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| [GMCnet] timing chain tension? [message #211699] |
Thu, 20 June 2013 14:02  |
KB
Messages: 1262
Registered: September 2009
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So how tight is tight on the timing chain? While trying
to figure out "the noise" I've been looking carefully
at the engine. Seems (to my completely ignorant self)
that there's more slop in distributor vs piston movement
than would be ideal. I'd also noticed some time ago that the
timing mark seemed to drift a bit when I was trying to set it
to install efi, but again, I've never done any of this stuff before.
I pulled the plate where the mechanical fuel pump used to be
and reached in and down as far as possible. I could pull the
chain outward maybe 1/8" or so, just below the upper gear wheel.
Is that normal, bad, ??
The engine was replaced about 12k miles ago per receipts,
supposedly by a reputable shop. The prior engine had a Cloyes
true roller chain installed by Tom Hampton not long before the swap,
but that doesn't appear have made it onto this engine :-(
Still no clue what "the noise" is, though I've found other
problems to worry about.
thanks
Karen
1973 23'
1975 26'
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1975 26'
San Jose, CA
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| Re: [GMCnet] timing chain tension? [message #211701 is a reply to message #211699] |
Thu, 20 June 2013 14:18  |
James Hupy
Messages: 6806
Registered: May 2010
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Karen, at the point where you can access the timing chain through the fuel
pump port, if you have more than 1/4" slack on that side, you will have
some retarded valve timing. I have seen as much as a 1/2 " slack there and
the engine would not pull below 1800 or so. I do not think that the slack
you presently see would cause the noise you hear unless the fastener that
secures the cam sprocket is loose. You might check the big bolt that
secures the crankshaft vibration compensator. I have seen them come loose,
and check the outside ring on the compensator(the one with the TDC
indicator line) If some idiot put that piece in the solvent tank it will
soften the molded rubber core. They will knock like you are describing.
Rule out everything that it isn't, what is left is your problem. I would
take off all your belts and run the engine a few seconds to rule out all
your accessories as well.
Jim Hupy
Salem, Or
78 Gmc Royale 403
On Jun 20, 2013 12:02 PM, "KB" <kab7@sonic.net> wrote:
> So how tight is tight on the timing chain? While trying
> to figure out "the noise" I've been looking carefully
> at the engine. Seems (to my completely ignorant self)
> that there's more slop in distributor vs piston movement
> than would be ideal. I'd also noticed some time ago that the
> timing mark seemed to drift a bit when I was trying to set it
> to install efi, but again, I've never done any of this stuff before.
>
> I pulled the plate where the mechanical fuel pump used to be
> and reached in and down as far as possible. I could pull the
> chain outward maybe 1/8" or so, just below the upper gear wheel.
> Is that normal, bad, ??
>
> The engine was replaced about 12k miles ago per receipts,
> supposedly by a reputable shop. The prior engine had a Cloyes
> true roller chain installed by Tom Hampton not long before the swap,
> but that doesn't appear have made it onto this engine :-(
>
> Still no clue what "the noise" is, though I've found other
> problems to worry about.
>
> thanks
> Karen
> 1973 23'
> 1975 26'
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] timing chain tension? [message #211702 is a reply to message #211699] |
Thu, 20 June 2013 14:26 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Karen, while you have the fuel pump off put a breaker bar on the balancer nut and see how much rotation you have back and forth. Check tension on loose side of rotation. A bad balancer will also cause a "knock". Usually a bad balancer will show when trying to time it with a light and the marks just won`t act right.
| KB wrote on Thu, 20 June 2013 15:02 |
So how tight is tight on the timing chain? While trying
to figure out "the noise" I've been looking carefully
at the engine. Seems (to my completely ignorant self)
that there's more slop in distributor vs piston movement
than would be ideal. I'd also noticed some time ago that the
timing mark seemed to drift a bit when I was trying to set it
to install efi, but again, I've never done any of this stuff before.
I pulled the plate where the mechanical fuel pump used to be
and reached in and down as far as possible. I could pull the
chain outward maybe 1/8" or so, just below the upper gear wheel.
Is that normal, bad, ??
The engine was replaced about 12k miles ago per receipts,
supposedly by a reputable shop. The prior engine had a Cloyes
true roller chain installed by Tom Hampton not long before the swap,
but that doesn't appear have made it onto this engine 
Still no clue what "the noise" is, though I've found other
problems to worry about.
thanks
Karen
1973 23'
1975 26'
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C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] timing chain tension? [message #211703 is a reply to message #211699] |
Thu, 20 June 2013 14:45 |
kelvin
Messages: 608
Registered: February 2004
Location: Eugene, OR
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A picture with 20-30 words?
