Frist trip/cooling tips

D

dave1

New member
Jul 23, 1998
460
0
0
>Just back from our short trip to Ca. from AZ. ... any tips to
>improve engine& tranny temps? Thanks and keep on GMCing.

I have been very aggressive at keeping my operating temps low. I like to
run my engines at 160 degrees and do whatever it takes to keep them there.
You may or may not want to be that aggressive but here is how I did it...

1) Install Robertshaw 160 degree thermostat (P/N 330-160 I think).

2) Install a heavy duty fan clutch. If it still allows the operating temp
to go over 160 degrees (mine did) then adjust the thermostat on the fan
clutch. This can be done by making a new slot in the bracket that holds the
outer end of the thermostat coil and moving the fixed end of the coil to
the new slot. I adjusted mine so it starts to engage at 75 degrees outside
temp (with the dash A/C turned on).

3) Check your timing and the timing advance curves. If you still have the
older points style ignition, be sure its tuned up properly. The ignition on
our 73's all used the breaker point style distributor. If your engine has
electronic ignition then it has been upgraded and there is a good chance
that you may not have the correct distributor.

I learned that the timing curves are very critical. For years I had to use
premium gas to prevent knocking and have been struggling to keep my
operating temps down. Thanks to a lot of help from this list I checked the
timing curves on my distributor and found that I had the wrong vacuum
advance. The Toronado distributor I was using had a 27 degree vacuum
advance. After installing a new 10 degree vacuum advance (Delco 1973577) I
can now run regular gas and have solved the overheating problem. This
weekend was a good test of the cooling system. I was running through the
hills of Pennsylvania and the engine temp never exceeded 160 degrees, even
running uphill with full dash air.

I don't have any hard data to prove it but I suspect that the lower engine
temps probably keep the trans temps lower too. If I can find the time I
will be installing a trans temp gauge this summer so I can gather more facts.

Dave
73 Sequoia
 
Hi Dave, Thanks for the info. I believe the engine is stock its a rebuilt
from Spartan engine supply with about 6000mi. ordered and installed by a GMC
dealer in AZ. I do have the points ignition. I gave the Pumpkin-Rose a
tune-up before leaving Checked timing/dwell before any change, timing was
set at about 4deg. and dwell at 24 with RPM @ 1100 vac disconnected, after
change to platinum plugs(.040, old plugs were set alittle smaller) and some
new points/cap/rotor and wires adjusted to 8deg. timing / 30 on dwell. also
installed 4" dryer duct carb induction to grill. I did have more power, but
seemed to increase eng. temp. ( think putting timing/dwell back to spec.
would cause a temp increase? previous owner said gap/timing&dwell was set
for max cooling?) but hard to tell since first drive was in about 108outside
temps and after changes outside temps. were in the 118deg. range. Not sure
if I have a H.D. fan clutch but it does cut in/out at about the 195/200
range. Thermostat is stock @ 195.
At this time not sure if I want to go down to the 160 range, But know that I
would like to keep it off of the half mark (OEM gauge) on the longer hills
with outside temps at the 120 range if possible (Temps when planned travel
to CA. For Raiders games). Rad. looks good and clean in/out it does have a
diamond shape screen on grill heard this might restrict some air? Also have
vac. Tk. in front of Rad. cross member(between member/Rad.) with alum. rock
guard at bottom. I did another air induction to this area with rain gutters
to add air to lower rad. area unsure if it helped any. Also planning to
flush Rad./eng before next trip in a month. And adding more air ducts to
engine area. Anyhow just reading and learning how to keep our Pumpkin-rose
cruising. Thanks for any and all help.

Ron&Gina
73 Pumpkin-Rose
Fort Mohave, AZ
- -----Original Message-----
From: Dave
To: gmcmotorhome
Date: Tuesday, July 06, 1999 7:36 AM
Subject: Re: GMC: Frist trip/cooling tips

