Timing Chain Change Out

[philip l. stewart]

Tony,
Would you please describe the symptoms your engine displayed that made you want
to change the timing chain? My engine (a 455) seems to run strong, but like
yours it has reached that 100,000 mile stage which others have indicated is the
point that most timing chains need replacing. I'm happy to perform recommended
preventative maintenance, but at the same time don't like to start 'fixing
things' that "ain't broke yet". BTW, Netters, has anyone ever broken a timing
chain or slipped a sprocket? How many miles on the engine when it happened?
Thanks, Tony, and anyone else who responds.
Phil Stewart
'76 Transmode, TN

> Alan,
>
> I am far from an expert, so maybe someone else has more info, but I just
> changed my timing chain and DID NOT have to remove oil pan. I went through
> the same confusion when I was planning this job. You will have to detach the
> front engine mount, but that is no big deal. I removed the fan shroud and
> fan so I had a lot of room to get in there. My chain had almost 100,000
> miles on it, and I almost was able to remove it without taking the gears
> off!
>
> A new one makes it feel like a new engine. Good luck.
>
> Tony B.
>
> ----- Original Message -----
> From: Alan Bredbury
> To: gmc mail list
> Sent: Monday, January 17, 2000 9:51 AM
>
> > You can call me a lurker, I seem to have trouble
> > getting the list to accept mail from me. I have a
> > question or two which I am sure someone out there can
> > help me with. First someone please tell me that the
> > GMC manual I have is wrong because if it is right I
> > need to remove the oil pan to get the front cover off
> > to do the timing chain and gears. Further the way it
> > is written it looks like you have to remove the final
> > drive to get the pan off. Yikes. I hope I am reading
> > this wrong. Second, Does anyone have a Napa part
> > number for the oil pressure shutdown switch for the
> > 6000 watt Onan? Thanks in advance. I am looking
> > forward to getting this work done before I go to FL in
> > Feburary starting tonight, lets see it's gonna be 15
> > degrees tonight and no garage, this ought to be fun.
> > Alan Bredbury in CT.
> > 1974 26' GMC owned for almost 2 years.
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Talk to your friends online with Yahoo! Messenger.
> > http://im.yahoo.com
> >

 

[antnip]

In all honesty, I really didn't notice a problem. I guess slow, long term
changes such as a chain wearing out are hard to notice. My prime motivation
was fear, as everyone kept telling me that I was long overdue for a change.
Once I made the change however, I noticed a big difference. It would seem
that all that slack allowed for a considerable variation in the timing. The
engine just seems to be better tuned, although the chain was the only
difference. It also seems much quieter that it did pre-change.

I, luckily, never experienced a broken timing chain on my GMC, however many
years back my friend and I tore down an engine from an old Chevette that had
lost it's timing chain, or it may have been a belt. Either way, it was not
pretty. Bend valves, scored cylinders, it was pretty bad. it is definitely
something to avoid.

The bottom line is that once I opened up, and saw all the slack in there, I
realized I should have done it earlier. Listen, I'm far from an expert on
these things, but if I were asked for my opinion, I'd say go ahead and
change it. It's time.

Tony B.

- ----- Original Message -----
From:
To:
Sent: Monday, January 17, 2000 5:41 PM
Subject: Re:GMC: Timing Chain Change Out

> Tony,
> Would you please describe the symptoms your engine displayed that made you
want
> to change the timing chain? My engine (a 455) seems to run strong, but
like
> yours it has reached that 100,000 mile stage which others have indicated
is the
> point that most timing chains need replacing. I'm happy to perform
recommended
> preventative maintenance, but at the same time don't like to start 'fixing
> things' that "ain't broke yet". BTW, Netters, has anyone ever broken a
timing
> chain or slipped a sprocket? How many miles on the engine when it
happened?
> Thanks, Tony, and anyone else who responds.
> Phil Stewart
> '76 Transmode, TN
>

