The Olds 403/455 were an out standing choice for our GMC's

[Bob Dunahugh]

I've built many V8's of many sizes, and manufactures. These Olds engines have a very stable main bearing web area.
They've performed well. The problems experienced by GMC owners are. For the most part have been self inflicted. Our first GMC that burned had 154,000 miles on it. According to the log book. The 403 had never been apart except for a timing gear replacement that I did. Used a qt of oil by the time of an oil change. At 3,000 miles. Good oil pressure. With compression readings of 145 to 150 PSI. Always had mineral oil used. This is what you get out of a well maintained 403/455. Blame the owner. That's the problem. Not the engine. Bob Dunahugh 78 Royale Iowa.

 

[john phillips]

So What do we do to kill them?
John Phillips
75 Avion VIN A26000
Retired
Rancho Cordova, CA 95670

On Sun, Mar 31, 2019 at 9:58 PM Bob Dunahugh via Gmclist <

> I've built many V8's of many sizes, and manufactures. These Olds engines
> have a very stable main bearing web area.
> They've performed well. The problems experienced by GMC owners are. For
> the most part have been self inflicted. Our first GMC that burned had
> 154,000 miles on it. According to the log book. The 403 had never been
> apart except for a timing gear replacement that I did. Used a qt of oil by
> the time of an oil change. At 3,000 miles. Good oil pressure. With
> compression readings of 145 to 150 PSI. Always had mineral oil used. This
> is what you get out of a well maintained 403/455. Blame the owner. That's
> the problem. Not the engine. Bob Dunahugh 78 Royale Iowa.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*

 

[johnny]

Letting Jasper rebuild them is a good start on killing them.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[kingsley coach]

lol

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On Mon, Apr 1, 2019 at 10:03 AM Johnny Bridges via Gmclist <

> Letting Jasper rebuild them is a good start on killing them.
>
> --johnny
> --
> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> "I forgive them all, save those who hurt the dogs. They must answer to me
> in hell" - ol Andy, paraphrased
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Michael Beaton
1977 Kingsley 26-11
1977 Eleganza II 26-3
Antigonish, NS

Life is too short to hold a grudge; slash some tires and call it even !

 

[tmsnyder]

Assuming that the oil changes are regular, fuel and cooling systems are maintained, no toad, reasonable highway speeds, etc. Reasonable best case
scenario; what would be the expected life of a 455?

Is 100,000 miles pretty common?

What are the typical modes of failure? I read that spun rod bearings, and bent/stuck valves as being common modes of failure. Any truth to this?

Is there any collection of these data?
--
Todd Snyder, Buffalo NY
1976 Eleganza II

 

[roy keen]

In my opinion traveling in flat land country like Florida will add many miles to the engine life versus traveling in mostly mountain country in the
western mountain states with a toad in tow. A lot of lower gear higher rpm going up and down mountains is a work out for any heavy laden engine.
--
Roy Keen
Minden,NV
76 X Glenbrook

 

[Jim Hupy]

Based upon my personal experience of 40 years as a mechanic, much of it on
Olds engines dating back to 1949 with the 303 Rockets, then through the
various updates in the '50s, '60s, '70s, both in automotive and marine
usage, I can say that the high nickel content 455 Olds 455 blocks are as
close to bulletproof as a production engine can be, FOR THEIR ERA. They are
an under square design, small bore, long stroke, meaty cylinders, old
school design. The 403 is a more modern design, siamese cylinders in pairs,
oversquare in design.
Longevity? Subjectively difficult to compare because of the extreme duty
use in motorhomes. But, 100,000 miles on a 455 is reasonable to expect.
More on a 403, especially if you change the final drive gear ratio to a
3:70. No other GM engines will do that except 500 Cadillac.
Chev, Ford, Mopar, with the exception of the Canadian truck version of
the 413 - 440 engines with the gear driven cams, will match that. Your
opinions will vary.
Jim Hupy

On Fri, Apr 26, 2019, 8:13 AM Todd Snyder via Gmclist <

> Assuming that the oil changes are regular, fuel and cooling systems are
> maintained, no toad, reasonable highway speeds, etc. Reasonable best case
> scenario; what would be the expected life of a 455?
>
> Is 100,000 miles pretty common?
>
> What are the typical modes of failure? I read that spun rod bearings,
> and bent/stuck valves as being common modes of failure. Any truth to this?
>
> Is there any collection of these data?
> --
> Todd Snyder, Buffalo NY
> 1976 Eleganza II
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Jim Hupy]

