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Oil Pressure Poll

GC
Greg Crawford
Wed, Sep 8, 2021 12:54 AM

So today I got my Autometer oil pressure gauge hooked up. I also have the factory gauge, with a NOS Made In USA Echlin OP6636 sender. I'm currently
running 10-30 synthetic oil. Today's temperature was about 82. I started up the engine so I could run my new Viair compressor and evaluate its
performance.

On start up, my stock gauge showed a little bit above halfway, and the Autometer gauge showed about (no exact corresponding lines) 30-32 PSI at about
900 RPM. After running a bit and kicking off the fast idle, the Autometer showed 25 PSI @ 650 RPM and 180 degrees water temp.

I went back and messed around with the compressor and checked for leaks for a few minutes. Going back into the cockpit showed 195-200 degrees and
about 12-13 PSI of oil pressure at 650 RPM. Revving up to 1500 RPM netted about 30 PSI.

Those of you who have aftermarket gauges, how does this compare to yours?

Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

So today I got my Autometer oil pressure gauge hooked up. I also have the factory gauge, with a NOS Made In USA Echlin OP6636 sender. I'm currently running 10-30 synthetic oil. Today's temperature was about 82. I started up the engine so I could run my new Viair compressor and evaluate its performance. On start up, my stock gauge showed a little bit above halfway, and the Autometer gauge showed about (no exact corresponding lines) 30-32 PSI at about 900 RPM. After running a bit and kicking off the fast idle, the Autometer showed 25 PSI @ 650 RPM and 180 degrees water temp. I went back and messed around with the compressor and checked for leaks for a few minutes. Going back into the cockpit showed 195-200 degrees and about 12-13 PSI of oil pressure at 650 RPM. Revving up to 1500 RPM netted about 30 PSI. Those of you who have aftermarket gauges, how does this compare to yours? -- Greg Crawford KM4ZCR Knoxville, TN "Ruby Sue" 1977 Royale Rear Bath 403 Engine American Eagle Wheels Early Version Alex Sirum Quad bags
GC
Greg Crawford
Wed, Sep 8, 2021 12:58 AM

Another interesting fact. I have never heard my (new) clutch fan kick in other than at the first crank of the day.

Today, while watching the gauges at idle, the temp climbed to 205 degrees.

I have a new core in the stock radiator, a heavy duty fan clutch, and a Robert Shaw 195 degree thermostat, tested on the stove before install.

While I watched the gauge, the fan kicked in at 205 degrees indicated, and ran until the temp gauge dropped to 180 degrees. I was impressed. And
relieved that the fan seems to be working correctly.

Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

Another interesting fact. I have never heard my (new) clutch fan kick in other than at the first crank of the day. Today, while watching the gauges at idle, the temp climbed to 205 degrees. I have a new core in the stock radiator, a heavy duty fan clutch, and a Robert Shaw 195 degree thermostat, tested on the stove before install. While I watched the gauge, the fan kicked in at 205 degrees indicated, and ran until the temp gauge dropped to 180 degrees. I was impressed. And relieved that the fan seems to be working correctly. -- Greg Crawford KM4ZCR Knoxville, TN "Ruby Sue" 1977 Royale Rear Bath 403 Engine American Eagle Wheels Early Version Alex Sirum Quad bags
JK
Jim Kanomata
Wed, Sep 8, 2021 12:58 AM

Greg,
How many miles are on the engine.

On Tue, Sep 7, 2021 at 5:54 PM Greg Crawford captgregcrawford@gmail.com
wrote:

So today I got my Autometer oil pressure gauge hooked up. I also have the
factory gauge, with a NOS Made In USA Echlin OP6636 sender. I'm currently
running 10-30 synthetic oil. Today's temperature was about 82. I started
up the engine so I could run my new Viair compressor and evaluate its
performance.

On start up, my stock gauge showed a little bit above halfway, and the
Autometer gauge showed about (no exact corresponding lines) 30-32 PSI at
about
900 RPM. After running a bit and kicking off the fast idle, the Autometer
showed 25 PSI @ 650 RPM and 180 degrees water temp.

I went back and messed around with the compressor and checked for leaks
for a few minutes. Going back into the cockpit showed 195-200 degrees and
about 12-13 PSI of oil pressure at 650 RPM. Revving up to 1500 RPM netted
about 30 PSI.

