Front engine mount
- Thread starter tyler
- Start date
the motormount is held to the cross member by 2ea. studs with nuts. you go through the two holes at center cross member to access.
it is held to the front engine mount bracket by two nuts/bolts on outside edge. Those can be a pain to take off, but with the right wrench/socket it
can be done.
As far as how high you need to lift the engine, that could vary. theoretically after taking the bolts off the engine mount bracket, you take off 2
nuts off from the hole in the x-member, and it has to be lifted probably an inch. if you go to take the nuts off, and the studs spin out, then
it only needs to go up maybe 1/4" or less.
if I remember correctly, lifting is easy, and it is easy to lift the engine up to get that mount off, whatever height you need. It just takes some
rigging to get over the engine and get the right chain hoist in place.
I have a welded tool, that i can jack up from the lower end. it reached up and you jack up via the bolts on the oil pan. Lifting from top is much
better method.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
it is held to the front engine mount bracket by two nuts/bolts on outside edge. Those can be a pain to take off, but with the right wrench/socket it
can be done.
As far as how high you need to lift the engine, that could vary. theoretically after taking the bolts off the engine mount bracket, you take off 2
nuts off from the hole in the x-member, and it has to be lifted probably an inch. if you go to take the nuts off, and the studs spin out, then
it only needs to go up maybe 1/4" or less.
if I remember correctly, lifting is easy, and it is easy to lift the engine up to get that mount off, whatever height you need. It just takes some
rigging to get over the engine and get the right chain hoist in place.
I have a welded tool, that i can jack up from the lower end. it reached up and you jack up via the bolts on the oil pan. Lifting from top is much
better method.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
Word of warning here on lifting or raising the engine. NEVER NEVER try to
lift/raise the engine by using a floor jack on the bottom of the oil pan.
Even using a piece of wood between the pan and jack will not prevent the
damage. The clearance between the pan and the crank is close and you can
push the pan up so the crank hits the pan and that would be BAD! Lets just
say here that you would not be the first to do the wrong thing in
lift/raising the engine. You can make a simple lift support that uses the
block pan rails as the lift point. Look at the following pictures:
Read the captions under the pictures for relative information
http://www.gmcmhphotos.com/photos/general-pictures/p44885-engine-jacking-jig-for-lifting-motor.html
http://www.gmcmhphotos.com/photos/general-pictures/p44882-engine-jacking-jig-for-lifting-motor.html
http://www.gmcmhphotos.com/photos/general-pictures/p44883-engine-jacking-jig-for-lifting-motor.html
http://www.gmcmhphotos.com/photos/general-pictures/p44884-engine-jacking-jig-for-lifting-motor.html
J.R. Wright
GMC Great Laker
GMCGL Tech Editor
GMC Eastern States
GMCMHI
TZE Zone Restorations
78 Buskirk Custom 29.5' Stretch
75 Avion (Under going Frame up Restoration)
On Location in Tucson
On Fri, Dec 13, 2019 at 8:54 AM Jon Roche via Gmclist <
> the motormount is held to the cross member by 2ea. studs with nuts. you
> go through the two holes at center cross member to access.
>
> it is held to the front engine mount bracket by two nuts/bolts on outside
> edge. Those can be a pain to take off, but with the right wrench/socket it
> can be done.
>
> As far as how high you need to lift the engine, that could vary.
> theoretically after taking the bolts off the engine mount bracket, you
> take off 2
> nuts off from the hole in the x-member, and it has to be lifted probably
> an inch. if you go to take the nuts off, and the studs spin out, then
> it only needs to go up maybe 1/4" or less.
>
> if I remember correctly, lifting is easy, and it is easy to lift the
> engine up to get that mount off, whatever height you need. It just takes
> some
> rigging to get over the engine and get the right chain hoist in place.
>
> I have a welded tool, that i can jack up from the lower end. it reached
> up and you jack up via the bolts on the oil pan. Lifting from top is much
> better method.