75,000 miles on the left chain...
http://www.gmcmhphotos.com/photos/455-r-amp-r-engine-work/p10855.html
On 6/20/2013 12:02 PM, KB wrote:
> So how tight is tight on the timing chain? While trying
> to figure out "the noise" I've been looking carefully
> at the engine. Seems (to my completely ignorant self)
> that there's more slop in distributor vs piston movement
> than would be ideal. I'd also noticed some time ago that the
> timing mark seemed to drift a bit when I was trying to set it
> to install efi, but again, I've never done any of this stuff before.
>
> I pulled the plate where the mechanical fuel pump used to be
> and reached in and down as far as possible. I could pull the
> chain outward maybe 1/8" or so, just below the upper gear wheel.
> Is that normal, bad, ??
>
> The engine was replaced about 12k miles ago per receipts,
> supposedly by a reputable shop. The prior engine had a Cloyes
> true roller chain installed by Tom Hampton not long before the swap,
> but that doesn't appear have made it onto this engine :-(
>
> Still no clue what "the noise" is, though I've found other
> problems to worry about.
>
> thanks
> Karen
> 1973 23'
> 1975 26'
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] timing chain tension? [message #211727 is a reply to message #211699] |
Thu, 20 June 2013 18:34 |
KB
Messages: 1262
Registered: September 2009
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Thanks guys. If I unload the chain by turning the crank back
the other way, I get a LOT more slop in the chain. Turning it
back and forth and measuring, I'll guesstimate about 5-6 degrees
before it runs into resistance.
How can I tell if the balancer is bad? I can't see anything
obviously wrong.
I just disconnected the a/c belt (since that's the side the
sound seems to be coming from) and it seems a lot quieter,
at least to the extent I can tell by revving it in the driveway.
It's such an intermittent problem though, we won't know for sure
until we have a chance to get it out on the road.
Could an a/c compressor make a rattle/knock that only happens
at light throttle or when revving the engine??
Seems a stretch, but I wouldn't know.
thanks
Karen
1973 23'
1975 26'
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1975 26'
San Jose, CA
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| Re: [GMCnet] timing chain tension? [message #211734 is a reply to message #211727] |
Thu, 20 June 2013 19:35 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Karen, I would think 5-6* would be tolerable.
The only way I know of checking the balancer other than visual inspection is to replace with a known good one.
Yes the ac compressor has been known to hit the coach and any accessory that has lost a bolt or has a broke bracket can knock.
Might try taking the other 2 belts off and see if it makes any more difference. You will be running without a water pump so just a few seconds. Might leave the ps belt on if you need to run longer.
Thing that bothers me is the metal in the oil. If taking the belts off helps a lot, maybe the front main bearing is worn. Taking the belts off releaves the upward force they put on the crank and allows it to relax and not be pulled out of balance if the main is worn. Kinda usually rod bearing or wrist pin knock is consistant but a main bg knock is not. Rods wear the upper bearing shell and mains wear the lower.
| KB wrote on Thu, 20 June 2013 19:34 |
Thanks guys. If I unload the chain by turning the crank back
the other way, I get a LOT more slop in the chain. Turning it
back and forth and measuring, I'll guesstimate about 5-6 degrees
before it runs into resistance.
How can I tell if the balancer is bad? I can't see anything
obviously wrong.
I just disconnected the a/c belt (since that's the side the
sound seems to be coming from) and it seems a lot quieter,
at least to the extent I can tell by revving it in the driveway.
It's such an intermittent problem though, we won't know for sure
until we have a chance to get it out on the road.
Could an a/c compressor make a rattle/knock that only happens
at light throttle or when revving the engine??
Seems a stretch, but I wouldn't know.
thanks
Karen
1973 23'
1975 26'
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C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] timing chain tension? [message #211739 is a reply to message #211699] |
Thu, 20 June 2013 20:19 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I wouldn't go too much by the distributor as those spiral gear have some lash. Jim's balancer tip is a good one as that is a fooler. I'm assuming a timing chain and gear can be done in coach. Cheap fix if that is it and if you need a motor there is your first set of new parts. Did Olds use the nylon gear? Good to get rid of it if so.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] timing chain tension? [message #211747 is a reply to message #211699] |
Thu, 20 June 2013 22:55 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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maybe this will help
http://gmcmotorhome.info/engine.html#chain
gene
On Thu, Jun 20, 2013 at 12:02 PM, KB <kab7@sonic.net> wrote:
> So how tight is tight on the timing chain? While trying
> to figure out "the noise" I've been looking carefully
> at the engine. Seems (to my completely ignorant self)
> that there's more slop in distributor vs piston movement
> than would be ideal. I'd also noticed some time ago that the
> timing mark seemed to drift a bit when I was trying to set it
> to install efi, but again, I've never done any of this stuff before.
>
> I pulled the plate where the mechanical fuel pump used to be
> and reached in and down as far as possible. I could pull the
> chain outward maybe 1/8" or so, just below the upper gear wheel.
> Is that normal, bad, ??