> >Just back from our short trip to Ca. from AZ. ... any tips to
> >improve engine& tranny temps? Thanks and keep on GMCing.
>
>I have been very aggressive at keeping my operating temps low. I like to
>run my engines at 160 degrees and do whatever it takes to keep them there.
>You may or may not want to be that aggressive but here is how I did it...
>
>1) Install Robertshaw 160 degree thermostat (P/N 330-160 I think).
>
>2) Install a heavy duty fan clutch. If it still allows the operating temp
>to go over 160 degrees (mine did) then adjust the thermostat on the fan
>clutch. This can be done by making a new slot in the bracket that holds the
>outer end of the thermostat coil and moving the fixed end of the coil to
>the new slot. I adjusted mine so it starts to engage at 75 degrees outside
>temp (with the dash A/C turned on).
>
>3) Check your timing and the timing advance curves. If you still have the
>older points style ignition, be sure its tuned up properly. The ignition on
>our 73's all used the breaker point style distributor. If your engine has
>electronic ignition then it has been upgraded and there is a good chance
>that you may not have the correct distributor.
>
>I learned that the timing curves are very critical. For years I had to use
>premium gas to prevent knocking and have been struggling to keep my
>operating temps down. Thanks to a lot of help from this list I checked the
>timing curves on my distributor and found that I had the wrong vacuum
>advance. The Toronado distributor I was using had a 27 degree vacuum
>advance. After installing a new 10 degree vacuum advance (Delco 1973577) I
>can now run regular gas and have solved the overheating problem. This
>weekend was a good test of the cooling system. I was running through the
>hills of Pennsylvania and the engine temp never exceeded 160 degrees, even
>running uphill with full dash air.
>
>I don't have any hard data to prove it but I suspect that the lower engine
>temps probably keep the trans temps lower too. If I can find the time I
>will be installing a trans temp gauge this summer so I can gather more
facts.
>
>Dave
>73 Sequoia
>
 
>Hi Dave, Thanks for the info. ... I did have more power, but
>seemed to increase eng. temp. ( think putting timing/dwell back to spec.
>would cause a temp increase? previous owner said gap/timing&dwell was set
>for max cooling?)

Check to be sure the centrifugal advance and the vacuum advance are
working. If they are not, that may cause it to run hotter. I don't remember
the advance numbers for the original (points style) distributor but they
are in the service manual. I don't have my copy handy but I can look up the
numbers for you this weekend if you don't have a copy.

Dave
73 Sequoia
 
I believe they are working!! But will check again. And I do have the
manuals.
Thanks Your opinion on 4, 6-ton stands holding up the sweet lady?

Ron&Gina
73 Pumpkin-rose
Fort Mohave,AZ

- -----Original Message-----
From: Dave
To: gmcmotorhome
Date: Tuesday, July 06, 1999 6:16 PM
Subject: Re: GMC: Frist trip/cooling tips

> >Hi Dave, Thanks for the info. ... I did have more power, but
> >seemed to increase eng. temp. ( think putting timing/dwell back to spec.
> >would cause a temp increase? previous owner said gap/timing&dwell was
set
> >for max cooling?)
>
>Check to be sure the centrifugal advance and the vacuum advance are
>working. If they are not, that may cause it to run hotter. I don't remember
>the advance numbers for the original (points style) distributor but they
>are in the service manual. I don't have my copy handy but I can look up the
>numbers for you this weekend if you don't have a copy.
>
>Dave
>73 Sequoia
>
 
>I believe they are working!! But will check again. And I do have the
>manuals.

Sounds like they probably are. At 118 degrees outside air temp the cooling
system is probably working pretty well if you are not overheating. Thats a
reasonably good test of just about any cooling system...

>Thanks Your opinion on 4, 6-ton stands holding up the sweet lady?

Maybe a little heavy in the rear for a 6 ton stand. I like lots of extra
strength before I crawl under something. Also I am not sure where there is
enough strength to support the rear on a jack stand. I assume you will be
jacking under the bogies.

I use a couple of homemade ramps in the rear. They are made of 2x12's
nailed in a stack. I raise the rear airbags for clearance, drive up on the
ramps and then block up the rear bogies (in case I break an air line). If I
need the front up at the same time I use a floor jack on the main cross
member and a couple of jack stands for safety. Lots of room to work when
she is in that position.

