dallasyoung

Hey sorry to sound stupid but I read a post and someone said he was scared to go WOT b/c he might spin a bearing. What does that mean? Is it the thrust bearing? If so...what is/does the thrust bearing do? TIA!

rotten

To spin a bearing means when you lose lubrication on the crank and instead of the crank spinning inside the bearing, the bearing actually spins WITH the crank.

dallasyoung

The crank spins inside a bearing? Whats this bearing called? inform me! THANKS!

bartek_b

WTF?? no, the bearing gets attached to the CRANK and spins WITH the crank.

just like ROtten said


[Modified by mugen85r, 12:53 AM 2/3/2003]

DC2Monster

it means put some damn oil in that motor!

HEAD

it could also mean there is not enough bearing clearence. no amount of oil can help that. there is a saying when building a engine the circle track guys use
"to loose, you know it, to tight, everyone knows it!"

b19coupe

Engine main and rod bearings are half circles of a soft metal that encircle the rod and main journals of the crankshaft. There is one on top and one on the bottom of each journal. Usually when a bearing spins, it is a rod bearing, and the engine will develope a knocking sound. Get an engine repair manual and read up on this stuff if you really want to know about it. Pictures and text together would help you to understand better.

B18EG6

Off of Sonny's website:







hope this makes it more clear..

dallasyoung

In the first pic, those "U" looking things, what are those?

harryg

That's the main bearing.

rotten

Those are the main bearings... notice how they sit on the block, and the crank sits on them. They are supposed to 'stick' to the block, and let the crank move with the least amount of resistance as is possible. The problem is sometimes if the bearings are too big, or aren't getting proper lubrication they stick to the crank, which causes major damage.

Thrust bearings are similar except they provide a frictionless surface when the crank is pushed horizontally instead of spinning. Basically prevents side-to-side crank-> block friction.

-k

_Endless_

so what kind of major damage will the engine have if you spin a bearing? i read from above post that you'll hear a knocking sound, what happens after the knocking sound? will the damage happen right away when you spun a bearing?

MotorMatrix.com

WTF are you talking about?? the bearing sits in place in the mains and the crank spins on a thin layer of oil inside of the bearing.

SupaTegRS

LMAO....0wned...hehehehe

B18EG6

Im pretty sure he knew how the bearings worked, I think he was referring to the title "What does "spin a bearing" mean" In which case, the bearings would indeed spin with the crank.

MotorMatrix.com

dallasyoung

Ok, so while the crank is spinning, the "U" (main bearings) stay there while the crank moves/spins?

DaiJekBok

Yes. The bearings stay in place unless that thin layer of oil disappears, in which case they spin WITH the crank, hence "spinning a bearing" and hence causing you much anger and frustration.

bigTom

no they dont spin with the crank... the bearings will also stay seated with the in the cap/block or the cap/rod... when u spin a bearing what it essentially does it get thinner... now u have a gap so everytime the crank rotates u now hear a "knocking noise" which is lets say if u spin a rod bearing... its the rod actually bouncing up and down on the crank as it spins

IntegD

so would u indeed find graphite or metal shavings in the oil if you drained it if you spun a bearing?? Ive replaced my mains and rods twice on my two rebuilds and my buddies car is making some sort of knocking. I cant decipher if its a bearing or a vibration. Is there any way to test to see if its a bearing without taking it apart??

cvcpower

Okay so wait that bearing doesn't look like what I expect a bearing to look like. Don't bearings have little ***** in them? And then the ***** make is so it's like sliding on ice, less friction and whatnot? Or am I just retarded? Dang i probably shouldn't have added that last part, perfect set up eh?

TREVER

there are many types of bearings

ball bearings the kind with the *****
tapr roller etc.
main/ crank bearings are just half circle shells that rods/ cranks ride on (with oil)
honda uses cam bearings that aren't even there. it's just an aluminun bore.

Wes V

Oh my god; here I go on a long post.

Rod and crank bearings are a "half shell" solid bearing. They can NOT be a roller bearing due to the fact that you couldn't install them on the crankshaft. The only time that I can think of a roller bearing used on a crankshaft is in very high RPM (motorcycle) engines.

The bearing is made of hard metal and has a very soft thin metal surface that comes in contact with the crankshaft (engine turned off and no oil pressure). When the engine is running and oil pressure is up, the crank doesn't touch the bearings, but floats on a thin film of oil. If the gap between the bearings and the crankshaft is too small, then they make contact and start wearing out and get REAL hot. (part of the function of the oil is to carry off heat!!) If the gap is too large, then the oil can't retain the film surface and you get back into the crankshaft coming in contact with the bearing surface.

As to what keeps the bearing shells from rotating in the block (or the rods), you should look at the photo that is at the top of this string (how do people come up with these photos?) and look at the bearing on the left.

There are two things that keep the bearings from rotating (until it hits the fan).

The first has to deal with a small "tang" or flange (or "key") that is on all bearings of this type. Look real close at the lower edge of the bearing shell on the left. There is a small section of the shell that sticks out. This fits into a slot cut into the block (or cap). If we are talking about the shell that is in the "cap", then the end of this tang bears against the block surface. It's this shoulder that prevents the bearing from rotating and isn't all that "solid" due to the fact that the block (and caps) are soft aluminum.

The other thing that keeps the bearing shells from rotating is that they are too big for the holes that they are in. I know this sounds wierd! When you place the bearing shell into the block (while putting the engine together) you whould notice that the ends of the shell stick out (above) the block surface. This is also true on the caps. As a result, when the caps are torqued down, the total bearing is crushed down and held tight. It's much like when putting together a Chevy V8 and have to hammer in the cam bearings. If the engine was line bored too much, then this compression wouldn't be enough. (to line bore correctly, first material is taken off the block or caps to make the hole smaller, then the hole is machined back to the correct diameter.

A "spun bearing" is just what the name implies. The bearing shell rotates within the block (or rod). I believe that most causes can be linked to an oil problem. That oil problem could be a loss of oil pressure or the bearing gap clearance being wrong (just wearing out).

When a bearing goes bad, the temperature can get so hot that the bearing fuses to the crank and trashes it. The spun bearing also trashes the surface of the block (and cap) that it sits in. Line-boring (if done correctly!) can solve the diameter problem, but not provide a clean surface for the bearing "tang" (key) to bear on.

Any time that you take an engine apart (or are pulling the caps to check for wear on an engine you are thinking of buying) you should look at the bearing surfaces.

Any grooves or little "specks" of metal imbedded in the bearing surface could indicate trash flowing through the oil system at one time.

If you notice that the bearing surface appears to worn away, it's a sign of high milage. Put in new bearings. Much like brake shoes, the shoes wear out faster than the drum and if you don't wear them down to "metal-to-metal" contact, all you normally have to do is replace the shoe.

KEEP IN MIND that bearings come in different sizes (for any one engine) and that not all of them may be the same (particularly if it's been re-machined). There should be the "size" indicated on the surface of the bearing shell that comes in contact with the block. If you are getting new ones and have not machined the crankshaft, make sure that you use the correct size and put them in the correct location. (I don't know how Honda tags bearing shells)

As an added note; as RPM goes up, the required oil pressure to keep the bearings working correctly also goes up. I don't remember the "rate".

Wes Vann


[Modified by Wes V, 9:29 AM 2/8/2003]

GZERO

Wasn't it around 10 PSi for every 1K RPM?

Wes V

That 10 PSI for each additional 1K RPM sounds correct. I wasn't sure and didn't want to throw it out.

Wes Vann