Those of you who have aftermarket gauges, how does this compare to yours?

Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags


GMCnet mailing list
Unsubscribe or Change List Options:

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502

Greg, How many miles are on the engine. On Tue, Sep 7, 2021 at 5:54 PM Greg Crawford <captgregcrawford@gmail.com> wrote: > So today I got my Autometer oil pressure gauge hooked up. I also have the > factory gauge, with a NOS Made In USA Echlin OP6636 sender. I'm currently > running 10-30 synthetic oil. Today's temperature was about 82. I started > up the engine so I could run my new Viair compressor and evaluate its > performance. > > On start up, my stock gauge showed a little bit above halfway, and the > Autometer gauge showed about (no exact corresponding lines) 30-32 PSI at > about > 900 RPM. After running a bit and kicking off the fast idle, the Autometer > showed 25 PSI @ 650 RPM and 180 degrees water temp. > > I went back and messed around with the compressor and checked for leaks > for a few minutes. Going back into the cockpit showed 195-200 degrees and > about 12-13 PSI of oil pressure at 650 RPM. Revving up to 1500 RPM netted > about 30 PSI. > > Those of you who have aftermarket gauges, how does this compare to yours? > -- > Greg Crawford > KM4ZCR > Knoxville, TN > > "Ruby Sue" > 1977 Royale > Rear Bath > 403 Engine > American Eagle Wheels > Early Version Alex Sirum Quad bags > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: > -- Jim Kanomata ASE Applied/GMC, Newark,CA jimk@appliedairfilters.com http://www.gmcrvparts.com 1-800-752-7502
CS
Carl Stouffer
Wed, Sep 8, 2021 1:15 AM

The machine work on my engine was done at Larry's Engine and Marine here in Tucson.  Larry has extensive experience with Olds 455 engines, having
built literally hundreds of them over the years for jet boat and hot rod applications.  He understood the motorhome application and provided machine
shop and parts services accordingly.  The bearing clearances were set up specifically for 20W50 oil due mostly to the giant size of the main journals
on the crankshaft of a 455.  This was Larry's recommendation.  I had already been running 20W50 oil, at Jim Bounds' suggestion before the rebuild.

Last year, about this time, we embarked on a 3500 mile trip to The Grand Tetons, Yellowstone, Devil's Tower, Rapid City, and back through several
Wyoming and Utah national parks and monuments.  Right before that trip, I had decided to experiment with 15W40 Rotella oil instead of the Valvoline
20W50 I had been using.  I noticed my oil pressure running lower than usual as a result and stressed about it for most of the trip.  I changed back to
the 20W50 and the oil pressure (on the stock gauge)returned to what it had been before.  I won't run anything in it but 20W50 again.

Maybe you need to run a heavier oil in it, at least 15W40, if not 20W50.

Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging.  GMCSJ and GMCMI member

The machine work on my engine was done at Larry's Engine and Marine here in Tucson. Larry has extensive experience with Olds 455 engines, having built literally hundreds of them over the years for jet boat and hot rod applications. He understood the motorhome application and provided machine shop and parts services accordingly. The bearing clearances were set up specifically for 20W50 oil due mostly to the giant size of the main journals on the crankshaft of a 455. This was Larry's recommendation. I had already been running 20W50 oil, at Jim Bounds' suggestion before the rebuild. Last year, about this time, we embarked on a 3500 mile trip to The Grand Tetons, Yellowstone, Devil's Tower, Rapid City, and back through several Wyoming and Utah national parks and monuments. Right before that trip, I had decided to experiment with 15W40 Rotella oil instead of the Valvoline 20W50 I had been using. I noticed my oil pressure running lower than usual as a result and stressed about it for most of the trip. I changed back to the 20W50 and the oil pressure (on the stock gauge)returned to what it had been before. I won't run anything in it but 20W50 again. Maybe you need to run a heavier oil in it, at least 15W40, if not 20W50. -- Carl Stouffer '75 ex Palm Beach Tucson, AZ. Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
JR
John R. Lebetski
Wed, Sep 8, 2021 1:34 AM

Heavy oil makes gauge read higher because there is less flow. Flow is what cools bearings, pistons and valvetrain. As long as you are over 10 PSI per
1000 rpm you should be ok.  Above 60 PSI the bypass starts to open anyway. The vented oil goes back to pump inlet instead of to parts where it can
lube and clean and cool them. Paraphrasing Dick Patterson’s Olds oiling  presentation.

