Thread: bearing life

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I remember reading Smokey Yunick's explanation about spun bearings. It's usually caused from detonation.

He explained it this way: If you lay a bearing half on the bench and beat on the center of it with a ball pien hammer, the ends of the shell will curl up toward each other. He said that is what happens when the motor detonates, the crankpin hammers the bearing shell, curling up the ends and wiping all the oil off the crankpin. Smokey worked with the bearing companies to develop a bearing with a chamfer at the edges of the shells so that as they curled up, there would still be some clearance between the edge of the shell and the crankpin.

Maybe there are special bearings with a larger chamfer on them. I've never seen the need for them and like Bryan, I've never spun a bearing. I just make sure the motor doesn't detonate.

Originally posted by techinspector1
I remember reading Smokey Yunick's explanation about spun bearings. It's usually caused from detonation.

He explained it this way: If you lay a bearing half on the bench and beat on the center of it with a ball pien hammer, the ends of the shell will curl up toward each other. He said that is what happens when the motor detonates, the crankpin hammers the bearing shell, curling up the ends and wiping all the oil off the crankpin. Smokey worked with the bearing companies to develop a bearing with a chamfer at the edges of the shells so that as they curled up, there would still be some clearance between the edge of the shell and the crankpin.

Maybe there are special bearings with a larger chamfer on them. I've never seen the need for them and like Bryan, I've never spun a bearing. I just make sure the motor doesn't detonate.

do you mean eccentricity less bearing thickness at the haves and a strait wall bearing the same all the way round and 5and7 miss firing . gm not so good ideal. that way i like the 4 -7 swap and use them

"less bearing thickness at the haves"

yes, take a look at a half, mic it at the edges, you'll find it is thinner.

Originally posted by Bryan TTM
Clevite makes a good bearing...in all my nitrous motors i would scotchbrite the surface before installing...if i had to go into the engine i usually changed em but they always looked good..i gave em to my friends so they werent wasted...aluminum rods will cushion the blow...i've had em make over 200 passes with 1900 or so hp...just fine...are your rod ends egg shaped

YOU SCOTCHBRITED THE BEARINGS.WON'T THIS TAKE MATERIAL OFF THE BEARINGS?HOW DO YOU KNOW IF YOU RE-MOVE IT EVENLY AND HOW MUCH DID YOU REMOVE?HOW ARE YOU ABLE TO PUT A FINISH ON THE BEARINGS AS SMOOTH AS THE MANUFACTURE DID?WHY DOES'NT THE MANUFACTURE OF THE BEARING DO THIS?DO YOU DO THIS BECAUSE THE ENGINE IS TO TIGHT?WHY NOT POLISH THE CRANK INSTEAD?

Originally posted by techinspector1
"less bearing thickness at the haves"

yes, take a look at a half, mic it at the edges, you'll find it is thinner.

i am not trying to be a ass yes i know just trying to help the word for this eccentricy and a strate bearing wall is a delta wall and chamfered type bearings are call h type for bigger fillet radii and the old scothbrite the bearing was a old trick guy did not like the flash coat on the new bearing and take it off .WHY ?? this is why and have see it the flash will come off and it builds were it can get the thinner parts of the bearings now it will start working on the bearing not good. it will in time take the crank out. in the old day they did not have H bearing. the there is no flash coating on H bearings so no need to scoth them .a that is why i said i do not like stock feds on mild to race engines they have a very heavy flash on them and it dose and will move .THE FLASH is put on for the bearing for to take more or less brake in and they say. and is harder then the bearing babbit it self . there this so much more on this and many guys do what works for them . this my opinion i think about this stuff alot

Pat, I wasn't talking about the side of the bearing that runs against the crank fillet, I was talking about the edges where the two halves butt together. That's where they curl up and wipe the lube off the pin.

"i think about this stuff alot"

You need a wife to take your mind off all this bearing stuff

Originally posted by techinspector1
Pat, I wasn't talking about the side of the bearing that runs against the crank fillet, I was talking about the edges where the two halves butt together. That's where they curl up and wipe the lube off the pin.

"i think about this stuff alot"

You need a wife to take your mind off all this bearing stuff

yes i did get that . but wanted to make shure some new guy did not get confused.i know how to keep a engine happy not to shure how to make a women happy all the time ok 1/2 the time?? ok i wound take two hours out of a dayok i think i will think more about bearings and talk to my dog

Do you mean when you plastigage it. And the side to side clearence was what the gm book said i can't think of it right now but I will check. I never checked the crush I just asumed the rods where good and and they are stock gm 5.7 rods. I have rebuilt motors before but where never run hard so the whole high rpm performance stuff is new to me. I have never had to get that technicle with a motor. I know now that I need to on my next
build. So sorry if I ask so much but I realy apresheate it.

No problem Joe, all of us are eager to help a fellow racer. The best plan is to make certain that whoever sizes the big ends of the rods uses the mimimum spec (tight) and make certain the motor is not detonating.

Is'nt detonating when the engine fires or am i mistaken.

Originally posted by joe bogger
Do you mean when you plastigage it. And the side to side clearence was what the gm book said i can't think of it right now but I will check. I never checked the crush I just asumed the rods where good and and they are stock gm 5.7 rods. I have rebuilt motors before but where never run hard so the whole high rpm performance stuff is new to me. I have never had to get that technicle with a motor. I know now that I need to on my next
build. So sorry if I ask so much but I realy apresheate it.

the bore of the rod needs to be check with a bore gauges. check to see if it was round and to size this give you crush if they were stock rod not check. and stock gm bolt this may be it .this stuff work good all day in stock stuff .but has to be rigth on mild to race stuff

Originally posted by joe bogger
Is'nt detonating when the engine fires or am i mistaken.

http://en.wikipedia.org/wiki/Detonat...bustion_engine

http://www.stanford.edu/~bmoses/knock.html

So it is spark knock. When you don't have high enough octane for your compression.

So no bearing will make a stock rod hold up or dose it just have to be exactly right in order to work.

this will be it for me on this .i will try to take you thru it the way i think?? stock rods will not stay round and not many rod s out there will WHY?? the bolts are at the sides of the rod and cap .a stock rod with a stock piston at low rpm will stay round you hope.BUT stock rod with a hp piston some times very heavy and hi rpm now the rod has more weigh on one end. swing a empty bucket a round with your arm .now fill it with lead if you can swing it some things may happen your arm may fall off. or the strap on the bucket. let say it.s all good .now it time to turn it up much faster rpm .now the weigh is working to find the weak link and it will in time .the weak link is were the rod halves are. now if the rod bolts hold .what will happen to the rod?? it will and dose not stay round it will go egg shape more eccentricity and will take out the crank so you do not want a round bearing it will grab the crank at the halves and you do not want full contact on the bearing there needs to be room for oil to ramp the bearing off the crank.what will happen is the bolts go past there use and fail?? the rod bearing crush is lost and the bearing will fail .the cap on the rod may be to thin and can not take the rpm and the weigh and fail look at the stock 460 ford rod very scary. here are some thing and there is more but this is it for me