LT1-LT4 Modifications 1993-97 Gen II Small Block V8

LT1 knock

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Old 09-11-2016, 05:36 PM
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Default LT1 knock

Hi guys, im new to this forum and new to using forums so please forgive me if i've posted this wrong or in the wrong place.

I need help fast. I just installed a new opti on my car and it ran great. Got excited and took it out on the road and drove the **** out of it. Ran a nice hard pull on a straightaway and bam... Loud rattling/knocking noise began right as i was about to shift at ~5750rpm. My guess is its a rod/main bearing but i want to be sure its not valve train before i try to sell it.

Any help is appreciated. Thanks
Old 09-12-2016, 10:08 AM
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A deep sounding knock can be associated with rotating assembly. Light metallic ticks are usually associated with valvetrain.
Old 09-12-2016, 12:57 PM
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Post video/audio to get a good opinion.
Old 09-12-2016, 02:49 PM
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are there any metal flakes now in the oil???....look at the dipstick

if this is a stock bottom end motor....shifting at "5750" is on the high side of RPM
Old 09-12-2016, 07:40 PM
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As far as i know bottom end is stock. Does have a mild cam though. It does sound like a heavy knock to me but i will post a video to see if you guys can identify it. I appreciate the replies
Old 09-12-2016, 08:19 PM
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here is a video. Also some smoke coming from passenger side...could be oil i dripped onro headers yesterday not sure.


Old 09-12-2016, 08:27 PM
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That almost sounds like maybe a push rod broke or rocker arm jumped off. Oil pressure looks good still. Pull that driver side valve cover and check your rockers. Check the other side too if that side is ok.
Old 09-12-2016, 10:03 PM
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I will definitely check tomorrow. I can also feel the knock in the clutch pedal if that tells you anything
Old 09-13-2016, 06:39 AM
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I think it sound more serious than valvetrain, but you should check it first. Flywheel interference can also make a nasty noise (if anything recent has been going on in that area).
Old 09-13-2016, 09:29 AM
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Sounds like the ring gear is hitting the dust cover, run over any speed bumps lately?
Old 09-13-2016, 09:52 AM
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Sounds bottom end'ish. Check the flywheel/flexplate as suggested.
Old 09-13-2016, 07:39 PM
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Didn't have time to pull valve covers today, but i did put an infrared temp gauge on the headers and the 2 rearmost ones (closest to firewall) were significantly colder than the rest. Also drained the oil and found small glitter sized metal shavings (some were slightly bigger) these were gold in color. I read somewhere that rob bearings, crank bearings, and cam bearings will all show gold flakes in oil. This leads me to beleieve that it could be a bearing but i need to be sure before i sell it lol.
Old 09-16-2016, 08:42 PM
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Pull the valve covers...
Old 09-17-2016, 11:29 AM
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Originally Posted by ******
are there any metal flakes now in the oil???....look at the dipstick
Originally Posted by Aussie420
. Also drained the oil and found small glitter sized metal shavings (some were slightly bigger) these were gold in color. .
....well there is your answer.
Old 09-18-2016, 02:19 PM
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Originally Posted by ******
....well there is your answer.
so you think its a bearing forsure? Thats my guess but i wanna be sure... Pulled valve covers today and all looks good. But the thing that is weird is that the back 2 headers are colder than the rest
Old 09-18-2016, 02:23 PM
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The knock rate says bottom end to me. Top end clicking/knocking will be half RPM speed.
Old 09-18-2016, 02:27 PM
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Originally Posted by Aussie420
But the thing that is weird is that the back 2 headers are colder than the rest
Those could be running rich (less air), due to their location to the TB at part throttle and at idle if the TB blades aren't set correctly. Could also be where the rods are knocking.
Old 09-18-2016, 04:11 PM
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Just pulled one if the plugs on the cold cylinders and the porcelain around the electrode was just flopping around... Compression is good on that cylinder



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