Home » Public Forums » GMCnet » Engine Noise
| Engine Noise [message #225107] |
Thu, 10 October 2013 18:03  |
Darryl
Messages: 144
Registered: December 2011
Location: Northern California
Karma: 0
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Senior Member |
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78 403 with headers. 62,000 miles. I've been chasing a noise in the engine for the last 2,500 miles or so without any success at identifying it.
It's more of a loud "tick" than an knock. I put a timing light on it and the noise is in sync with the light so it should be in the valve train. I put a stethoscope on it and it seems to be in the driver's side head but I can't really tie it down to a particular cylinder. Through the stethoscope it sounds like light metal-to-metal contact. Pulled the valve cover and ran it - all the rocker arms and push rods seem to be functioning properly. Pulled spark plug wires hoping it would go away without one cylinder firing but no help. Put a hose down by the exhaust gaskets hoping for an exhaust leak but I don't hear or feel anything. Someone suggested pulling the carburetor to check for cracks in the intake manifold but a cracked manifold should make the engine run poorly (it runs fine) and I can't see how it would cause the noise I'm hearing.
It's only noticeable at idle, louder when cold and goes away when I put a little load on the engine. I just did an 1,100 mile round trip to Coos Bay. The engine ran great and the noise isn't any worse now than when we left.
We've got a 2,500 mile trip planned for the end of the month which I'm thinking about canceling until I can get this figured out. Anyone have any ideas?
Darryl Meyers
1978 Eleganza II
El Dorado Hills, CA
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| Re: Engine Noise [message #225108 is a reply to message #225107] |
Thu, 10 October 2013 18:18  |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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Darryl,
My guess is that it's something worn in the valve train.
Rocker Arm, Fulcrum or lifter.
Maybe you could remove the left valve cover and check
the rocker arms for wear. You wouldn't have to get
too deep into the engine.
Regards,
Bill
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: Engine Noise [message #225110 is a reply to message #225107] |
Thu, 10 October 2013 18:25 |
Darryl
Messages: 144
Registered: December 2011
Location: Northern California
Karma: 0
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Senior Member |
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Thanks, Bill.
I had the valve cover off and everything looked good. Nothing loose or obviously worn. I put the stethoscope on the rocker arms and didn't hear anything unusual.
My first thought when this started was a bad lifter but this doesn't act like a lifter. It doesn't go away when warm but it is affected by vacuum pressure - It goes away when I put a little load on the engine.
Darryl Meyers
1978 Eleganza II
El Dorado Hills, CA
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| Re: [GMCnet] Engine Noise [message #225111 is a reply to message #225107] |
Thu, 10 October 2013 18:29 |
mtnman111
Messages: 20
Registered: August 2004
Karma: 0
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Junior Member |
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I had a similar noise in the valve train of a chev v8 265 cc after rebuild, the shop Forman said you can tear it down, but I doubt you will find the problem, I elected to drive it til I sold it 6 years later, never gave me any trouble, my advice, drive it.
Have a great day, larry c.
> On Oct 10, 2013, at 4:03 PM, Darryl Meyers <hospacctg@att.net> wrote:
>
>
>
> 78 403 with headers. 62,000 miles. I've been chasing a noise in the engine for the last 2,500 miles or so without any success at identifying it.
>
> It's more of a loud "tick" than an knock. I put a timing light on it and the noise is in sync with the light so it should be in the valve train. I put a stethoscope on it and it seems to be in the driver's side head but I can't really tie it down to a particular cylinder. Through the stethoscope it sounds like light metal-to-metal contact. Pulled the valve cover and ran it - all the rocker arms and push rods seem to be functioning properly. Pulled spark plug wires hoping it would go away without one cylinder firing but no help. Put a hose down by the exhaust gaskets hoping for an exhaust leak but I don't hear or feel anything. Someone suggested pulling the carburetor to check for cracks in the intake manifold but a cracked manifold should make the engine run poorly (it runs fine) and I can't see how it would cause the noise I'm hearing.
>
> It's only noticeable at idle, louder when cold and goes away when I put a little load on the engine. I just did an 1,100 mile round trip to Coos Bay. The engine ran great and the noise isn't any worse now than when we left.
>
> We've got a 2,500 mile trip planned for the end of the month which I'm thinking about canceling until I can get this figured out. Anyone have any ideas?
> --
> Darryl Meyers
>
> 1978 Eleganza II
>
> El Dorado Hills, CA
> _______________________________________________
> GMCnet mailing list
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L Conley 260 glacier
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| Re: Engine Noise [message #225116 is a reply to message #225107] |
Thu, 10 October 2013 19:18 |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
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Senior Member |
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Darryl,
Sounds like a lifter to me. You might try one of the "Mechanic in a can" products in the oil. Mystery Marvel Oil-Seafoam-Quart of ATF etc. etc. Run it for a few hundred miles see if it makes a difference.
Then change the oil and take your trip.
My 93 Jeep Cherokee has a noise like that. I've ignored it and it refuses to get worse or break.
Was nice meeting you at Coos Bay.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: [GMCnet] Engine Noise [message #225117 is a reply to message #225114] |
Thu, 10 October 2013 19:19 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Exhaust manifold or header gasket. Especially if it goes away when the engine warms up.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Engine Noise [message #225123 is a reply to message #225117] |
Thu, 10 October 2013 19:52 |
mrgmc3
Messages: 210
Registered: September 2013
Location: W Washington
Karma: 2
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Senior Member |
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Olds v8s have a unique arrangement of rocker arms and pivots. An aluminum pivot retains each pair of rockers. If the pivot and rocker interface wears significantly you can hear a valve train tick. It is easy to pull the pivots and inspect the interface surface. Replace both rockers and pivot if there is visible wear.
