Update: Spun mains
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,635
Likes: 0
From: Union Ontario
Update: Spun mains
I pulled all of my main caps tonight and found the three center bearings spun. The two outside have a few scratches but aren't that bad but would have eventually spun.
The crank is shot, the groves on it are at some points 1/32-3/64" deep.
Something must have broke off in the engine because the bearings are tore up really good.
I guess I'll bolt it back up, and start tearing into car starting the restoration.
I'll post some pictures tomorrow when I take the camera back to work.
The crank is shot, the groves on it are at some points 1/32-3/64" deep.
Something must have broke off in the engine because the bearings are tore up really good.
I guess I'll bolt it back up, and start tearing into car starting the restoration.
I'll post some pictures tomorrow when I take the camera back to work.
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
Re: Update: Spun mains (paul79)
Tell us neophytes how a bearing spins on the crankshaft! And why. I am sure many Members would be interested.
During high school, I owned a '57 Pontiac with a 283Cu.In.
(Note: in Canada Pontiacs had a Chevy powertrain)
I knew the mains were getting quite loose. If you were accelerating, then let off the gas completely, it would gain about 10-15 lbs oil pressure.
When you let off, the crank would lift in the mains and restrict the flow of oil.
Well, one day there was a screech from the engine and a loss of oil pressure.
Upon inspection, one of the mains had starved for oil and the crank and the bearing actually touched each other. The resulting friction caused the bearing to weld itself to the crank. That became a stronger force than the little notches that hold the bearings in place and the two halfs of the bearing then spun in the block because they were now attached to the crank.
If the block journal is scored at all, then the block will need to be align bored.
You can also spun a rod bearing. Excessive bearing wear, loss of oil protection equals bearing contact with the crank. Disaster follows.
Hope this helps.
Barry
[Modified by Barry's70LT1, 11:51 AM 10/11/2002]
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,635
Likes: 0
From: Union Ontario
Re: Update: Spun mains (paul79)
Paul, basically you'll spin a bearing when the friction between the crankshaft and bearing is higher than between the bearing and the bearing journal. This means that it is easier to sping the bearings than to rotate the crankshaft inside the bearing As close as I can figure out either my middle main got oil starved and sent shrapnel through my engine destroying the other mains or something got in my engine( some foreign objects or objects)
Pictures to follow
Pictures to follow
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Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,635
Likes: 0
From: Union Ontario
Re: Update: Spun mains (MotorHead)
I have personally thrown 50,000 MILES( not km's) on the motor since I've owned it.
I don't know how many more than that before I owned it. But I heard before me they were accrued a 1/4 mile at a time.
[Modified by MikeC, 10:20 AM 10/11/2002]
I don't know how many more than that before I owned it. But I heard before me they were accrued a 1/4 mile at a time.
[Modified by MikeC, 10:20 AM 10/11/2002]
Le Mans Master
Joined: Aug 2000
Posts: 6,362
Likes: 7
From: Brazos TX
Cruise-In IV Veteran
Cruise-In V Veteran
Re: Update: Spun mains (MikeC)
Wow, bad deal. Those grooves in the main cap don't look good. I wonder if they are too deep to clean up with an align bore of the bearing journals.