>
> The engine was replaced about 12k miles ago per receipts,
> supposedly by a reputable shop. The prior engine had a Cloyes
> true roller chain installed by Tom Hampton not long before the swap,
> but that doesn't appear have made it onto this engine :-(
>
> Still no clue what "the noise" is, though I've found other
> problems to worry about.
>
> thanks
> Karen
> 1973 23'
> 1975 26'
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] timing chain tension? [message #211781 is a reply to message #211727] |
Fri, 21 June 2013 09:24 |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
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Karen,
I screwed up when I rotated the crank to get the slop on the fuel pump side. It was taught.
The next year I was down at the COOP and had pulled the oil pan. I said to Jim's mechanic Jason, "I know the chain is OK cause I
checked it last year but since I can get to it easily I'll check it again." With the pan off you can stick your fingers up on both
sides of the chain. When I did I felt a LOT of slack on BOTH sides! We wound up R&Ring the single stock chain with a double row
Cloyes that JimB had in stock.
Regards,
Rob M.
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of KB
Sent: Thursday, June 20, 2013 6:34 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] timing chain tension?
Thanks guys. If I unload the chain by turning the crank back
the other way, I get a LOT more slop in the chain. Turning it
back and forth and measuring, I'll guesstimate about 5-6 degrees
before it runs into resistance.
How can I tell if the balancer is bad? I can't see anything
obviously wrong.
I just disconnected the a/c belt (since that's the side the
sound seems to be coming from) and it seems a lot quieter,
at least to the extent I can tell by revving it in the driveway.
It's such an intermittent problem though, we won't know for sure
until we have a chance to get it out on the road.
Could an a/c compressor make a rattle/knock that only happens
at light throttle or when revving the engine??
Seems a stretch, but I wouldn't know.
thanks
Karen
1973 23'
1975 26'
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] timing chain tension? [message #211814 is a reply to message #211699] |
Fri, 21 June 2013 12:44 |
KB
Messages: 1262
Registered: September 2009
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> You say this motor was 'replaced' 12,000 miles ago. Was it rebuilt? That's a short time for a timing chain to loosen up, I think. Could you have lost a gear causing the metal in your oil?
I assume it was a rebuilt engine, but the receipt just says "engine"
(and then lists a lot of other parts, gaskets, etc, needed to get the
engine installed). Ie, the shop that did the install just got the
engine from a rebuilder.
I was hoping maybe the shavings were left over from the oil cooler
since the prior engine had a major failure (though this is a few oil
changes later). No such luck though -- they supposedly replaced the
radiator at the same time.
I'll check the gears more carefully with the bore scope (handy tool that,
even a cheap one)
thanks
Karen
1973 23'
1975 26'
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1975 26'
San Jose, CA
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| Re: [GMCnet] timing chain tension? [message #211844 is a reply to message #211814] |
Fri, 21 June 2013 19:28 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Karen,
If the shop got the engine from a "run of the mill" rebuilder I doubt that there is a Cloyes double roller chain in it. It's
probably a "run of the mill" chain.
Regards,
Rob M.
-----Original Message-----
From: KB
> You say this motor was 'replaced' 12,000 miles ago. Was it rebuilt? That's a short time for a timing chain to loosen up, I think.
Could you have lost a gear causing the metal in your oil?
I assume it was a rebuilt engine, but the receipt just says "engine"
(and then lists a lot of other parts, gaskets, etc, needed to get the
engine installed). Ie, the shop that did the install just got the
engine from a rebuilder.
I was hoping maybe the shavings were left over from the oil cooler
since the prior engine had a major failure (though this is a few oil
changes later). No such luck though -- they supposedly replaced the
radiator at the same time.
I'll check the gears more carefully with the bore scope (handy tool that,
even a cheap one)
thanks
Karen
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] timing chain tension? [message #211855 is a reply to message #211727] |
Fri, 21 June 2013 22:19 |
Dennis S
Messages: 3046
Registered: November 2005
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| KB wrote on Thu, 20 June 2013 18:34 |
snip snip..
Could an a/c compressor make a rattle/knock that only happens
at light throttle or when revving the engine??
Seems a stretch, but I wouldn't know.
thanks
Karen
1973 23'
1975 26'
|
Karen,
You might try rotating the ac compressor now that you have the belt off. My experience with the ac is limited -- but I have seen failing compressor that made a slight knock or growl at low rpm -- whether it was the clutch or the compressor.
Dennis
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] timing chain tension? [message #211887 is a reply to message #211699] |
Sat, 22 June 2013 15:03 |
KB
Messages: 1262
Registered: September 2009
Karma: 0
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Senior Member |
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> If the shop got the engine from a "run of the mill" rebuilder I doubt that there is a Cloyes double roller chain in it. It's
> probably a "run of the mill" chain.
Yup, which is a shame because the prior engine DID have a cloyes roller chain
(per receipts). The one that's in there now is the plain cheap-o variety. :-(
Karen
1973 23'
1975 26'
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Karen
1975 26'
San Jose, CA
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