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Discussion Starter #1
Hi Everyone,
What do you guys think of the way this bearing looks? it's the only one i've takin off so far. Is that normal discoloring or do they need to be replaced also? I'm going through the motor after finding the upper timing gear had desintagrated. the black line I put in shows where the bearing changes color from left to right, silver/gold. that's the best picture I could get of it.
Thanks.


 

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You need a better clear close up but from your description if it gets to gold base layer the bearing is "wiped".
 

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Hi,

I agree with Paul it doesnt look to good to me either.

Is this the same engine that broke the sprocket teeth?

I was kinda wondering back then if maybe the thrust brg had failed. I would take look at the thrust surface of the crank and the the brg.. If the the thrust is gone it have let the crank move to far forward and put the sprocket in such a bind it sheared the teeth.

I have seen many engines that had similar problems. Sometimes they will actually cut a hole in the timing cover. Might be worth looking at. Just a guess.


Good luck.

Jeff
 

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stock z/28 said:
Hi,

I agree with Paul it doesnt look to good to me either.

Is this the same engine that broke the sprocket teeth?

I was kinda wondering back then if maybe the thrust brg had failed. I would take look at the thrust surface of the crank and the the brg.. If the the thrust is gone it have let the crank move to far forward and put the sprocket in such a bind it sheared the teeth.

I have seen many engines that had similar problems. Sometimes they will actually cut a hole in the timing cover. Might be worth looking at. Just a guess.


Good luck.

Jeff
That makes more sense to me than the teeth mysteriously falling off. Good point!



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good catch! I completely forgot this was the one with the broken gear teeth.
 

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For a better pic, try a contrasting background, and 'playing' with the lighting and camera angle.
 

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Scotchbrite is highly abrasive and will wipe off the fine layers on the bearings. It leaves fine abrasive particles and should not be used on engine parts.
I think we had a posting or link warning about it somewhere.
 

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Is the bearing surface copper colored?

If so... I've never seen one so thoughly wiped liek that!

heh, i wonder if some redneck had some .010 under bearings and used a brake cylnder hone to resize them! :D just joking
 

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The engine is out and torn down...... bearings are not expensive at this point..... I vote replace.
 

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I have been thinking about the tooth failure and I was wondering how far would the crank move or how far does it have to move to bind up the cam sprocket?

novaracer1: Pull the thrust bearing and take some pictures or better yet, measure the crank end play before you take it completely apart. I think this would be an informative exersize for a failure diagnosis.
 

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Hi,

Just my opinion, but if you have a forward thrust control on the cam sprocket, like a cam button and a fairly tight timing chain assembly, the crank would not have to move very far forward to put the chain in a fairly severe bind. Camshaft load would probably also be a factor.

As far as the thrust brg goes, I normally see much more wear in the crank thrust flange than the brg itself.

I agree that I would check end play. If the rear main cap does not have dowel pin aligning it to the block ( I personally don't care for the dowel type ) I would check end play with the cap off, and the properly install the cap and recheck. I do this on all engines that I assemble, and it can be a source of problems.

If it does have a thrust problem I may have a couple suggestions, if anybody cares. If its OK it makes no sense to mention it now.


Rember just my opinion guys.

Good luck
Jeff
 

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I have a question about this more in the camshaft area. I have been told the reason for the twisted gears on the distributor and camshaft is to pull the camshaft rearward. The camshaft timing gear has a thrust plate on it that rubs against the block.
I ask this because his car uses a thrust bushing on the front that should keep the camshaft from moving forward. Those are normally ran with roller camshafts to keep the camshaft from moving forward and the thrust plate on the upper gear along with the preload from the distributor gear keeps it tight against the block.
If the rear freeze plug was driven in to far could it stop the camshaft from seating against the thrust surface? That could throw the aligment of the lower gear and upper gear. The balancer holds the lower gear in place correct?
Am I way off on all these random thoughts?
 

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I was thinking a misalignment of the sprockets during the build too. If you are using a flat tappet cam and there is no thrust button can't the cam move forward a pretty good bit?
 

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Discussion Starter #16
Wow I havn't been watching this thread because I only got one answer for a while there. I took like ten pics with different lighting and angles, and that one was the best I could get. I got some local guy to look at them, anyway, and after more disassembly, Iv'e found all of the bearings are shot. I have been cleaning every orifis that I can find and so far no metal coming out. all the teeth from the gear were laying in the pan when I took it off. nothing in the oil pump either. got new bearings and crank turned. I had them chamfer the oil holes in the crank while they were at it. Just got it back today and it looks good. Now another Question, how do I find out exactely what year block I have? I'm tired of going to the parts store and asking for something, they ask what year, and the only thing I can tell them is that it's a early 80s motor. I did some research on the motor when I bought the car and came up with that. And it's out of a bus or a truck. Thanks again for all your help. it's much appreciated.
 
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