Guys, I've heard guys talk about a "spun" bearing in their's or other's engines, but I don't know exactly what that is. I'm not that much of a mechanic.

I never thought to look dumb by asking them....
Here I have a little bit of anonymity. ;^)

I reckon they mean a main bearing. They build their own engines, and I wonder what if anything they did wrong, or what one can do to prevent "spinning" a bearing.

Thanks!
T.

When an engine is running normally and has good oil pressure and proper clearance between the crank and the bearings......there is no metal to metal contact. The parts are riding on the oil essentially.

If that oil is lost and the metals rub it does not take long before the heat and friction causes the bearing to "spin" out of position and seize on the crank...it will quickly turn black and literally weld itself to the crank.

Once that happens major failure is gonna happen very quickly depending on power level, rpm, and numerous other things like how strong the parts are.

quote:

Originally posted by SCDIV1:
When an engine is running normally and has good oil pressure and proper clearance between the crank and the bearings......there is no metal to metal contact. The parts are riding on the oil essentially.

If that oil is lost and the metals rub it does not take long before the heat and friction causes the bearing to "spin" out of position and seize on the crank...it will quickly turn black and literally weld itself to the crank.

Once that happens major failure is gonna happen very quickly depending on power level, rpm, and numerous other things like how strong the parts are.

What he said

Minor motor. When the stars didn't align that day.
Spun the mains in the block. Block had to be sent back to have all the block saddles welded up and line bore. Not mine....







When "Everything" spins clear out of the car.

This message has been edited. Last edited by: TD3550,

Here’s hoping you never find out first hand what it means

Just wanted to add that it doesn’t have to be a main bearing, a rod bearing can spin too. That can be what a “rod knock” is, when a rod bearing spins it opens up lots of clearance and the rod knocks against the crank when it changes direction loud enough to hear it.

quote:

Originally posted by 183N:
Here’s hoping you never find out first hand what it means

Just wanted to add that it doesn’t have to be a main bearing, a rod bearing can spin too. That can be what a “rod knock” is, when a rod bearing spins it opens up lots of clearance and the rod knocks against the crank when it changes direction loud enough to hear it.

Yep
Just that description makes me cringe........

As said before when no oil in the brg it welds it to the crank and spins with it, usually its a rod or 2 on the same journal, cranks can be fixed but sometimes it takes a rod(or 2 and the block) if it goes really bad, can go from from a crank fix and some rods or a new short block, depends on what RPM it happens at...

There wasn't really a spun bearing. I just wanted to post carnage pics.

what is spun bearing ? Death to rod and most of the time to the crank. Simplest answer it s expensive biotch.

Regan,I thought that was a high dollar oil pan with "Extra" drain back holes. Lol

My old engine out of my dragster. Was on a killer run, 80lbs of oil pressure. At about 1000ft, it nosed over and felt like I hit the brakes. Just as I was pulling my foot off the gas, I heard the bang, then vibrated hard enough to blur my vision. I shut it off and coasted off the track...Holes in both sides of the oil pan. Had oil pressure until there wasn't any left in the pan to pump. Spun 7&8, broke #7 rod in half. Took a while to figure out what happened, it was the particular bearing I was running. Have another racer friend that was killing mains the same way and was running the same bearings. He had the crank manufacturer look at things and that's how he found out. Switched bearings and no more issues. Same here....

quote:

Originally posted by Tim Mitchell:
Regan,I thought that was a high dollar oil pan with "Extra" drain back holes. Lol

It drained from about 1300' to the end of the shutdown. I'm sure it delayed the final rounds of that bracket race at Hallsville Raceway till the following weekend. We actually saved the oil pan. Those heads in the pic were old Bow Tie heads that Kenneth Abbott did for me back in 1995. They flowed 413 at 800 lift. That little 565 made 950hp back in 2001.

It wasn't a CB-743 HN was it?. That decided to leave the area?. Any signs of detonation was there?. L19 only. Handling, never an issue.

This message has been edited. Last edited by: TD3550,

I was running King Hp mains, never an issue. Rods were King XP bearings. Was running them because I had mid ordered so figured they would be ok. Other racing buddy was running the same. Turns out they were delaminating then would "grab" the crank and at that point it was game over. That was my third pass on those bearings. My buddy was getting about the same, 3-5 passes before boom. King HP never an issue.

quote:

Originally posted by Coloradoracer:
I was running King Hp mains, never an issue. Rods were King XP bearings. Was running them because I had mid ordered so figured they would be ok. Other racing buddy was running the same. Turns out they were delaminating then would "grab" the crank and at that point it was game over. That was my third pass on those bearings. My buddy was getting about the same, 3-5 passes before boom. King HP never an issue.

XP as in the coated bearing?

Spun rod bearings come from a lack of bearing crush ( provided you don't have an oiling issue ).

When assembling a connecting rod, bearing crush and clamp load are critical. The correct bearing crush is achieved when there is sufficient clamp load. If there’s too little clamp load, the big end bore of the connecting rod can distort and cause premature bearing or bolt failure. Proper clamp load is achieved by stretching the fastener properly loading it to it's designed stretch.

Once the bearing looses crush it will move. If it moves even a small amount the oiling hole is partially closed which will create an oiling issue and result in the rod bearing continuing to rotate until the oiling hole is blocked. Destruction is just an instant away.

The only thing after that is the pictures you get to share on the internet...

The word “spun” comes from the insert, called the bearing, actually turning in the bore of the block main or connecting rod big end. When happy, the insert is kept from spinning by being compressed slightly in the bore and with an alignment tab. When the insert is being destroyed, as described above, it over heats, liberates metal and is permanently damaged to the point it starts to “spin” in the bore. At around that point the crank pin is overheated and damaged. Frictional forces increase dramatically to the point a rod or crank will fail and fly apart, if not caught.

quote:

Originally posted by adv ET 266:
The word “spun” comes from the insert, called the bearing, actually turning in the bore of the block main or connecting rod big end. When happy, the insert is kept from spinning by being compressed slightly in the bore and with an alignment tab. When the insert is being destroyed, as described above, it over heats, liberates metal and is permanently damaged to the point it starts to “spin” in the bore. At around that point the crank pin is overheated and damaged. Frictional forces increase dramatically to the point a rod or crank will fail and fly apart, if not caught.

This exactly. A few years back I learned the hard way that a dragster needs a billet oil pump. At about 700’ into a run it felt like the engine “tightened up” and nosed over. I immediately took my foot out of it and shut it off. When I took it apart the melling pump pickup was laying in the pan. #1 journal on the crank got hot but luckily I clicked it off before any bearings spun. Had to turn the rod journals .010, put it back together and the crank broke at the first journal 60 passes later. No doubt due to being turned.

Now all three of our engines have Moroso billet oil pumps.