>
> > Alan,
> >
> > I am far from an expert, so maybe someone else has more info, but I just
> > changed my timing chain and DID NOT have to remove oil pan. I went
through
> > the same confusion when I was planning this job. You will have to detach
the
> > front engine mount, but that is no big deal. I removed the fan shroud
and
> > fan so I had a lot of room to get in there. My chain had almost 100,000
> > miles on it, and I almost was able to remove it without taking the gears
> > off!
> >
> > A new one makes it feel like a new engine. Good luck.
> >
> > Tony B.
> >
> > ----- Original Message -----
> > From: Alan Bredbury
> > To: gmc mail list
> > Sent: Monday, January 17, 2000 9:51 AM
> >
> > > You can call me a lurker, I seem to have trouble
> > > getting the list to accept mail from me. I have a
> > > question or two which I am sure someone out there can
> > > help me with. First someone please tell me that the
> > > GMC manual I have is wrong because if it is right I
> > > need to remove the oil pan to get the front cover off
> > > to do the timing chain and gears. Further the way it
> > > is written it looks like you have to remove the final
> > > drive to get the pan off. Yikes. I hope I am reading
> > > this wrong. Second, Does anyone have a Napa part
> > > number for the oil pressure shutdown switch for the
> > > 6000 watt Onan? Thanks in advance. I am looking
> > > forward to getting this work done before I go to FL in
> > > Feburary starting tonight, lets see it's gonna be 15
> > > degrees tonight and no garage, this ought to be fun.
> > > Alan Bredbury in CT.
> > > 1974 26' GMC owned for almost 2 years.
> > >
> > > __________________________________________________
> > > Do You Yahoo!?
> > > Talk to your friends online with Yahoo! Messenger.
> > > http://im.yahoo.com
> > >
>
>

 

[heinz wittenbecher]

I changed mine at 100k and glad I did.
Timing chain slip was the (shop) reported demise of engine #1

In case you haven't looked at this already:
www.bytedesigns.com/gmc/timing.htm

Heinz
www.bytedesigns.com/gmc

- ----- Original Message -----
From:
To:
Sent: Tuesday, January 18, 2000 8:29 AM
Subject: Re: GMC: Timing Chain Change Out

> Tony,
> The timing chain on the GMC Motorhome is a well know wear item. There is
a procedure to check the time chain wear by measuring the distributor
movement. if someone has it please repost. The 100K point is a good time to
check and replace. Its not if, with the stock chain, but when it will break
or slip. It really is a high wear item and most have gone back the the
coyles double roller chain units. ($80) The Stock is a nylon gear which just
wears out.
>
> J.R. Wright
> GMC GreatLaker
> 77 Eleganza II
> Michigan
>

> > Tony,
> > Would you please describe the symptoms your engine displayed that made
you
> > want to change the timing chain? My engine (a 455) seems to run strong,
but
> > like yours it has reached that 100,000 mile stage which others have
> > indicated is the point that most timing chains need replacing. I'm happy
to
> > perform recommended preventative maintenance, but at the same time don't
> > like to start 'fixing things' that "ain't broke yet". BTW, Netters, has
> > anyone ever broken a timing chain or slipped a sprocket? How many miles
on
> > the engine when it happened? Thanks, Tony, and anyone else who responds.
> > Phil Stewart
> > '76 Transmode, TN
> >

> >
> > > Alan,
> > >
> > > I am far from an expert, so maybe someone else has more info, but I
just
> > > changed my timing chain and DID NOT have to remove oil pan. I went
> > through > the same confusion when I was planning this job. You will have
to
> > detach the > front engine mount, but that is no big deal. I removed the
fan
> > shroud and > fan so I had a lot of room to get in there. My chain had
> > almost 100,000 > miles on it, and I almost was able to remove it without
> > taking the gears > off!
> > >
> > > A new one makes it feel like a new engine. Good luck.
> > >
> > > Tony B.
> > >
> > > ----- Original Message -----
> > > From: Alan Bredbury
> > > To: gmc mail list
> > > Sent: Monday, January 17, 2000 9:51 AM
> > >
> > > > You can call me a lurker, I seem to have trouble
> > > > getting the list to accept mail from me. I have a
> > > > question or two which I am sure someone out there can
> > > > help me with. First someone please tell me that the
> > > > GMC manual I have is wrong because if it is right I
> > > > need to remove the oil pan to get the front cover off
> > > > to do the timing chain and gears. Further the way it
> > > > is written it looks like you have to remove the final
> > > > drive to get the pan off. Yikes. I hope I am reading
> > > > this wrong. Second, Does anyone have a Napa part
> > > > number for the oil pressure shutdown switch for the
> > > > 6000 watt Onan? Thanks in advance. I am looking
> > > > forward to getting this work done before I go to FL in
> > > > Feburary starting tonight, lets see it's gonna be 15
> > > > degrees tonight and no garage, this ought to be fun.
> > > > Alan Bredbury in CT.
> > > > 1974 26' GMC owned for almost 2 years.
> > > >
> > > > __________________________________________________
> > > > Do You Yahoo!?
> > > > Talk to your friends online with Yahoo! Messenger.
> > > > http://im.yahoo.com
> > > >
>
>
>
>

 

[ray]

Hi Tony, guess this is good timing (no pun intended). Yesterday I removed the
timing cover and discovered the same as you did, a very sloppy chain. my
questions then would be - did you need a puller for the engine sprocket and what
type did you use? I also don't know how to recognize the correct timing mark on
the crank gear.I see two dots and don't know which one is correct. I looked in
the GMC motorhome maintenance manul and it's still not clear to me. Appreciate
your help.

