Unless the flexplate has a crack then the only way to find out where the knock is coming from would be to pull the oil pan. It was years ago I bought a 1996 Vortec 350 with what I was told was a spun bearing. I got it home, stipped it down and found the number 1 rod bearing spun and destroyed. It was obvious a piece of trash had found it`s way into the bearings and caused it to spin. The engine had around 50,000 miles on it. I also seen in another case where a engine spun a bearing yet still had excellant oil pressure.
97 Chevy Vortec 350 knock
Hi all! 
Here's my situation. I have a 97 Chevy K1500 4X4 with a Vortec 350 (VIN CODE R) in it which developed a knocking sound. The engine has 80K miles on it. It is a fairly loud knock at idle, but it's not hammering like a rod knock. Sounds like it's coming from the bottom end at or near the flywheel area. The knock gets lighter (A LOT LIGHTER) when I rev it while in park, and as soon as it comes back down to idle it is loud again. If I step on the brake and put it in drive to load the engine it is still loud, only slower in speed. And the whole time, no matter if it's in park or neutral, it's not a consistant sound, it varies so to speak. Almost like the knock skips a beat every so often while RPM remains consistant.
I have 50 PSI oil pressure cold, 40 PSI when hot. I have checked the crank pully bolts and they are tight. I pulled the serpentine belt and ran it with no real change in the noise. I have put my ear to a screwdriver at the oil pan and didn't hear anything unusual. I have the flexplate cover off and when laying under it with it running it sure sounds like it's coming from the flywheel area.
I took the torque converter bolts out of the flexplate, pushed the convertor back into the tranny and started the engine. Knock is still there, but lighter and a slightly different pitch to it.
So I'm wondering, since I have no apparent problems with oil pressure, no unusual noises coming from inside the oil pan, and the noise gets lighter under higher RPM with or without a load, where do I look next? I sure do look forward to your insight on this!
Thanks, Brian
Here's my situation. I have a 97 Chevy K1500 4X4 with a Vortec 350 (VIN CODE R) in it which developed a knocking sound. The engine has 80K miles on it. It is a fairly loud knock at idle, but it's not hammering like a rod knock. Sounds like it's coming from the bottom end at or near the flywheel area. The knock gets lighter (A LOT LIGHTER) when I rev it while in park, and as soon as it comes back down to idle it is loud again. If I step on the brake and put it in drive to load the engine it is still loud, only slower in speed. And the whole time, no matter if it's in park or neutral, it's not a consistant sound, it varies so to speak. Almost like the knock skips a beat every so often while RPM remains consistant.
I have 50 PSI oil pressure cold, 40 PSI when hot. I have checked the crank pully bolts and they are tight. I pulled the serpentine belt and ran it with no real change in the noise. I have put my ear to a screwdriver at the oil pan and didn't hear anything unusual. I have the flexplate cover off and when laying under it with it running it sure sounds like it's coming from the flywheel area.
I took the torque converter bolts out of the flexplate, pushed the convertor back into the tranny and started the engine. Knock is still there, but lighter and a slightly different pitch to it.
So I'm wondering, since I have no apparent problems with oil pressure, no unusual noises coming from inside the oil pan, and the noise gets lighter under higher RPM with or without a load, where do I look next? I sure do look forward to your insight on this!
Thanks, Brian
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This vortec motor "started to knock a little" too!
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Ouch...I don't think mine is knockin quite that bad!Plaintoast said:This vortec motor "started to knock a little" too!
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Problem found!
Well,
I pulled the motor, yanked the oil pan and found #8 rod bearing had spun. It ate in to the crank rod journal about an 1/8 inch. Also, #7 (on the same crank journal) was starting to go as well. This explains why the noise sounded like it was coming from the flywheel area.
Thanks for the info guys.
Well,
I pulled the motor, yanked the oil pan and found #8 rod bearing had spun.
It ate in to the crank rod journal about an 1/8 inch. Also, #7 (on the same crank journal) was starting to go as well. This explains why the noise sounded like it was coming from the flywheel area. Thanks for the info guys.
1 - 7 of 7 Posts