>
>
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
lift/raise the engine by using a floor jack on the bottom of the oil pan.
Even using a piece of wood between the pan and jack will not prevent the
damage. The clearance between the pan and the crank is close and you can
push the pan up so the crank hits the pan and that would be BAD! Lets just
say here that you would not be the first to do the wrong thing in
lift/raising the engine. You can make a simple lift support that uses the
block pan rails as the lift point. Look at the following pictures:
Read the captions under the pictures for relative information
http://www.gmcmhphotos.com/photos/general-pictures/p44885-engine-jacking-jig-for-lifting-motor.html
http://www.gmcmhphotos.com/photos/general-pictures/p44882-engine-jacking-jig-for-lifting-motor.html
http://www.gmcmhphotos.com/photos/general-pictures/p44883-engine-jacking-jig-for-lifting-motor.html
http://www.gmcmhphotos.com/photos/general-pictures/p44884-engine-jacking-jig-for-lifting-motor.html
J.R. Wright
GMC Great Laker
GMCGL Tech Editor
GMC Eastern States
GMCMHI
TZE Zone Restorations
78 Buskirk Custom 29.5' Stretch
75 Avion (Under going Frame up Restoration)
On Location in Tucson
On Fri, Dec 13, 2019 at 8:54 AM Jon Roche via Gmclist <
> the motormount is held to the cross member by 2ea. studs with nuts. you
> go through the two holes at center cross member to access.
>
> it is held to the front engine mount bracket by two nuts/bolts on outside
> edge. Those can be a pain to take off, but with the right wrench/socket it
> can be done.
>
> As far as how high you need to lift the engine, that could vary.
> theoretically after taking the bolts off the engine mount bracket, you
> take off 2
> nuts off from the hole in the x-member, and it has to be lifted probably
> an inch. if you go to take the nuts off, and the studs spin out, then
> it only needs to go up maybe 1/4" or less.
>
> if I remember correctly, lifting is easy, and it is easy to lift the
> engine up to get that mount off, whatever height you need. It just takes
> some
> rigging to get over the engine and get the right chain hoist in place.
>
> I have a welded tool, that i can jack up from the lower end. it reached
> up and you jack up via the bolts on the oil pan. Lifting from top is much
> better method.
>
>
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
Sir, I have had no issues with using a good floor jack under the differential to raise the front of the engine enough to swap front engine mount.
> How high does the motor need to go to replace front engine mount?
>
> Any existing write ups for that specifically?
>
> Thanks
--
C. Boyd
76 Crestmont
East Tennessee
> How high does the motor need to go to replace front engine mount?
>
> Any existing write ups for that specifically?
>
> Thanks
--
C. Boyd
76 Crestmont
East Tennessee
R.T.S.M. (Read The Shop Manual) It gives very detailed instructions on how
to service the timing set in the vehicle. Good pictures of the lifting
device to raise the front of the engine to perform tasks like transmission
and final drive service, as well as timing chain sets, etc.
Oh, you say you don't have a shop manual? Gary Bovee has C.D.'a of his
"Idiots Guide to GMC" I think they are still available. More than you ever
wanted to know about em.
Jim Hupy
Salem, Oregon
On Fri, Dec 13, 2019, 10:13 AM Charles Boyd via Gmclist <
> Sir, I have had no issues with using a good floor jack under the
> differential to raise the front of the engine enough to swap front engine
> mount.
>
>
>
>
>
>
> > How high does the motor need to go to replace front engine mount?
> >
> > Any existing write ups for that specifically?
> >
> > Thanks
>
>
> --
> C. Boyd
> 76 Crestmont
> East Tennessee
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
to service the timing set in the vehicle. Good pictures of the lifting
device to raise the front of the engine to perform tasks like transmission
and final drive service, as well as timing chain sets, etc.
Oh, you say you don't have a shop manual? Gary Bovee has C.D.'a of his
"Idiots Guide to GMC" I think they are still available. More than you ever
wanted to know about em.