Ray and Elisa
1973 painted Desert
Corning CA

> In all honesty, I really didn't notice a problem. I guess slow, long term
> changes such as a chain wearing out are hard to notice. My prime motivation
> was fear, as everyone kept telling me that I was long overdue for a change.
> Once I made the change however, I noticed a big difference. It would seem
> that all that slack allowed for a considerable variation in the timing. The
> engine just seems to be better tuned, although the chain was the only
> difference. It also seems much quieter that it did pre-change.
>
> I, luckily, never experienced a broken timing chain on my GMC, however many
> years back my friend and I tore down an engine from an old Chevette that had
> lost it's timing chain, or it may have been a belt. Either way, it was not
> pretty. Bend valves, scored cylinders, it was pretty bad. it is definitely
> something to avoid.
>
> The bottom line is that once I opened up, and saw all the slack in there, I
> realized I should have done it earlier. Listen, I'm far from an expert on
> these things, but if I were asked for my opinion, I'd say go ahead and
> change it. It's time.
>
> Tony B.
>
> ----- Original Message -----
> From:
> To:
> Sent: Monday, January 17, 2000 5:41 PM
> Subject: Re:GMC: Timing Chain Change Out
>
> > Tony,
> > Would you please describe the symptoms your engine displayed that made you
> want
> > to change the timing chain? My engine (a 455) seems to run strong, but
> like
> > yours it has reached that 100,000 mile stage which others have indicated
> is the
> > point that most timing chains need replacing. I'm happy to perform
> recommended
> > preventative maintenance, but at the same time don't like to start 'fixing
> > things' that "ain't broke yet". BTW, Netters, has anyone ever broken a
> timing
> > chain or slipped a sprocket? How many miles on the engine when it
> happened?
> > Thanks, Tony, and anyone else who responds.
> > Phil Stewart
> > '76 Transmode, TN
> >

> >
> > > Alan,
> > >
> > > I am far from an expert, so maybe someone else has more info, but I just
> > > changed my timing chain and DID NOT have to remove oil pan. I went
> through
> > > the same confusion when I was planning this job. You will have to detach
> the
> > > front engine mount, but that is no big deal. I removed the fan shroud
> and
> > > fan so I had a lot of room to get in there. My chain had almost 100,000
> > > miles on it, and I almost was able to remove it without taking the gears
> > > off!
> > >
> > > A new one makes it feel like a new engine. Good luck.
> > >
> > > Tony B.
> > >
> > > ----- Original Message -----
> > > From: Alan Bredbury
> > > To: gmc mail list
> > > Sent: Monday, January 17, 2000 9:51 AM
> > >
> > > > You can call me a lurker, I seem to have trouble
> > > > getting the list to accept mail from me. I have a
> > > > question or two which I am sure someone out there can
> > > > help me with. First someone please tell me that the
> > > > GMC manual I have is wrong because if it is right I
> > > > need to remove the oil pan to get the front cover off
> > > > to do the timing chain and gears. Further the way it
> > > > is written it looks like you have to remove the final
> > > > drive to get the pan off. Yikes. I hope I am reading
> > > > this wrong. Second, Does anyone have a Napa part
> > > > number for the oil pressure shutdown switch for the
> > > > 6000 watt Onan? Thanks in advance. I am looking
> > > > forward to getting this work done before I go to FL in
> > > > Feburary starting tonight, lets see it's gonna be 15
> > > > degrees tonight and no garage, this ought to be fun.
> > > > Alan Bredbury in CT.
> > > > 1974 26' GMC owned for almost 2 years.
> > > >
> > > > __________________________________________________
> > > > Do You Yahoo!?
> > > > Talk to your friends online with Yahoo! Messenger.
> > > > http://im.yahoo.com
> > > >
> >
> >

 

[antnip]

It has been a little while, but I don't remember needing puller to get the
gears off. As far as timing marks, I'm embarrassed to say, I didn't pay much
attention to them. I made sure that nothing moved ( neither shaft was
turned, and put the new chain on the same way. Very unscientific, but it
worked nicely. My experience with timing belts/chains comes from working on
VW diesels, and the keep everything still method has worked on them. I'm
sure a real mechanic would cringe on hearing how I do it, but it has worked
so far. Good luck. Worrying about he job was actually a lot worse than doing
it.

