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Old 11-06-2007, 04:04 AM   #1
Sportstr1200
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Unhappy I keep spinning #1 rod bearing on a 5.7 Vortec. Help me please!!

Hi guys. This is Mike and I'm new here. I hope I'm doing this right.

I have a 1998 2500 Silverado with a 5.7 Vortec engine. I bought it with 181,000 miles on it and it ran great. I only drove it for about 1k miles when I noticed it was knocking a bit during deceleration. A mechanic friend of mine told me it was a rod bearing because the noise goes away under any type of load. Since I consider myself a "do-it-yourself" kinda guy, I dropped the oil pan to see what I could see. I grabbed onto each rod and tried to move it around. the first rod from the front of the crank had a LOT of slop but the rest just had a very little. I bought a new set of standard size bearings at Auto Zone and replaced them all. I then grabbed all the rods and they all felt tight except the first one again. It still had a lot of slop. My friend suggested I get a .020 over bearing so I put it in and now no slop in that rod. I also installed a high volume oil pump while I was there and then I put it all back together. I oiled it up with Valvoline high mileage syn blend 10-30 and 1 quart of Lucus oil treatment. I fired it up and It ran like a dream without any noise at all for 50 miles, then knock, knock , knock.
Being the kind of guy that I am, I got mad and took it all apart again to find that the bearing had spun on that first rod. I didnt seek any advice and just put another bearing in it thinking that maybe I didnt lube the bearing enough when I installed it . You can probably guess what happened next. It ran great for about 30 miles and now it's knocking again. I'm sure I must have done something wrong but I'm not smart enough to know what. The crank has some grooves in it but it feels smooth to the touch. The bearing isnt chewed up or anything, it's just all black from the heat. The oil pressure is about 70lbs at idle when I first start the truck and 40lbs at idle when it's all warmed up. There is no knock at idle but when I rev it up it knocks on deceleration.

What did I do wrong???

I would appriciate any constructive advise on how I can fix the problem without pulling the engine out. I cant afford a new engine so I'm hoping I can fix this one.

Thank you for reading my post and I look forward to any replies.

Mike
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Old 11-06-2007, 04:38 AM   #2
dodger65
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what you did wrong: you put a undersize bearing in without knowing what the unintentional undersizing of the crank was...

the crankshaft is going to have to be removed, resized and/or replaced.

and you're going to either have to pull the engine or trans to do it...

your choice depending on how much you like to work on your back. i'd pull the engine...

buy a shop manual, too...
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Old 11-06-2007, 04:20 PM   #3
67Coronet383
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My god. This one is up there.
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Old 11-08-2007, 04:51 PM   #4
yota
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Quote:
Originally Posted by dodger65
what you did wrong: you put a under size bearing in without knowing what the unintentional undersizing of the crank was...

the crankshaft is going to have to be removed, resized and/or replaced.

and you're going to either have to pull the engine or trans to do it...

your choice depending on how much you like to work on your back. i'd pull the engine...

buy a shop manual, too...
I agree the only other thing you might do because you like taking the pan off is to use some crush gauge.Maybe its 30 over.PS this is a uneducated answer
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