Jim Hupy
Salem, Oregon
On Fri, Dec 13, 2019, 10:13 AM Charles Boyd via Gmclist <
> Sir, I have had no issues with using a good floor jack under the
> differential to raise the front of the engine enough to swap front engine
> mount.
>
>
>
>
>
>
> > How high does the motor need to go to replace front engine mount?
> >
> > Any existing write ups for that specifically?
> >
> > Thanks
>
>
> --
> C. Boyd
> 76 Crestmont
> East Tennessee
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> How high does the motor need to go to replace front engine mount?
> Any existing write ups for that specifically?
> Thanks
Tyler,
I have more reason to look at the front mount than most. I have only changed with the engine out.
Other than support, you have answers there, There are two issues:
The mounting fasteners come in from both top and bottom.
The top two are really close to the oil pan (IIRC) and and the frame, a ratcheting box wrench is a great help or else it is 1/6 of 1/12 of a turn at a
time.
The studs on the bottom can be removed. I do not recall the thread size, but I think it is 3/8. To remove the studs (you will not be able to double
nut in the space), get a coupling nut. A coupling nut is just a double long nut. Get another screw to fit through it. Run that in to engage the
stud and then use the other screw to lock it. Then you should be able to remove the mount.
Watch the transmission, oil cooler and fuel line when you are lifting the engine.
This is what I did to get the lower fasteners out of the mount on the frame I removed. I did this before I discovered I needed to replace the frame
section. I also then identified that the mount should not be reused due to oil damage. So the new mount got a cover made out of aluminum flashing.
I hope it is a boring afternoon.
Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
> Any existing write ups for that specifically?
> Thanks
Tyler,
I have more reason to look at the front mount than most. I have only changed with the engine out.
Other than support, you have answers there, There are two issues:
The mounting fasteners come in from both top and bottom.
The top two are really close to the oil pan (IIRC) and and the frame, a ratcheting box wrench is a great help or else it is 1/6 of 1/12 of a turn at a
time.
The studs on the bottom can be removed. I do not recall the thread size, but I think it is 3/8. To remove the studs (you will not be able to double
nut in the space), get a coupling nut. A coupling nut is just a double long nut. Get another screw to fit through it. Run that in to engage the
stud and then use the other screw to lock it. Then you should be able to remove the mount.
Watch the transmission, oil cooler and fuel line when you are lifting the engine.
This is what I did to get the lower fasteners out of the mount on the frame I removed. I did this before I discovered I needed to replace the frame
section. I also then identified that the mount should not be reused due to oil damage. So the new mount got a cover made out of aluminum flashing.
I hope it is a boring afternoon.
Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
https://www.gmcmi.com/wp-content/uploads/2014/05/X7525_75-76-maint-manual.pdf
> R.T.S.M. (Read The Shop Manual) It gives very detailed instructions on how
> to service the timing set in the vehicle. Good pictures of the lifting
> device to raise the front of the engine to perform tasks like transmission
> and final drive service, as well as timing chain sets, etc.
> Oh, you say you don't have a shop manual? Gary Bovee has C.D.'a of his
> "Idiots Guide to GMC" I think they are still available. More than you ever
> wanted to know about em.
> Jim Hupy
> Salem, Oregon
>
> On Fri, Dec 13, 2019, 10:13 AM Charles Boyd via Gmclist <
>
> > Sir, I have had no issues with using a good floor jack under the
> > differential to raise the front of the engine enough to swap front engine
> > mount.
> >
> >
> >
> >
> >
> >
> >> How high does the motor need to go to replace front engine mount?
> >>
> >> Any existing write ups for that specifically?
> >>
> >> Thanks
> >
> >
> > --
> > C. Boyd
> > 76 Crestmont
> > East Tennessee
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
--
C. Boyd
76 Crestmont
East Tennessee
> R.T.S.M. (Read The Shop Manual) It gives very detailed instructions on how
> to service the timing set in the vehicle. Good pictures of the lifting
> device to raise the front of the engine to perform tasks like transmission
> and final drive service, as well as timing chain sets, etc.