Tony B.

- ----- Original Message -----
From: Ray Haywood
To:
Sent: Tuesday, January 18, 2000 12:45 PM
Subject: Re: GMC: Re:Timing Chain Change Out

> Hi Tony, guess this is good timing (no pun intended). Yesterday I removed
the
> timing cover and discovered the same as you did, a very sloppy chain. my
> questions then would be - did you need a puller for the engine sprocket
and what
> type did you use? I also don't know how to recognize the correct timing
mark on
> the crank gear.I see two dots and don't know which one is correct. I
looked in
> the GMC motorhome maintenance manul and it's still not clear to me.
Appreciate
> your help.
>
> Ray and Elisa
> 1973 painted Desert
> Corning CA

>
> > In all honesty, I really didn't notice a problem. I guess slow, long
term
> > changes such as a chain wearing out are hard to notice. My prime
motivation
> > was fear, as everyone kept telling me that I was long overdue for a
change.
> > Once I made the change however, I noticed a big difference. It would
seem
> > that all that slack allowed for a considerable variation in the timing.
The
> > engine just seems to be better tuned, although the chain was the only
> > difference. It also seems much quieter that it did pre-change.
> >
> > I, luckily, never experienced a broken timing chain on my GMC, however
many
> > years back my friend and I tore down an engine from an old Chevette that
had
> > lost it's timing chain, or it may have been a belt. Either way, it was
not
> > pretty. Bend valves, scored cylinders, it was pretty bad. it is
definitely
> > something to avoid.
> >
> > The bottom line is that once I opened up, and saw all the slack in
there, I
> > realized I should have done it earlier. Listen, I'm far from an expert
on
> > these things, but if I were asked for my opinion, I'd say go ahead and
> > change it. It's time.
> >
> > Tony B.
> >
> > ----- Original Message -----
> > From:
> > To:
> > Sent: Monday, January 17, 2000 5:41 PM
> > Subject: Re:GMC: Timing Chain Change Out
> >
> > > Tony,
> > > Would you please describe the symptoms your engine displayed that made
you
> > want
> > > to change the timing chain? My engine (a 455) seems to run strong,
but
> > like
> > > yours it has reached that 100,000 mile stage which others have
indicated
> > is the
> > > point that most timing chains need replacing. I'm happy to perform
> > recommended
> > > preventative maintenance, but at the same time don't like to start
'fixing
> > > things' that "ain't broke yet". BTW, Netters, has anyone ever broken
a
> > timing
> > > chain or slipped a sprocket? How many miles on the engine when it
> > happened?
> > > Thanks, Tony, and anyone else who responds.
> > > Phil Stewart
> > > '76 Transmode, TN
> > >

> > >
> > > > Alan,
> > > >
> > > > I am far from an expert, so maybe someone else has more info, but I
just
> > > > changed my timing chain and DID NOT have to remove oil pan. I went
> > through
> > > > the same confusion when I was planning this job. You will have to
detach
> > the
> > > > front engine mount, but that is no big deal. I removed the fan
shroud
> > and
> > > > fan so I had a lot of room to get in there. My chain had almost
100,000
> > > > miles on it, and I almost was able to remove it without taking the
gears
> > > > off!
> > > >
> > > > A new one makes it feel like a new engine. Good luck.
> > > >
> > > > Tony B.
> > > >
> > > > ----- Original Message -----
> > > > From: Alan Bredbury
> > > > To: gmc mail list
> > > > Sent: Monday, January 17, 2000 9:51 AM
> > > >
> > > > > You can call me a lurker, I seem to have trouble
> > > > > getting the list to accept mail from me. I have a
> > > > > question or two which I am sure someone out there can
> > > > > help me with. First someone please tell me that the
> > > > > GMC manual I have is wrong because if it is right I
> > > > > need to remove the oil pan to get the front cover off
> > > > > to do the timing chain and gears. Further the way it
> > > > > is written it looks like you have to remove the final
> > > > > drive to get the pan off. Yikes. I hope I am reading
> > > > > this wrong. Second, Does anyone have a Napa part
> > > > > number for the oil pressure shutdown switch for the
> > > > > 6000 watt Onan? Thanks in advance. I am looking
> > > > > forward to getting this work done before I go to FL in
> > > > > Feburary starting tonight, lets see it's gonna be 15
> > > > > degrees tonight and no garage, this ought to be fun.
> > > > > Alan Bredbury in CT.
> > > > > 1974 26' GMC owned for almost 2 years.
> > > > >
> > > > > __________________________________________________
> > > > > Do You Yahoo!?
> > > > > Talk to your friends online with Yahoo! Messenger.
> > > > > http://im.yahoo.com
> > > > >
> > >
> > >
>
>

