Knocking from top end?
Printed From: West Coast Fieros
Category: Technical Topics Forum
Forum Name: Technical Questions and Discussions
Forum Description: Got a technical question about your fiero? ask it here.
URL: http://www.westcoastfieros.com/forum/forum_posts.asp?TID=3010
Printed Date: 22 November 2024 at 3:06pm
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Topic: Knocking from top end?
Posted By: tweeder
Subject: Knocking from top end?
Date Posted: 05 August 2012 at 3:00pm
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I have a 90's 3800 swapped buy a previous owner. The bottom end
was supposedly done a few weeks ago. There is one or two knocks when it's fired up then as it gets warmer it will become more noticeable. That and when revved a few thousand rpms, but will go away if letting off the throttle. I took a stethoscope and it sounds like its coming from the front left( when standing at the back and looking forward). So I pulled off the valve cover and all looks fine no broken rocker or spring. Maybe a lifter? ------------- 86 GT Convertable 3800 |
Replies:
Posted By: karnak
Date Posted: 05 August 2012 at 4:22pm
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the noise is hard to hear from the keyboard. you describe the sound as a knock, not a tick. this give me the impression that a lifter may be a little optimistic. there are oil additives that might help that but if the bottom end was done, then why? was it a knock? if the crank was scored it would have been only a matter of time before that noise would return. have you done a listen from the bottom to hear what you can hear? Gary |
Posted By: tweeder
Date Posted: 05 August 2012 at 4:31pm
More of a knock? I'm assuming the bottom end con rods were done as they were no good. The mechanic that did the work told the previous owner that the top end will need work also, possible lifter. I couldn't get to the bottom as I was by myself and couldn't rev it. ------------- 86 GT Convertable 3800 |
karnak wrote:Posted By: Capt Fiero
Date Posted: 05 August 2012 at 4:47pm
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I had a collapsed piston in a 2.8 that sounded so much like a collapsed lifter that I tore the top end down replaced lifters, push rods and even rockers, and had no change. Out of frustration I decided to drive it till it blew. Then I would know for sure what the problem was. I went 2 years and 10 bottles of nitrous through it before I finally gave in pulled the motor and tore it down. Found out the #1 piston was most likely the cause of the original noise and the nitrous compounded the issue. I would check for any blow by and do a compression test on the motor. ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Posted By: tweeder
Date Posted: 05 August 2012 at 5:51pm
Will test compression when I get a chance. ------------- 86 GT Convertable 3800 |
Posted By: tweeder
Date Posted: 30 August 2012 at 8:42pm
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Pulled the pan and it's a connecting rod bearing. I will replace it and
hope it lasts another month and a half intill it gets parked and the 3800sc gets swapped in. ------------- 86 GT Convertable 3800 |
Posted By: tweeder
Date Posted: 01 September 2012 at 5:24pm
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Got'er in and alls quiet now. It was a spun bearing so we'll see how it
goes. ------------- 86 GT Convertable 3800 |
Posted By: karnak
Date Posted: 01 September 2012 at 7:32pm
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good news! i hope it lasts a long time.
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