West Coast Fieros Homepage
Forum Home Forum Home » Technical Topics Forum » Technical Questions and Discussions
  New Posts New Posts RSS Feed - Knocking from top end?
  FAQ FAQ  Forum Search   Register Register  Login Login

Knocking from top end?
 Post Reply Post Reply
Author
Message
  Topic Search Topic Search  Topic Options Topic Options
tweeder View Drop Down
Newbie
Newbie


Joined: 05 August 2012
Location: Canada
Status: Offline
Points: 27 		Post Options Post Options   Quote tweeder Quote  Post ReplyReply Direct Link To This Post Topic: Knocking from top end?
    Posted: 05 August 2012 at 3:00pm
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
Back to Top
karnak View Drop Down
Senior Member
Senior Member
Avatar

Joined: 28 August 2009
Location: Canada
Status: Offline
Points: 349 		Post Options Post Options   Quote karnak Quote  Post ReplyReply Direct Link To This Post Posted: 05 August 2012 at 4:22pm
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
Back to Top
tweeder View Drop Down
Newbie
Newbie


Joined: 05 August 2012
Location: Canada
Status: Offline
Points: 27 		Post Options Post Options   Quote tweeder Quote  Post ReplyReply Direct Link To This Post Posted: 05 August 2012 at 4:31pm
Originally posted by karnak karnak wrote:

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



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
Back to Top
Capt Fiero View Drop Down
Admin Group
Admin Group
Avatar
Founding Member

Joined: 12 February 2007
Location: Canada
Status: Offline
Points: 4039 		Post Options Post Options   Quote Capt Fiero Quote  Post ReplyReply Direct Link To This Post Posted: 05 August 2012 at 4:47pm
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.
Back to Top
tweeder View Drop Down
Newbie
Newbie


Joined: 05 August 2012
Location: Canada
Status: Offline
Points: 27 		Post Options Post Options   Quote tweeder Quote  Post ReplyReply Direct Link To This Post Posted: 05 August 2012 at 5:51pm
Originally posted by Capt Fiero Capt Fiero wrote:

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.


Will test compression when I get a chance.
86 GT Convertable 3800
Back to Top
tweeder View Drop Down
Newbie
Newbie


Joined: 05 August 2012
Location: Canada
Status: Offline
Points: 27 		Post Options Post Options   Quote tweeder Quote  Post ReplyReply Direct Link To This Post Posted: 30 August 2012 at 8:42pm
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
Back to Top
tweeder View Drop Down
Newbie
Newbie


Joined: 05 August 2012
Location: Canada
Status: Offline
Points: 27 		Post Options Post Options   Quote tweeder Quote  Post ReplyReply Direct Link To This Post Posted: 01 September 2012 at 5:24pm
Got'er in and alls quiet now. It was a spun bearing so we'll see how it
goes.
86 GT Convertable 3800
Back to Top
karnak View Drop Down
Senior Member
Senior Member
Avatar

Joined: 28 August 2009
Location: Canada
Status: Offline
Points: 349 		Post Options Post Options   Quote karnak Quote  Post ReplyReply Direct Link To This Post Posted: 01 September 2012 at 7:32pm

good news! i hope it lasts a long time.
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.01
Copyright ©2001-2018 Web Wiz Ltd.