spun bearing? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

68_GMC_910 · 09-14-2002, 06:41 PM

eh... I got another dumb question...

what does the term "spun bearing" refer to?

*Gee_Emm* · 09-14-2002, 07:39 PM

The term spun bearing refers to what happens when the bearing,( a thin piece of curved metal) is worn down so much in a connecting rod or crankshaft that it comes loose.

68_GMC_910 · 09-14-2002, 07:46 PM

thank you very much, Gee emm!

68_GMC_910 · 09-14-2002, 07:47 PM

oh yeah, and Jones Soda rules all!

PanelDeland · 09-14-2002, 07:55 PM

Engine bearings are actually an insert type bearing.Think of a bushing cut in half to make two half circles.One is put into the block or rod; the other goes into the cap.Each has a small tab or nub that keeps it from turning. They have a hole and usually a small groove to allow oil to feed between the bearing and crank.The pressure of the bolts clamping the cap causes the tab to keep the bearing fitted into it's half of the housing and stops it from turning.
When the bearing does turn it is called a spun bearing.It usually damages the crank and maybe the cap.There are several causes, some of which are,
1)loss of lubrication;causes the bearing to weld to crank
2)wear;bearing gets thin enough that the tab can pass it's recess and the bearing can turn
3)lack or loss of torque.
There may be some causes I haven't thought of.
Hope this makes the "spun bearing" a little more understandable.

*Gee_Emm* · 09-15-2002, 02:27 AM

Another reason could be not big enough journals being made, like in the case of my 84 s10 blazer 2.8

CoryM · 09-15-2002, 02:48 AM

Bearings are 2 halves that make up a circle that surrounds your crank journals. In a perfect world the bearing should never touch the crank because there is oil in between. However in the real world sometimes there isnt enough oil in between and they contact. It doesnt take long for the bearing to weld its self to the crank. Then the welded bearing goes for a ride and rams itself around into the other halve of the bearing. Then the engine makes awful noises and you gotta open up your wallet. Yes that is experience talking there. Often a spun bearing will destroy EVERYTHING. Sometimes the block is salvagable.
CoryM

Longhorn Man · 09-15-2002, 09:21 AM

And sometimes you can take a high nickle block with 3 spun bearings (yes...3!!) and 2 bent rods, and trade for a complete 400 small block. That's how I got the 400 that is in bloo's barn.

Michael A. K. G · 09-16-2002, 11:18 AM

You can spin other types of bearings, too.

There are two integrated ball-type bearings in the Saginaw 3-speed transmission. If the tranny were to be run dry, the balls would weld to the inner and outer races. The only way for the bearing to continue to turn would be for one of the races to break loose from its bore, and spin. Usually, it's the outer one because the inner one is pressed on tighter.

A spun bearing usually damages whatever it is installed into or on. That's usually something expensive, like a mainshaft, transmission case, axle housing, etc.

You can spin wheel bearings and differential bearings, too. I suppose you could spin the bearing caps on a U-joint, also, though I haven't heard of that happening.

09-14-2002, 06:41 PM	#1
68_GMC_910 what would Neal do? Join Date: Sep 2002 Location: Winnipeg, Manitoba, Canada Posts: 150	spun bearing? eh... I got another dumb question... what does the term "spun bearing" refer to? __________________ 1968 GMC 910 Long Step 250/3onTree 1969 Chevy C10 longfleet, 350/350

09-14-2002, 07:46 PM	#3
68_GMC_910 what would Neal do? Join Date: Sep 2002 Location: Winnipeg, Manitoba, Canada Posts: 150	thank you very much, Gee emm! __________________ 1968 GMC 910 Long Step 250/3onTree 1969 Chevy C10 longfleet, 350/350

09-14-2002, 07:47 PM	#4
68_GMC_910 what would Neal do? Join Date: Sep 2002 Location: Winnipeg, Manitoba, Canada Posts: 150	oh yeah, and Jones Soda rules all! __________________ 1968 GMC 910 Long Step 250/3onTree 1969 Chevy C10 longfleet, 350/350

09-14-2002, 07:55 PM	#5
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,992	Engine bearings are actually an insert type bearing.Think of a bushing cut in half to make two half circles.One is put into the block or rod; the other goes into the cap.Each has a small tab or nub that keeps it from turning. They have a hole and usually a small groove to allow oil to feed between the bearing and crank.The pressure of the bolts clamping the cap causes the tab to keep the bearing fitted into it's half of the housing and stops it from turning. When the bearing does turn it is called a spun bearing.It usually damages the crank and maybe the cap.There are several causes, some of which are, 1)loss of lubrication;causes the bearing to weld to crank 2)wear;bearing gets thin enough that the tab can pass it's recess and the bearing can turn 3)lack or loss of torque. There may be some causes I haven't thought of. Hope this makes the "spun bearing" a little more understandable. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

09-15-2002, 02:48 AM	#7
CoryM Registered User Join Date: Dec 1999 Location: Surrey, B.C. , Canada Posts: 874	Bearings are 2 halves that make up a circle that surrounds your crank journals. In a perfect world the bearing should never touch the crank because there is oil in between. However in the real world sometimes there isnt enough oil in between and they contact. It doesnt take long for the bearing to weld its self to the crank. Then the welded bearing goes for a ride and rams itself around into the other halve of the bearing. Then the engine makes awful noises and you gotta open up your wallet. Yes that is experience talking there. Often a spun bearing will destroy EVERYTHING. Sometimes the block is salvagable. CoryM __________________ 1970 heavy duty C-10 fleetside sport truck. Vancouver B.C. Canada http://www.geocities.com/chevroletc1070 "Take up our quarrel with the foe: To you from failing hands we throw The torch; be yours to hold it high." Lieutenant Colonel John McCrae, Canadian Army

09-14-2002, 07:39 PM	#2
Gee_Emm Account Suspended Join Date: Sep 2000 Posts: 3,991	The term spun bearing refers to what happens when the bearing,( a thin piece of curved metal) is worn down so much in a connecting rod or crankshaft that it comes loose.

09-15-2002, 02:27 AM	#6
Gee_Emm Account Suspended Join Date: Sep 2000 Posts: 3,991	Another reason could be not big enough journals being made, like in the case of my 84 s10 blazer 2.8

09-15-2002, 09:21 AM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	And sometimes you can take a high nickle block with 3 spun bearings (yes...3!!) and 2 bent rods, and trade for a complete 400 small block. That's how I got the 400 that is in bloo's barn.

09-16-2002, 11:18 AM	#9
Michael A. K. G Registered User Join Date: Jul 2002 Location: California central coast Posts: 126	You can spin other types of bearings, too. There are two integrated ball-type bearings in the Saginaw 3-speed transmission. If the tranny were to be run dry, the balls would weld to the inner and outer races. The only way for the bearing to continue to turn would be for one of the races to break loose from its bore, and spin. Usually, it's the outer one because the inner one is pressed on tighter. A spun bearing usually damages whatever it is installed into or on. That's usually something expensive, like a mainshaft, transmission case, axle housing, etc. You can spin wheel bearings and differential bearings, too. I suppose you could spin the bearing caps on a U-joint, also, though I haven't heard of that happening.



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