Home » Public Forums » GMCnet » Front engine mount
| Front engine mount [message #350654] |
Fri, 13 December 2019 09:32  |
Tilerpep
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma: 7
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Senior Member |
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How high does the motor need to go to replace front engine mount?
Any existing write ups for that specifically?
Thanks
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
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| Re: Front engine mount [message #350655 is a reply to message #350654] |
Fri, 13 December 2019 09:53  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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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/
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| Re: [GMCnet] Front engine mount [message #350657 is a reply to message #350655] |
Fri, 13 December 2019 11:22 |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
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Senior Member |
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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 <
gmclist@list.gmcnet.org> wrote:
> 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
>
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| Re: Front engine mount [message #350658 is a reply to message #350654] |
Fri, 13 December 2019 12:00 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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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.
Tilerpep wrote on Fri, 13 December 2019 10:32How 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
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| Re: [GMCnet] Front engine mount [message #350659 is a reply to message #350658] |
Fri, 13 December 2019 12:33 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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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 <
gmclist@list.gmcnet.org> wrote:
> 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.
>
>
>
>
>
>
> Tilerpep wrote on Fri, 13 December 2019 10:32
>> 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
>
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| Re: Front engine mount [message #350660 is a reply to message #350654] |
Fri, 13 December 2019 12:41 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Tilerpep wrote on Fri, 13 December 2019 10:32How 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 - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Front engine mount [message #350661 is a reply to message #350659] |
Fri, 13 December 2019 12:56 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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https://www.gmcmi.com/wp-content/uploads/2014/05/X7525_75-76-maint-manual.pdf
James Hupy wrote on Fri, 13 December 2019 13:33R.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 <
gmclist@list.gmcnet.org> wrote:
> 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.
>
>
>
>
>
>
> Tilerpep wrote on Fri, 13 December 2019 10:32
>> 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
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| Re: Front engine mount [message #350662 is a reply to message #350654] |
Fri, 13 December 2019 13:08 |
Tilerpep
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma: 7
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Senior Member |
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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
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| Re: Front engine mount [message #350663 is a reply to message #350662] |
Fri, 13 December 2019 14:05 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Tilerpep wrote on Fri, 13 December 2019 14:08All 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 - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Front engine mount [message #350664 is a reply to message #350663] |
Fri, 13 December 2019 15:00 |
Tilerpep
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma: 7
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Senior Member |
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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
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