Dave
73 Sequoia
 
I'll raise with bottle jack and hook. which still leaves room to put stand
on bottom of bogie support. But just thinking whats safe. Might make wooden
ramps but seems quite heavy to move around. Thanks again

Ron

- ----- Original Message -----
From: Dave
To:
Sent: Tuesday, July 06, 1999 6:53 PM
Subject: Re: GMC: Frist trip/cooling tips

> >I believe they are working!! But will check again. And I do have the
> >manuals.
>
> Sounds like they probably are. At 118 degrees outside air temp the cooling
> system is probably working pretty well if you are not overheating. Thats a
> reasonably good test of just about any cooling system...
>
> >Thanks Your opinion on 4, 6-ton stands holding up the sweet lady?
>
> Maybe a little heavy in the rear for a 6 ton stand. I like lots of extra
> strength before I crawl under something. Also I am not sure where there is
> enough strength to support the rear on a jack stand. I assume you will be
> jacking under the bogies.
>
> I use a couple of homemade ramps in the rear. They are made of 2x12's
> nailed in a stack. I raise the rear airbags for clearance, drive up on the
> ramps and then block up the rear bogies (in case I break an air line). If
I
> need the front up at the same time I use a floor jack on the main cross
> member and a couple of jack stands for safety. Lots of room to work when
> she is in that position.
>
> Dave
> 73 Sequoia
>
 
Ron,
Another simple and very inexpensive method of getting the low slung beast up in
the air is to cut up a couple of 2x6's and nailing them into a ramp about about
5 or 6 pieces high. I have 2 sets, 1 a little higher than the other. If I'm
working under the back, I put the taller of the ramps behind the back wheels and
the shorter pair behind the front wheels and drive up on them - having someone
guide me. It's a little tricky the first time. It's also a good idea to remove
ypour rear t-skirts first, if you are going to stay up a long time. Then I also
put a couple of 6x6 blocks underthe bogies (that I use any time I'm home and
going to be parked for more than a few hours.) This allows me room to get under
on a creeper.

Wayne Newland F9300 75 Palm Beach

>
> > Your opinion on 4, 6-ton stands holding up the sweet lady?
> >
>
> Ron,
> Should be adequate IMHO. MY '75 is in the driveway on 4 little 3 ton
> stands right now. Trouble with most 6 ton stands is they're too tall for
> safety or ease of use. Biggest factor to consider is what is your driveway
> made of? Recommend 6" thick or reinforced concrete. Asphalt is iffy, esp if
> hot. If you must use asphalt, put a piece of 3/4" or thicker plywood under
> the stands and see how it sits for a few hours. Don't use them if the stands
> sink into the wood.
> Only once (many years ago) in 30+ years of car repair did a car almost
> crush me, and that was using big wooden blocks (actually ~1'+ diameter X ~1'
> long tree stumps) as supports. They were plenty strong, but they sank into
> the soft ground, and I slid myself out just as they rolled over and the car
> went "whump" onto the ground. Cleaning out my shorts, I adopted my backup
> safety method I still use today: When working under any vehicle on stands, I
> place a wheel (tire and all) on its side under the frame, adjacent to where
> I'm working. If disaster DOES happen, it will limit the damage/injury.
> My GMC did roll off its stands once as I lowered it, but that was because
> the brakes were off and I had forgotten to chock it. As the rear wheels
> reached the ground, it rolled down my sloping driveway, and off of the
> slightly tall/small-based front stands. Once again, the main danger is
> falling off the stands, not stands collapsing. Whatever you do, place them
> carefully (I go under the bogie supports in back, under the crossmember in
> front), and try to push the vehicle off the stands before getting under it.
> Good luck, and let's be careful out there!
>
> Rick Staples
> '75 Eleganza
> Louisville, CO
 
Hi and thanks for info Wayne, I just got the Lady's rear up on 6-ton stands
and hyd. jacks? no shakes yet. Was trying to find/put together blocks for
added safety. Think I will make up some wooden ramps. The old Lady looks
heavy in the rear, But real nice!! Thanks again

Ron&Gina
73 Pumpkin-Rose
Fort Mohave,AZ

- ----- Original Message -----
From: Wayne Newland
To:
Sent: Wednesday, July 07, 1999 6:51 AM
Subject: Re: GMC: Frist trip/cooling tips

> Ron,
> Another simple and very inexpensive method of getting the low slung beast
up in
> the air is to cut up a couple of 2x6's and nailing them into a ramp about
about
> 5 or 6 pieces high. I have 2 sets, 1 a little higher than the other. If
I'm
> working under the back, I put the taller of the ramps behind the back
wheels and
> the shorter pair behind the front wheels and drive up on them - having
someone
> guide me. It's a little tricky the first time. It's also a good idea to
remove
> ypour rear t-skirts first, if you are going to stay up a long time. Then
I also
> put a couple of 6x6 blocks underthe bogies (that I use any time I'm home
and
> going to be parked for more than a few hours.) This allows me room to get
under
> on a creeper.
>
> Wayne Newland F9300 75 Palm Beach
>