John Lebetski
Woodstock, IL
77 Eleganza II

Heavy oil makes gauge read higher because there is less flow. Flow is what cools bearings, pistons and valvetrain. As long as you are over 10 PSI per 1000 rpm you should be ok. Above 60 PSI the bypass starts to open anyway. The vented oil goes back to pump inlet instead of to parts where it can lube and clean and cool them. Paraphrasing Dick Patterson’s Olds oiling presentation. -- John Lebetski Woodstock, IL 77 Eleganza II
L
Larry
Wed, Sep 8, 2021 3:26 AM

The one thing I have learned is that with today’s oils, thicker is not better. IMO, it is best to use as thin of an oil as possible,  that gives you
acceptable hot oil pressure. The thinner it is, the more oil you have going to bearings, reducing wear. The thinner it is the more oil is carrying
heat away from moving parts. The thinner it is at cold temps, the quicker oil gets to the bearing surfaces reducing wear. The thinner it is at cold
temps, the more oil you have actually going to those cold surfaces quicker, reducing wear. I use the 0W40 mainly because the “0” flows for my
Wisconsin cold winter starts, (sometimes we leave for the south in -15*) while giving me the “40” for acceptable oil pressure on hot running. On
cold starts, I have oil pressure immediately with the "0", and 45-48lbs hot running down the road, and 30lbs and a hot idle. I think it is Matt C.
that once said, the only down side is the “0” also has a run-off factor when sitting for long periods, meaning because of the low viscosity, it
runs off easier than the 5w to 15w weights when sitting for long periods. If my coach has been sitting for more than a couple of months, I get by that
by pulling the ignition wire and turning the engine over until I see the needle move on the oil pressure gauge….then hook up the wire and start. A
minor inconvenience but IMO worth the effort.

I think it was Matt that said that it is hard to find a "bad" oil out there, so to my way of thinking, if you have engineering and scientific testing
that shows certain oils are better than others in reducing wear, why not go with it.

Oils have improved immensely over the years. Todays knowledge of chemistry and engineering have created oil blends that give us oils that far exceed
the wear characteristics of yesterday’s blends. Todays blends have chemical replacement elements that duplicate the elements of ZDDP, so there may
be only traces or no ZDDP in the oil, yet have extremely high wear characteristics. These oils have been formulated to assist todays engines in
meeting EPA standards. Since most of us are not experts in the wear characteristics of oil, we act on what we know from our past knowledge and
experiences. The past is behind us and while relevant, we need to look at present engineering going into the future. I’ve done as much as my pea
brain will tolerate in researching the best oil for my Cad 500. So far the best I have found is a blog by a guy that calls himself 540Rat. He has
taken the time using engineering techniques to test over 240 different oil blends, and ranked them by their ability to resist wear.

https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/

This is a tough read filled with testing, engineering data, a lot of self praise/bluster, and a lot of information that we don’t need, but is the
best I have found to help me in my decisions relative to the oils that I am using in my vehicles. While it would be best to read most of the beginning
info, for the meat of the blog, grab the scroll button and scroll about 1/10 of the way down to “WEAR PROTECTION RANKING LIST”. This lists oil in
their ability to resist wear by measuring in psi their ability to keep metals from making contact. It should be noted that while he has tested an
number of them ranked very high on this list that have an aftermarket oil additive, he does NOT endorse the use of oil additives claiming that you
really don’t know what you are doing to the carefully engineered chemical blend when you pour in these additives. So he claims it is best to choose
an oil that ranks high on the list straight out of the bottle.

The Wear Protection reference categories are:

  • Over 150,000 psi = SPECTACULAR wear protection
  • 135,000 psi to 150,000 psi = AMAZING wear protection
  • 120,000 psi = FANTASTIC wear protection
  • 105,000 to 120,000 psi = INCREDIBLE wear protection
  • 90,000 to 105,000 psi = OUTSTANDING wear protection
  • 75,000 to 90,000 psi = GOOD wear protection
  • 60,000 to 75,000 psi = MODERATE wear protection
  • 50,000 to 60,000 psi = UNDESIRABLE LOW wear protection
  • Below 50,000 psi = CAUTION – EXTREMELY LOW wear protection
    The HIGHER the psi value, the BETTER the Wear Protection.

