1996 Collector Edition Corvette

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Basement Paul
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Re: 1996 Collector Edition Corvette

Post by Basement Paul »

If the chain is barely hitting when it's running, it may not hit at all when you're spinning it slowly. It definitely moves around in ways you won't be able to duplicate on a slow turn. I would still venture that the big chain is still rubbing and think the timing cover will show at least small marks if you take it off and look inside. Then again, I could be all wet, but that seems to be the biggest question mark.

-BP
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wxo
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Re: 1996 Collector Edition Corvette

Post by wxo »

I agree,BP. I'm pretty much resigned to taking everything apart again and digging down to the timing sprockets and chain. I'm just not real anxious to do it again.
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Basement Paul
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Re: 1996 Collector Edition Corvette

Post by Basement Paul »

Nobody would want to do that again. At least it will go faster this time knowing what you know.

-BP
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wxo
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Back at it again

Post by wxo »

I'm back at it again. Right now my objective is to get the oil pan off to clean out all the metal debris from whatever is causing it. I've been picking at it for the last couple of days and it's about ready to come down. If I have time tomorrow, I will get the engine hoist out of storage and lift the engine to remove the pan. One good thing about working under there this time is that everything is clean and dry. With the oil pan off, I can pull the balancer hub and this will allow the timing cover to be removed. I can't wait to take a peek inside.
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wxo
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Re: 1996 Collector Edition Corvette

Post by wxo »

Moving ahead, I decided to remove the balancer hub this afternoon when I realized that I had broken the puller that I used the last time I did this. So I had to engineer a puller from what I had available. I tried a one idea and spent a couple of hours on it before I decided that it wouldn't work. I scratched my head a bit more and came up with this.
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I used a few parts from the other puller I had bought to get the balancer off. It has a good design and worked great.
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Next I got the engine hoist out of storage and set it up to lift the engine for the removal of the oil pan. Once that's done it's time to unbolt the timing cover to see what's going on under there.
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Maybe Monday.
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wxo
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Good news, bad news

Post by wxo »

As promised, I was able to get the timing cover off this afternoon. I saw no evidence of rubbing or scraping or even steel shavings in the bottom of the cover. I guess you would call that the good news. When I removed the oil filter, these steel shavings were in the bottom of the catch container
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Remember that there was nothing like this in the filter when I cut it apart. Well, they had to come from somewhere. I just have to find the source.
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Basement Paul
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Re: 1996 Collector Edition Corvette

Post by Basement Paul »

It has to be from something you changed. Is there any signs of rubbing/grinding from the optispark? I know it spun free when it was out, but if it's a hair too long or big around somewhere, it may be rubbing when it's in the motor. Just guessing at stuff...

-BP
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wxo
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Re: 1996 Collector Edition Corvette

Post by wxo »

Thanks for offering your thoughts, BP. You are right. Logic would point to something I touched.

The Opti-Spark is bolted to the outside of the timing cover and is pinned to and driven by the cam sprocket through a hole in the timing cover. I didn't see any evidence of steel chip or shavings on the Opti-Spark shaft when I removed it. I would also expect to see these shavings on the very bottom lip of the timing cover if they were coming from anything inside the timing cover. There was just a very small amount of black, very fine residue on the bottom lip of the timing cover. There is no evidence of metal chips on or around the chain and sprockets or stuck to the block behind them.

Based on what I'm seeing, I'm not inclined to remove the chain and sprockets, but I might have to do it just to be thorough in this investigation. Maybe my second set of eyes (Maverick) can make it over here to have a look before I do anything else. He might notice something I missed.
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Maverick
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Re: 1996 Collector Edition Corvette

Post by Maverick »

Tomorrow afternoon?
Maverick
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GMJohnny
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Re: 1996 Collector Edition Corvette

Post by GMJohnny »

WXO,

Can you see the back of the timing chain? How do the gears look?

GM
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wxo
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Re: 1996 Collector Edition Corvette

Post by wxo »

GM, I can't see the back of the sprockets unless I remove them and it seems inevitable that I will be doing that.
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wxo
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May have found the problem

Post by wxo »

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Yesterday afternoon, a few minutes before Maverick was due to arrive, I was staring down at the timing set before me and just by chance I grabbed the oil pump drive gear shaft and wiggled it. When I did, I heard a scritching sound very similar to that which we heard when the engine was running and in the same area of the sound. Since the bearing is pressed into the block, I was surprised to feel some movement of the shaft. Remember that this was the shaft that went to the machine shop to have the bearing and the gear pressed off and the gear replaced with the one that matches the new timing set. When Maverick arrived, we pulled the water pump drive shaft from the block and checked out the bearing. Although it had some wiggle to it, It felt smooth and quiet. :shock: Also, there were NO steel chips anywhere to be seen. :?: So where did the steel chips come from if this was the source of the noise? Thinking about it, if the bearing was dropping the chips, they must have been dropping into the lifter galley because that's the only open side of the bearing. Were they washed by the flow of oil into the oil pan? I pulled the oil pump pickup and looked at the impellers and saw some evidence/scars of steel chips going through, although there were none in the filter element when I cut it apart. This bearing, I believe, is the 103K mile original. Thinking back, it was a foolish decision on my part to reuse it, although, at the time when I assessed it, I believe there was no play or noise coming from it and it was very smooth rolling. Perhaps it was damaged during the work at the machine shop.

At this point, I have ordered a replacement bearing from Amazon https://smile.amazon.com/gp/product/B00 ... UTF8&psc=1 and I will take the shaft assembly back to the machine shop to get it replaced. I'm not completely comfortable, yet, on how to explain the lack of steel chips in the area. Maverick suggested cutting the old bearing apart to assess the damage and to understand more about this puzzle. I plan to do that.
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wxo
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Re: May have found the problem

Post by wxo »

Now I'm convinced that the water pump driveshaft bearing was the source of the noise and the steel filings in the oil pan. After I removed the driveshaft from the block, I flushed the bearing with brake cleaner and some filings came out. Not very much, but they were visible. I had a new bearing pressed on yesterday so I cut open the old bearing and could see that the races were badly pitted. So that part of the case is closed.

So now that I'm thinking about starting reassembly, I began to wonder how this bearing is lubricated during operation. It sits high on the front wall of the block just under the front lip of the intake manifold. The water pump side of the bearing is covered by it's retention plate, but the other side is exposed to the interior of the lifter gallery. I see no obvious path for oil to get to it. I guess it could get misted with oil mist in the lifter gallery. I have done a lot of searching online, but found no mention of lubrication for this bearing. I wonder if I should fill it with grease like a wheel bearing. I plan to pose the question on a forum to see what I can find out.

The other issue is that of the filings in the oil pan and what, if anything, I should do to protect the engine. My main piece of evidence is that fact that there were no filings in the oil filter. I assume that is due to the fact that the engine was not run very long. My inclination is to just put everything back together, clean out the oil pan, install a new oil filter and move forward. There might be some residual filings in the lifter gallery that have not been flushed down the oil drain path, but I think a new oil filter should catch them. I also thought about pouring a quart of oil through the bearing hole in the block. Seems to me that it should help flush more of the debris down toward the oil pan. As always, your thoughts and ideas are welcome.
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MostMint
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Re: 1996 Collector Edition Corvette

Post by MostMint »

After a couple hundred miles I would swap the oil filter again- by then any loose shavings should be collected in the filter.
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
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wxo
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Re: 1996 Collector Edition Corvette

Post by wxo »

Yes. It's a good thing I have a bunch of filters in stock.
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