>

> >
> > > Your opinion on 4, 6-ton stands holding up the sweet lady?
> > >
> >
> > Ron,
> > Should be adequate IMHO. MY '75 is in the driveway on 4 little 3 ton
> > stands right now. Trouble with most 6 ton stands is they're too tall
for
> > safety or ease of use. Biggest factor to consider is what is your
driveway
> > made of? Recommend 6" thick or reinforced concrete. Asphalt is iffy,
esp if
> > hot. If you must use asphalt, put a piece of 3/4" or thicker plywood
under
> > the stands and see how it sits for a few hours. Don't use them if the
stands
> > sink into the wood.
> > Only once (many years ago) in 30+ years of car repair did a car
almost
> > crush me, and that was using big wooden blocks (actually ~1'+ diameter X
~1'
> > long tree stumps) as supports. They were plenty strong, but they sank
into
> > the soft ground, and I slid myself out just as they rolled over and the
car
> > went "whump" onto the ground. Cleaning out my shorts, I adopted my
backup
> > safety method I still use today: When working under any vehicle on
stands, I
> > place a wheel (tire and all) on its side under the frame, adjacent to
where
> > I'm working. If disaster DOES happen, it will limit the damage/injury.
> > My GMC did roll off its stands once as I lowered it, but that was
because
> > the brakes were off and I had forgotten to chock it. As the rear wheels
> > reached the ground, it rolled down my sloping driveway, and off of the
> > slightly tall/small-based front stands. Once again, the main danger is
> > falling off the stands, not stands collapsing. Whatever you do, place
them
> > carefully (I go under the bogie supports in back, under the crossmember
in
> > front), and try to push the vehicle off the stands before getting under
it.
> > Good luck, and let's be careful out there!
> >
> > Rick Staples
> > '75 Eleganza
> > Louisville, CO
>
>
>
 
I had my 26' GMC up on 4 little jacks,
I think they were 3 ton jacks. Anyway,
I had it up on stands for a week or two
then went to let it down. First one of the jacks under the rear bogie bent
then the
one up front on the other side. I went
straight to autozone and got a 6ton set.
I'm NEVER getting under there again with
anything less. That coach came down in a hurry!
Be Safe.
Rob Teed 74 Painted Desert

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailto:owner-gmcmotorhome]On Behalf Of
> RickStapls
> Sent: Wednesday, July 07, 1999 2:38 AM
> To: gmcmotorhome
> Subject: Re: GMC: Frist trip/cooling tips
>
>

>
> > Your opinion on 4, 6-ton stands holding up the sweet lady?
> >
>
> Ron,
> Should be adequate IMHO. MY '75 is in the driveway on 4 little 3 ton
> stands right now. Trouble with most 6 ton stands is they're too tall for
> safety or ease of use. Biggest factor to consider is what is
> your driveway
> made of? Recommend 6" thick or reinforced concrete. Asphalt is
> iffy, esp if
> hot. If you must use asphalt, put a piece of 3/4" or thicker
> plywood under
> the stands and see how it sits for a few hours. Don't use them
> if the stands
> sink into the wood.
> Only once (many years ago) in 30+ years of car repair did a car almost
> crush me, and that was using big wooden blocks (actually ~1'+
> diameter X ~1'
> long tree stumps) as supports. They were plenty strong, but they
> sank into
> the soft ground, and I slid myself out just as they rolled over
> and the car
> went "whump" onto the ground. Cleaning out my shorts, I adopted
> my backup
> safety method I still use today: When working under any vehicle
> on stands, I
> place a wheel (tire and all) on its side under the frame,
> adjacent to where
> I'm working. If disaster DOES happen, it will limit the damage/injury.
> My GMC did roll off its stands once as I lowered it, but that
> was because
> the brakes were off and I had forgotten to chock it. As the rear wheels
> reached the ground, it rolled down my sloping driveway, and off of the
> slightly tall/small-based front stands. Once again, the main danger is
> falling off the stands, not stands collapsing. Whatever you do,
> place them
> carefully (I go under the bogie supports in back, under the
> crossmember in
> front), and try to push the vehicle off the stands before getting
> under it.
> Good luck, and let's be careful out there!
>
> Rick Staples
> '75 Eleganza
> Louisville, CO
>

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