I personally use # 1 5W30 Quaker State “Full Synthetic” = 152,674 psi.  in my automobiles and #15. 0W40 Mobil 1 “FS” European Car Formula,
synthetic = 127,221 psi, in my motorhome.

If you want to see where the oil you have been using ranks, do a command F or Control F, type in the brand of oil, and hit CR to advance through the
article until you find it. Some of the oils that have been the staple of the GMC community for years are surprisingly low on the wear protection
list.

Sooooo….judge for yourself. Choose wisely by making informed choices.
JMHO

Larry
78 Royale w/500 Caddy
Menomonie, WI.

The one thing I have learned is that with today’s oils, thicker is not better. IMO, it is best to use as thin of an oil as possible, that gives you acceptable hot oil pressure. The thinner it is, the more oil you have going to bearings, reducing wear. The thinner it is the more oil is carrying heat away from moving parts. The thinner it is at cold temps, the quicker oil gets to the bearing surfaces reducing wear. The thinner it is at cold temps, the more oil you have actually going to those cold surfaces quicker, reducing wear. I use the 0W40 mainly because the “0” flows for my Wisconsin cold winter starts, (sometimes we leave for the south in -15*) while giving me the “40” for acceptable oil pressure on hot running. On cold starts, I have oil pressure immediately with the "0", and 45-48lbs hot running down the road, and 30lbs and a hot idle. I think it is Matt C. that once said, the only down side is the “0” also has a run-off factor when sitting for long periods, meaning because of the low viscosity, it runs off easier than the 5w to 15w weights when sitting for long periods. If my coach has been sitting for more than a couple of months, I get by that by pulling the ignition wire and turning the engine over until I see the needle move on the oil pressure gauge….then hook up the wire and start. A minor inconvenience but IMO worth the effort. I think it was Matt that said that it is hard to find a "bad" oil out there, so to my way of thinking, if you have engineering and scientific testing that shows certain oils are better than others in reducing wear, why not go with it. Oils have improved immensely over the years. Todays knowledge of chemistry and engineering have created oil blends that give us oils that far exceed the wear characteristics of yesterday’s blends. Todays blends have chemical replacement elements that duplicate the elements of ZDDP, so there may be only traces or no ZDDP in the oil, yet have extremely high wear characteristics. These oils have been formulated to assist todays engines in meeting EPA standards. Since most of us are not experts in the wear characteristics of oil, we act on what we know from our past knowledge and experiences. The past is behind us and while relevant, we need to look at present engineering going into the future. I’ve done as much as my pea brain will tolerate in researching the best oil for my Cad 500. So far the best I have found is a blog by a guy that calls himself 540Rat. He has taken the time using engineering techniques to test over 240 different oil blends, and ranked them by their ability to resist wear. https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/ This is a tough read filled with testing, engineering data, a lot of self praise/bluster, and a lot of information that we don’t need, but is the best I have found to help me in my decisions relative to the oils that I am using in my vehicles. While it would be best to read most of the beginning info, for the meat of the blog, grab the scroll button and scroll about 1/10 of the way down to “WEAR PROTECTION RANKING LIST”. This lists oil in their ability to resist wear by measuring in psi their ability to keep metals from making contact. It should be noted that while he has tested an number of them ranked very high on this list that have an aftermarket oil additive, he does NOT endorse the use of oil additives claiming that you really don’t know what you are doing to the carefully engineered chemical blend when you pour in these additives. So he claims it is best to choose an oil that ranks high on the list straight out of the bottle. The Wear Protection reference categories are: * Over 150,000 psi = SPECTACULAR wear protection * 135,000 psi to 150,000 psi = AMAZING wear protection * 120,000 psi = FANTASTIC wear protection * 105,000 to 120,000 psi = INCREDIBLE wear protection * 90,000 to 105,000 psi = OUTSTANDING wear protection * 75,000 to 90,000 psi = GOOD wear protection * 60,000 to 75,000 psi = MODERATE wear protection * 50,000 to 60,000 psi = UNDESIRABLE LOW wear protection * Below 50,000 psi = CAUTION – EXTREMELY LOW wear protection The HIGHER the psi value, the BETTER the Wear Protection. I personally use # 1 5W30 Quaker State “Full Synthetic” = 152,674 psi. in my automobiles and #15. 0W40 Mobil 1 “FS” European Car Formula, synthetic = 127,221 psi, in my motorhome. If you want to see where the oil you have been using ranks, do a command F or Control F, type in the brand of oil, and hit CR to advance through the article until you find it. Some of the oils that have been the staple of the GMC community for years are surprisingly low on the wear protection list. Sooooo….judge for yourself. Choose wisely by making informed choices. JMHO -- Larry 78 Royale w/500 Caddy Menomonie, WI.
GC
Greg Crawford
Wed, Sep 8, 2021 11:20 AM

Jim, the engine has 67,000 miles.

Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

Jim, the engine has 67,000 miles. -- Greg Crawford KM4ZCR Knoxville, TN "Ruby Sue" 1977 Royale Rear Bath 403 Engine American Eagle Wheels Early Version Alex Sirum Quad bags
GC
Greg Crawford
Wed, Sep 8, 2021 1:45 PM

Larry, I have read the 540 Rat blog a few times. I'm running Quaker State Ultimate Durability after reading his blog. Maybe I need to change to
10W40.

Thank you for taking the time to respond with all that information.

Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

Larry, I have read the 540 Rat blog a few times. I'm running Quaker State Ultimate Durability after reading his blog. Maybe I need to change to 10W40. Thank you for taking the time to respond with all that information. -- Greg Crawford KM4ZCR Knoxville, TN "Ruby Sue" 1977 Royale Rear Bath 403 Engine American Eagle Wheels Early Version Alex Sirum Quad bags
BM
Billy Massey
Wed, Sep 8, 2021 1:55 PM

Thanks very much for this, Larry.  Very interesting and changed my thinking
on oil pressure.

I'll try it.  I'm due an oil change on two other of my high
mileage vehicles AND the GMC.

:-)
bdub

On Tue, Sep 7, 2021 at 10:26 PM Larry weidnerl@wwt.net wrote:

The one thing I have learned is that with today’s oils, thicker is not
better. IMO, it is best to use as thin of an oil as possible,  that gives
you acceptable hot oil pressure.
... snip ...

Thanks very much for this, Larry. Very interesting and changed my thinking on oil pressure. I'll try it. I'm due an oil change on two other of my high mileage vehicles AND the GMC. :-) bdub On Tue, Sep 7, 2021 at 10:26 PM Larry <weidnerl@wwt.net> wrote: > The one thing I have learned is that with today’s oils, thicker is not > better. IMO, it is best to use as thin of an oil as possible, that gives > you acceptable hot oil pressure. > ... snip ... >
JK
Jim Kanomata
Wed, Sep 8, 2021 4:44 PM

My experience is that the pressure can decrease after the engine reaches
over 50.000 miles and also how long the engine sat around.

On Wed, Sep 8, 2021 at 6:55 AM Billy Massey bdub.bdub@gmail.com wrote:

Thanks very much for this, Larry.  Very interesting and changed my thinking
on oil pressure.

I'll try it.  I'm due an oil change on two other of my high
mileage vehicles AND the GMC.

:-)
bdub

On Tue, Sep 7, 2021 at 10:26 PM Larry weidnerl@wwt.net wrote:

The one thing I have learned is that with today’s oils, thicker is not
better. IMO, it is best to use as thin of an oil as possible,  that gives
you acceptable hot oil pressure.
... snip ...


GMCnet mailing list
Unsubscribe or Change List Options:

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502

My experience is that the pressure can decrease after the engine reaches over 50.000 miles and also how long the engine sat around. On Wed, Sep 8, 2021 at 6:55 AM Billy Massey <bdub.bdub@gmail.com> wrote: > Thanks very much for this, Larry. Very interesting and changed my thinking > on oil pressure. > > I'll try it. I'm due an oil change on two other of my high > mileage vehicles AND the GMC. > > :-) > bdub > > > On Tue, Sep 7, 2021 at 10:26 PM Larry <weidnerl@wwt.net> wrote: > > > The one thing I have learned is that with today’s oils, thicker is not > > better. IMO, it is best to use as thin of an oil as possible, that gives > > you acceptable hot oil pressure. > > ... snip ... > > > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: > -- Jim Kanomata ASE Applied/GMC, Newark,CA jimk@appliedairfilters.com http://www.gmcrvparts.com 1-800-752-7502