The absolute worst workout for any engine is low rpm, high crankshaft
loading, large throttle opening, heavily laden use.
All other factors being equal, RPM's are free, as long as the piston
speed is reasonable. 4000 rpm is just fine. As long as the air/fuel mixture
is correct, and the cooling system is carrying away the heat faster than
you can make it. Goes without saying that the exhaust system needs to be up
to the task as well.
Jim Hupy
Salem, Oregon
78 GMC ROYALE 403

On Fri, Apr 26, 2019, 8:35 AM roy keen via Gmclist
wrote:

> In my opinion traveling in flat land country like Florida will add many
> miles to the engine life versus traveling in mostly mountain country in the
> western mountain states with a toad in tow. A lot of lower gear higher rpm
> going up and down mountains is a work out for any heavy laden engine.
> --
> Roy Keen
> Minden,NV
> 76 X Glenbrook
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[tmsnyder]

Is there any benefit to the TH425 with a higher engine rpm? Or is this transmission pretty bulletproof?
--
Todd Snyder, Buffalo NY
1976 Eleganza II

 

[jeremy]

It's a robust transmission though the motorhome pushes it towards it's limit with a fully loaded 26. Add a towd and it is over the limit and
anecdotally we see it shortens the life, though by how much is hard to quantify. It certainly still works, even a 5000 lbs towd isn't going to kill
the tranny immediately, but it will eventually. That eventually is unknown. However, the most important bit is that there is no other option. The
TH425 is the only transmission that works for our application.
--
Thanks,
Jeremy Knezek
1976 Glenbrook
Birmingham, AL

 

[john phillips]

I would think a 3.70 final drive would help it more than the higher engine
speed. Running in second to a higher speed may help but probably not. The
FD seems to be a weak point as well from what I have read. I have less than
500 miles on mine so everything is academic rather than real word
experience.
John Phillips
75 Avion VIN A26000
Retired
Rancho Cordova, CA 95670

On Fri, Apr 26, 2019 at 2:02 PM Jeremy via Gmclist
wrote:

> It's a robust transmission though the motorhome pushes it towards it's
> limit with a fully loaded 26. Add a towd and it is over the limit and
> anecdotally we see it shortens the life, though by how much is hard to
> quantify. It certainly still works, even a 5000 lbs towd isn't going to kill
> the tranny immediately, but it will eventually. That eventually is
> unknown. However, the most important bit is that there is no other option.
> The
> TH425 is the only transmission that works for our application.
> --
> Thanks,
> Jeremy Knezek
> 1976 Glenbrook
> Birmingham, AL
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*

 

[Jim Hupy]

I have 3:70 final drive gears. I installed them in August of 2011. I have
crossed Canada and back, as well as crossed the United States and retraced
Route 66 since then. Also, several trips North and South from Oregon to
Central California, and several trips to Canada and back. Normal speed for
me is 60 - 70+ MPH. Sometimes towing a box trailer. Drive it like I stole
it. The final drives are as reliable as an anvil. Don't worry about their
reliability. Or the engines. If they are in good shape, they work well for
a very long time.
Jim Hupy
Salem, Or

On Fri, Apr 26, 2019, 3:23 PM John Phillips via Gmclist <

> I would think a 3.70 final drive would help it more than the higher engine
> speed. Running in second to a higher speed may help but probably not. The
> FD seems to be a weak point as well from what I have read. I have less than
> 500 miles on mine so everything is academic rather than real word
> experience.
> John Phillips
> 75 Avion VIN A26000
> Retired
> Rancho Cordova, CA 95670
>
> On Fri, Apr 26, 2019 at 2:02 PM Jeremy via Gmclist <
> gmclist>

>
> > It's a robust transmission though the motorhome pushes it towards it's
> > limit with a fully loaded 26. Add a towd and it is over the limit and
> > anecdotally we see it shortens the life, though by how much is hard to
> > quantify. It certainly still works, even a 5000 lbs towd isn't going to
> kill
> > the tranny immediately, but it will eventually. That eventually is
> > unknown. However, the most important bit is that there is no other
> option.
> > The
> > TH425 is the only transmission that works for our application.
> > --
> > Thanks,
> > Jeremy Knezek
> > 1976 Glenbrook
> > Birmingham, AL
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
>
>
> --
>
> *John Phillips*
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[jim kanomata1]

With a 3.70 your only turning 450 rpm more and not lugging the engine.
Even on small hills, it makes lot of difference.
Life of the transmission is definitely lengthened

On Fri, Apr 26, 2019 at 2:12 PM John Phillips via Gmclist <

> I would think a 3.70 final drive would help it more than the higher engine
> speed. Running in second to a higher speed may help but probably not. The
> FD seems to be a weak point as well from what I have read. I have less than
> 500 miles on mine so everything is academic rather than real word
> experience.
> John Phillips
> 75 Avion VIN A26000
> Retired
> Rancho Cordova, CA 95670
>
> On Fri, Apr 26, 2019 at 2:02 PM Jeremy via Gmclist <
> gmclist>