> Oh, you say you don't have a shop manual? Gary Bovee has C.D.'a of his
> "Idiots Guide to GMC" I think they are still available. More than you ever
> wanted to know about em.
> Jim Hupy
> Salem, Oregon
>
> On Fri, Dec 13, 2019, 10:13 AM Charles Boyd via Gmclist <
>
> > Sir, I have had no issues with using a good floor jack under the
> > differential to raise the front of the engine enough to swap front engine
> > mount.
> >
> >
> >
> >
> >
> >
> >> How high does the motor need to go to replace front engine mount?
> >>
> >> Any existing write ups for that specifically?
> >>
> >> Thanks
> >
> >
> > --
> > C. Boyd
> > 76 Crestmont
> > East Tennessee
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
--
C. Boyd
76 Crestmont
East Tennessee
All good info thanks!
Chuck, you had your hands on this coach up at Bean Station one year working on the upper steering joint. Which, by the way, is doing fine!
We tried to diagnose the ongoing hot restart knock that year (which is not doing fine, getting slowly worse over the years), but I think I'll start a
new thread for that set of prognostication
--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
Chuck, you had your hands on this coach up at Bean Station one year working on the upper steering joint. Which, by the way, is doing fine!
We tried to diagnose the ongoing hot restart knock that year (which is not doing fine, getting slowly worse over the years), but I think I'll start a
new thread for that set of prognostication
--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
> All good info thanks!
>
> Chuck, you had your hands on this coach up at Bean Station one year working on the upper steering joint. Which, by the way, is doing fine!
>
> We tried to diagnose the ongoing hot restart knock that year (which is not doing fine, getting slowly worse over the years), but I think I'll
> start a new thread for that set of prognostication
Tyler,
I have had to track three hot restart knocks. All three were caused by fuel leakage. Only one was a normal carburetor, the others were TB and port
fuel. It does not take a great deal of fuel to make the knock. In one case, it did damage the engine.
Immediate restart was worst, but it mitigated with time. I suspect this is because the excess fuel drained past the rings.
We discovered this when hand turning the engine shortly after shutdown. It was not always the same cylinder in a specific engine and I wish I could
tell you more but the memory file has been damaged with age.
If a lubricating oil analysis show a lot of fuel dilution, you got it.
Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
>
> Chuck, you had your hands on this coach up at Bean Station one year working on the upper steering joint. Which, by the way, is doing fine!
>
> We tried to diagnose the ongoing hot restart knock that year (which is not doing fine, getting slowly worse over the years), but I think I'll
> start a new thread for that set of prognostication
Tyler,
I have had to track three hot restart knocks. All three were caused by fuel leakage. Only one was a normal carburetor, the others were TB and port
fuel. It does not take a great deal of fuel to make the knock. In one case, it did damage the engine.
Immediate restart was worst, but it mitigated with time. I suspect this is because the excess fuel drained past the rings.
We discovered this when hand turning the engine shortly after shutdown. It was not always the same cylinder in a specific engine and I wish I could
tell you more but the memory file has been damaged with age.
If a lubricating oil analysis show a lot of fuel dilution, you got it.
Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
Hmmm,
Matt my only other immediately available test/change would be to swap the carb off my 403 to the 455 with the knock. I presume it would run well
enough to at least tell if that is a cause?
And one thing I think would disqualify the fuel leak as cause is that under certain conditions I can hear it tocking away under what I would call a
loaded idle condition (in gear, sitting still, holding with gas on a bit of a hill type situation)?
--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
Matt my only other immediately available test/change would be to swap the carb off my 403 to the 455 with the knock. I presume it would run well
enough to at least tell if that is a cause?
And one thing I think would disqualify the fuel leak as cause is that under certain conditions I can hear it tocking away under what I would call a
loaded idle condition (in gear, sitting still, holding with gas on a bit of a hill type situation)?
--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