Chris Geils - Twin Cities / W Wa
1978 26' Kingsley w/ very few mods; PD9040, aux trans cooler, one repaint in stock colors, R134a, Al rad, Alcoas, 54k mi
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| Re: Engine Noise [message #225124 is a reply to message #225107] |
Thu, 10 October 2013 20:00 |
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batman
Messages: 100
Registered: January 2004
Location: Benbrook, TX
Karma: -3
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Senior Member |
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My 455 with headers made a loud "tick" noise since the first day I got it. Similar symptoms, noticeable at idle, not noticeable under load. Replaced exhaust gaskets thinking it was a leak, but that made no difference. When I switched to EFI and added a knock sensor, I would get constant false knocks from the "tick" noise at all speeds and loads.
I drove it for at least 70,000 miles with that ticking noise. Just recently had it rebuilt (for a different reason), and noticed some looseness on the passenger side valve train during dis-assembly. After the rebuild, the noises is gone 
| Darryl wrote on Thu, 10 October 2013 18:03 |
<snip>It's more of a loud "tick" than an knock. <snip>
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eugene
benbrook, tx
77 Eleganza II, Howell EFI + EBL
http://gmc.backyardwildlife.com
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| Re: Engine Noise [message #225129 is a reply to message #225107] |
Thu, 10 October 2013 20:06 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Except valve train noise shouldn't change with load. I'd look further at the exh manifold for crack.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Engine Noise [message #225169 is a reply to message #225151] |
Fri, 11 October 2013 00:00 |
mrgmc3
Messages: 210
Registered: September 2013
Location: W Washington
Karma: 2
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Senior Member |
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Stepping in here too...It is easy to check the rocker arms and rocker pivots. A little more involved to chech wrist pins!
Chris Geils - Twin Cities / W Wa
1978 26' Kingsley w/ very few mods; PD9040, aux trans cooler, one repaint in stock colors, R134a, Al rad, Alcoas, 54k mi
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| Re: [GMCnet] Engine Noise [message #225181 is a reply to message #225107] |
Fri, 11 October 2013 07:04 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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Try a piece of tubing long enough to reach from your ear to every joint on
the header to head, and header pipe to exhaust. Any leaks will be very
audible using this technique.
Steve F
On Thu, Oct 10, 2013 at 4:03 PM, Darryl Meyers <hospacctg@att.net> wrote:
>
>
> 78 403 with headers. 62,000 miles. I've been chasing a noise in the
> engine for the last 2,500 miles or so without any success at identifying it.
>
> It's more of a loud "tick" than an knock. I put a timing light on it and
> the noise is in sync with the light so it should be in the valve train. I
> put a stethoscope on it and it seems to be in the driver's side head but I
> can't really tie it down to a particular cylinder. Through the stethoscope
> it sounds like light metal-to-metal contact. Pulled the valve cover and
> ran it - all the rocker arms and push rods seem to be functioning properly.
> Pulled spark plug wires hoping it would go away without one cylinder
> firing but no help. Put a hose down by the exhaust gaskets hoping for an
> exhaust leak but I don't hear or feel anything. Someone suggested pulling
> the carburetor to check for cracks in the intake manifold but a cracked
> manifold should make the engine run poorly (it runs fine) and I can't see
> how it would cause the noise I'm hearing.
>
> It's only noticeable at idle, louder when cold and goes away when I put a
> little load on the engine. I just did an 1,100 mile round trip to Coos
> Bay. The engine ran great and the noise isn't any worse now than when we
> left.
>
> We've got a 2,500 mile trip planned for the end of the month which I'm
> thinking about canceling until I can get this figured out. Anyone have any
> ideas?
> --
> Darryl Meyers
>
> 1978 Eleganza II
>
> El Dorado Hills, CA
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Take care,
Steve
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| Re: [GMCnet] Engine Noise [message #225224 is a reply to message #225151] |
Fri, 11 October 2013 11:38 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I wore out a pair of 4 liter Jeep engines in Cherokees. It took just at 300K miles to accomplish. They were good motors - IF you supported the exhaust pipe properly so you didn't bust the exhaust manifold, and if you fed them front seals every 70 - 80 k miles. I shared one site with a bud with a 4runner for a company ride. I pulled him out with the Cherokees on a regular basis. We used to say, if you got to get there, there's Jeeps, and there's Everything Else.
--johnny
--------------------------------------------
On Fri, 10/11/13, Matt Colie <matt7323tze@gmail.com> wrote:
Subject: Re: [GMCnet] Engine Noise
To: gmclist@temp.gmcnet.org
Date: Friday, October 11, 2013, 2:37 AM
Darryl wrote on Thu, 10 October 2013 19:25
> Thanks, Bill.
>
> I had the valve cover off and everything looked
good. Nothing loose or obviously worn. I put the
stethoscope on the rocker arms and didn't hear anything
unusual.
>
> My first thought when this started was a bad lifter but
this doesn't act like a lifter. It doesn't go away
when warm but it is affected by vacuum pressure - It goes
away when I put a little load on the engine.
Darryl,
I almost hate to step in here. That description sounds
very much like a wrist pin that is loose. Notice
Batman mentioned a 4.0 Jeep? They were chronic for
just that, and they made that noise for about 150K before
the doors rusted off.
In the labs, we called it the diesel knock. It wasn't,
Kenosha just could make round holes for wrist pins.
Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumière (say show-me-air)
Now with 4 working Rear Brakes
SE Michigan - Twixt A2 and Detroit
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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