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Old 10-22-2009, 07:22 PM
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Bearing help

I have a 383 SBC that was in a wreck several months ago. After reassembling the engine, it developed a vibration around 2500-3000 RPM's. Suspecting the crank, I took the engine out and these are what the upper bearing halves look like. Do the bearings look like there is a vibration, or this wear normal? Engine has approximately 300 or so miles on it. Oil pressure cold at idle was ~60 PSI, and when hot it would get down to 40 PSI at idle. Steadily increased as RPM did.






Thanks for the help.

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Old 10-22-2009, 07:27 PM
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I don't like the way the mains look, especially the first picture. Have you had the crank checked?

Vince
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Old 10-22-2009, 07:37 PM
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Quote:
Originally Posted by 302 Z28
I don't like the way the mains look, especially the first picture. Have you had the crank checked?

Vince
No, I have not yet, but the crank is out. Does the wear look like it's caused from vibration?
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Old 10-22-2009, 07:57 PM
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Little bit of background:

I have checked for runout at the rear/front of the crank, and there is none. Maybe .001", but probably not even that much. After the wreck, I dropped the engine back in (after replacing all broken parts) and hoped for the best. Probably not the smartest thing to do, but it's all I could afford at the time. I have put probably around 100-150 miles on it since, and this is the first time it has been out since then (April). No oil pressure issues. Nice and steady at all RPM ranges. Running a Melling HV oil pump. Could that be masking an oil pressure issue?

This is my first engine. Could the bearing wear be caused by improper tolerance? Too tight? Looks like heat marks. But, I'm no expert.

Thanks.
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Old 10-22-2009, 08:55 PM
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Possibly something bent or out of balance.
Bearing Problem ID. >> http://www.engineparts.com/publications/CL77-3-402.pdf
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Old 10-22-2009, 11:07 PM
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Is it worth even trying to fix this? Pretty bummed right now, really don't know what to do. I spent literally over a year building this and am having a tough time with this. Very meticulously researching and putting it together, measuring, re-measuring..you get the idea.

Last edited by mrdreex; 10-23-2009 at 12:22 AM.
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Old 10-23-2009, 05:55 AM
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oil

It's so hard to tell by pictures.

I think what you are seeing on the mains is the factory coating that will dis-color the bearings. I have some brand new in the box that look exactly like that.

Post some pictures of the mains on the crank.


Back to the accident, what happened and what parts of the engine were hit in the accident.

Is this a internal or external balance crank???


Keith
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Old 10-23-2009, 06:27 AM
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Quote:
Originally Posted by k-star
It's so hard to tell by pictures.

I think what you are seeing on the mains is the factory coating that will dis-color the bearings. I have some brand new in the box that look exactly like that.

Post some pictures of the mains on the crank.


Back to the accident, what happened and what parts of the engine were hit in the accident.

Is this a internal or external balance crank???


Keith
Internally balanced.

The actual engine was not hit during the accident. It was a frontal collision with a telephone pole that hit right between the passenger side a-arm and motor mount. Everything up front (electric water pump, alternator, pulleys, balancer) were damaged. The other damage occurred at the back of the block. When it hit, it split the bellhousing (scatter plate) from the block at the two upper most mounts, causing the block to 'shard' around the two upper bolt-holes. It did not crack through the block.

When the car hit, the engine crossmember came upwards, forcing its way into the oil pan and I believe is the cause of why my balancer sheared off. It cracked the balancer hub and sheared off the keyway into two pieces. There was a crank throw imprint in the bottom of the oil pan. I cannot find any damage to the counterweights, but the pan had a windage tray and it was eaten alive. The metal mesh was all tangled inside of (I think) the number 3 rod and bolt. There was a slight nick on one of the rod bolts on #3, but it wasn't deformed to the point I couldn't get a socket around it.

The transmission was a Super T-10, but the only thing hurt there was the case. The mainshaft did not bend and I actually replaced the tail case and put it back in. Driveshaft came out and put a couple dents in it, and one of the axle tubes in my rear came out (bent axle, come to find out later).

EDIT: I will be re-checking the main bearing clearances tonight and I will get some pictures of the crank and the journals. If it were an oil starvation issue, what would the crank journals look like? They still look polished and clean like they did when I put it in the first time.

Edit 2: Here are some pics of the lower bearing halves. I don't remember which ones went where, but I think they're all there.






Last edited by mrdreex; 10-23-2009 at 06:44 AM.
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Old 10-23-2009, 07:39 AM
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From your description of the accident I would say it's a fair assumption that your crankshaft is toast.

Vince
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Old 10-23-2009, 07:47 AM
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engine

Quote:
Originally Posted by 302 Z28
From your description of the accident I would say it's a fair assumption that your crankshaft is toast.

Vince
I would also say the same thing, at the very least i'll bet the snout is bent.


Keith
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Old 10-23-2009, 08:15 AM
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Wouldn't there be an excessive amount of runout though? I measured for it at the rear, front, and the middle three main journals but there was none. Also, wouldn't the main bearings looked chewed up a bit more? I did run it for 100 miles or so.
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Old 10-23-2009, 08:46 AM
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crank

Not if the snout is bent.

I had a LG 327 crank that was bent on the snout .020" and all the mains were less then .0005" for run-out.

Also in light of the accident description, check the flange at the rear of the crank for run-out also.


Keith
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Old 10-23-2009, 08:56 AM
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Quote:
Originally Posted by k-star
Not if the snout is bent.

I had a LG 327 crank that was bent on the snout .020" and all the mains were less then .0005" for run-out.

Also in light of the accident description, check the flange at the rear of the crank for run-out also.


Keith
I checked for runout at the tip of the snout at the front, and there was MAYBE .001" of runout. I also checked at the rear flywheel mounting flange on both the flat mounting flange and the outer ring. Both came back to less than .001". If there were any other obvious signs of a bent crank, I would be all over planning my next build, but this just doesn't seem like it's bent. Of course, it's all subjective. I'm no machinist.

Thanks Keith.
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Old 10-23-2009, 09:01 AM
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crank

I would probably spin it in a crank grinder just to see if anything shows up, and have it wet magged for cracks.


It sounds like the crank is ok, but with all the damage you described i would be looking real close at it.


Did you use the same T-10 that was in the accident???

Keith
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Old 10-23-2009, 09:08 AM
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Quote:
Originally Posted by k-star
I would probably spin it in a crank grinder just to see if anything shows up, and have it wet magged for cracks.


It sounds like the crank is ok, but with all the damage you described i would be looking real close at it.


Did you use the same T-10 that was in the accident???

Keith
I will probably take it to a shop around here to get it wet magged, etc. after I check the clearances tonight if everything checks out OK clearance wise.

I originally used the same Super T-10, just replacing the tailcase and welding on the broken mounting tab, inspecting the gears, etc. It was toast, second gear was not available when up shifting, and third was toast after a while. I sold it and bought a Magnesium cased circle track tranny (G-Force case with stock gears).

Last edited by mrdreex; 10-23-2009 at 09:13 AM.
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