done my restore and engine swap out "flexed" the engines muscle the day I drove it home. I would be almost willing to put some money down that it wasn't warmed up yet. He was showing the car off to someone else in the garage.

Question... why would I not have a problem until 90 miles down the road though? Would we have not heard something right away?

Thanks

Not Allway's,But I wouldn't Rap any eng.without a load on it!,(Warm or Cold)much less a Freash one Cold!! What a Boner Head!! I'd Whip WOOOOO'WEE Knot's on his Head!!ad Some people don't need to be a Technician!! :crazy junk!!

 

[norvalwilhelm]

That's what I was afraid of. The guy (a friend) that has done my restore and engine swap out "flexed" the engines muscle the day I drove it home. I would be almost willing to put some money down that it wasn't warmed up yet. He was showing the car off to someone else in the garage.

Question... why would I not have a problem until 90 miles down the road though? Would we have not heard something right away?

Thanks

Mileage has no effect on pushing a cold motor. When the oil is cold it doesn't flow right through the bearings and actually grabs the bearing causing it to rotate.
I always, always wait until I see the oil pressure dropping due to heat before bushing it. I have learned the hard way. I have lost bearings twice on pushing the cold motor. Driving a few miles down the road is NOT warming up the oil enough.

 

[1995 RedVette]

Our C4's have a digital oil temp guage and an analog oil pressure guage. I have noticed that the oil pressure doesn't start to drop off until the oil has reached about 180. Depending on the outside temperature, that can take several mins longer than the coolant does to reach the same temp.

I too subscribe to novral's school of thought. I always wait until the oil pressure drops before I lay into it. Waiting until the engine warms up is also easier on water pumps. The pump doesn't have to pump against a closed thermostat.

Brett

 

[Space Cowboy]

Your right gmjunkie... he's a real boner head! Being that we haven't pull the engine back out yet to inspect it, I don't want to make any rash accusations. If it is in fact a spun bearing, I'm gonna come down on him like a lead brick.

 

[USNA1969]

Being a noobie, I've never heard of a spun bearing. What does that sound like?

 

[gmjunkie]

Being a noobie, I've never heard of a spun bearing. What does that sound like?

Thay come in all Sound's But that Deep thud that will turn in to that Deep Thrash will let ya know!! Can start out as a lite Tic,(like a hydro lifter) But Lower in eng.!!! Not on Top! junk!!

 

[Greg Gore]

Reason for Spun Bearings

If the engine was recently rebuilt something was not right if a bearing failed. Bearings that are properly installed in straight round correct size housing bores with the correct fastener torque (bolt stretch- clamp load) running on straight round correct size journals within range of recommended operating clearances with correct surface finish and with sufficient clean lubrication at correct pressures will not fail if the engine is operated within recommended engine RPM limits. It is also possible an inexperienced assembler nicked the journals with a rod stud while not being careful enough pushing the piston-rod assemblies in place. This could possibly be determined by removing other rod caps to see if other rod bearings have scoring which would have also eventually failed. Unfortunately in the engine rebuilding business "rebuilt" has the same connotation as "restored" does in the car business which means the finished quality is usually the result of a shop's capability and experience and how well the shop is equipped which can vary significantly. It is extremely important to get engine work performed by someone who is properly equipped, trained and experienced with a good reputation. Problems such as this one are the usual result of shopping for the lowest price or not looking and asking around enough. Folks who know what they are doing with your engine know what their time is worth and you should not expect the lowest price but you should expect to get back a reliable engine that performs properly.

Regards, Greg

 

[Space Cowboy]

USNA1969, gmjunkie has nailed the sound... definitely a deep thud sound.

gmjunkie, I'm being told by a few (GM Certified Mechanics) that winding out the engine (without a load) shouldn't have caused a bearing to spin out... even at a somewhat cold temp. Yes, not a good practice, but leads to something else causing the issue such as something not being installed correctly on the build.

 

[gmjunkie]

USNA1969, gmjunkie has nailed the sound... definitely a deep thud sound.

gmjunkie, I'm being told by a few (GM Certified Mechanics) that winding out the engine (without a load) shouldn't have caused a bearing to spin out... even at a somewhat cold temp. Yes, not a good practice, but leads to something else causing the issue such as something not being installed correctly on the build.

Depend's on how tite eng. was set up!! It's not the Rap up that will do it it's the comeing back down Quick!! Rod and main bearing's Have a little tab that lock's into rod and cap, and if tite and cold(oil not flowing free yet) When rapping up the piston's are pushing crank,and when coming down crank is pushing piston's!! Deffernt stress on Bearing's and can Shear of Little tab in Bearing!! Hard on Timeing Chains Too!! And yes I agree with ( Greg ) on All of his post and must be very carefull and not damage crank journal!! When rebuilding a eng. I use all new Head,Rod, and Main Bolts!! Along with Fly wheel and pressure plate or flex plate Bolts!! You just don't know how far they'v been Stressed!! ( I hold a Certifcate or 2 myself!!) junk!!