 

[jim white]

Tony
if you remove the mechanical fuel pump you can see and feel the timing
chain....should give you a good idea of wear...
jim white
78 EII

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailtowner-gmcmotorhome]On Behalf Of powerjon
> Sent: Tuesday, January 18, 2000 10:29 AM
> To: gmcmotorhome
> Subject: Re: GMC: Timing Chain Change Out
>
>
> Tony,
> The timing chain on the GMC Motorhome is a well know wear item.
> There is a procedure to check the time chain wear by measuring
> the distributor movement. if someone has it please repost. The
> 100K point is a good time to check and replace. Its not if, with
> the stock chain, but when it will break or slip. It really is a
> high wear item and most have gone back the the coyles double
> roller chain units. ($80) The Stock is a nylon gear which just wears out.
>
> J.R. Wright
> GMC GreatLaker
> 77 Eleganza II
> Michigan
>

> > Tony,
> > Would you please describe the symptoms your engine displayed
> that made you
> > want to change the timing chain? My engine (a 455) seems to run
> strong, but
> > like yours it has reached that 100,000 mile stage which others have
> > indicated is the point that most timing chains need replacing.
> I'm happy to
> > perform recommended preventative maintenance, but at the same time don't
> > like to start 'fixing things' that "ain't broke yet". BTW, Netters, has
> > anyone ever broken a timing chain or slipped a sprocket? How
> many miles on
> > the engine when it happened? Thanks, Tony, and anyone else who responds.
> > Phil Stewart
> > '76 Transmode, TN
> >

> >
> > > Alan,
> > >
> > > I am far from an expert, so maybe someone else has more info,
> but I just
> > > changed my timing chain and DID NOT have to remove oil pan. I went
> > through > the same confusion when I was planning this job. You
> will have to
> > detach the > front engine mount, but that is no big deal. I
> removed the fan
> > shroud and > fan so I had a lot of room to get in there. My chain had
> > almost 100,000 > miles on it, and I almost was able to remove it without
> > taking the gears > off!
> > >
> > > A new one makes it feel like a new engine. Good luck.
> > >
> > > Tony B.
> > >
> > > ----- Original Message -----
> > > From: Alan Bredbury
> > > To: gmc mail list
> > > Sent: Monday, January 17, 2000 9:51 AM
> > >
> > > > You can call me a lurker, I seem to have trouble
> > > > getting the list to accept mail from me. I have a
> > > > question or two which I am sure someone out there can
> > > > help me with. First someone please tell me that the
> > > > GMC manual I have is wrong because if it is right I
> > > > need to remove the oil pan to get the front cover off
> > > > to do the timing chain and gears. Further the way it
> > > > is written it looks like you have to remove the final
> > > > drive to get the pan off. Yikes. I hope I am reading
> > > > this wrong. Second, Does anyone have a Napa part
> > > > number for the oil pressure shutdown switch for the
> > > > 6000 watt Onan? Thanks in advance. I am looking
> > > > forward to getting this work done before I go to FL in
> > > > Feburary starting tonight, lets see it's gonna be 15
> > > > degrees tonight and no garage, this ought to be fun.
> > > > Alan Bredbury in CT.
> > > > 1974 26' GMC owned for almost 2 years.
> > > >
> > > > __________________________________________________
> > > > Do You Yahoo!?
> > > > Talk to your friends online with Yahoo! Messenger.
> > > > http://im.yahoo.com
> > > >
>
>
>

 

[ray]

It's a good thought . Thanks

> In a message dated 01/18/2000 11:45:54 AM Central Standard Time,

>
> > also don't know how to recognize the correct timing mark on
> > the crank gear.I see two dots and don't know which one is correct. I
> looked
> > in
> > the GMC motorhome maintenance manul and it's still not clear to me.
> > Appreciate
> > your help.
> >
> Ray
>
> I would like to add something at this point. While you are in there working
> on the chain and everything take the time to degree everything in. Mine
> was a mess. First of all if you set the timing at 8d BTDC it was actually
> firing at TDC. The old cam was advanced 6d from where it should have
> been. Now this is a rebuilt engine so I dont know if it was just miss
> matched parts or what. I will bet it runs a lot better afterwards. This
> may also explain why I was not getting any pinging with the 23d
> vacuum advance. Oh well just a thought.
>
> Take Care
> Arch