>
> > It's a robust transmission though the motorhome pushes it towards it's
> > limit with a fully loaded 26. Add a towd and it is over the limit and
> > anecdotally we see it shortens the life, though by how much is hard to
> > quantify. It certainly still works, even a 5000 lbs towd isn't going to
> kill
> > the tranny immediately, but it will eventually. That eventually is
> > unknown. However, the most important bit is that there is no other
> option.
> > The
> > TH425 is the only transmission that works for our application.
> > --
> > Thanks,
> > Jeremy Knezek
> > 1976 Glenbrook
> > Birmingham, AL
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
>
>
> --
>
> *John Phillips*
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[kingsley coach]

" reliable as an anvil " it's been a while since I've heard that one..lol

Mike in NS

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On Fri, Apr 26, 2019 at 10:19 PM James Hupy via Gmclist <

> I have 3:70 final drive gears. I installed them in August of 2011. I have
> crossed Canada and back, as well as crossed the United States and retraced
> Route 66 since then. Also, several trips North and South from Oregon to
> Central California, and several trips to Canada and back. Normal speed for
> me is 60 - 70+ MPH. Sometimes towing a box trailer. Drive it like I stole
> it. The final drives are as reliable as an anvil. Don't worry about their
> reliability. Or the engines. If they are in good shape, they work well for
> a very long time.
> Jim Hupy
> Salem, Or
>
> On Fri, Apr 26, 2019, 3:23 PM John Phillips via Gmclist <

>
> > I would think a 3.70 final drive would help it more than the higher
> engine
> > speed. Running in second to a higher speed may help but probably not. The
> > FD seems to be a weak point as well from what I have read. I have less
> than
> > 500 miles on mine so everything is academic rather than real word
> > experience.
> > John Phillips
> > 75 Avion VIN A26000
> > Retired
> > Rancho Cordova, CA 95670
> >
> > On Fri, Apr 26, 2019 at 2:02 PM Jeremy via Gmclist <
> > gmclist>

> >
> > > It's a robust transmission though the motorhome pushes it towards it's
> > > limit with a fully loaded 26. Add a towd and it is over the limit and
> > > anecdotally we see it shortens the life, though by how much is hard to
> > > quantify. It certainly still works, even a 5000 lbs towd isn't going to
> > kill
> > > the tranny immediately, but it will eventually. That eventually is
> > > unknown. However, the most important bit is that there is no other
> > option.
> > > The
> > > TH425 is the only transmission that works for our application.
> > > --
> > > Thanks,
> > > Jeremy Knezek
> > > 1976 Glenbrook
> > > Birmingham, AL
> > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >
> >
> >
> > --
> >
> > *John Phillips*
> > _______________________________________________
> > 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
>

--
Michael Beaton
1977 Kingsley 26-11
1977 Eleganza II 26-3
Antigonish, NS

Life is too short to hold a grudge; slash some tires and call it even !

 

[Matt Colie]

> I would think a 3.70 final drive would help it more than the higher engine speed. Running in second to a higher speed may help but probably not.
> The FD seems to be a weak point as well from what I have read. I have less than 500 miles on mine so everything is academic rather than real word
> experience.
> John Phillips

Where's my crate? Ok, I have something to stand on.....

Here he is again, the refugee from the Detroit testing labs.
I have to put up a small argument to the above.
The final drive is not the "weak link", it is just the wrong part. From my experience, that final drive is as robust as the rest of the driveline.
It was wrong in the first 26 built, it is still wrong today. In my very light 23, it is still wrong, just not so much. I would still like to go to a
3.55, but today I have other issues with my coach. (If you didn't hear, big issues.)

James Hupy put it real right, if you are at running, and you open the throttle a little and it does not cause an immediate change in speed, you are
lugging. Technically, that means that you are in the wrong place on the engine's torque curve. Jim was also right when he said the RPM is free.

There is another very true point that automatic transmissions (as true today as it was then) do not like torque. Again here, RPM is free.

The engine in our coach was "rebuilt" (know what was done but I don't know why) at about 90K. That means it had about 80K on it when a piston broke.
Up until then, it was using about a quart of lube oil every 2K. When I tore it down and inspected it, there were two things that were very clear:
First was that if it had not broke #7 piston, it would have gone at least another 80K before the rings went bad. That would have cause a lube oil
consumption issue and not stopped the engine from producing close to full horsepower.
Second was that the rebuild was probably done by a "Production" rebuilder. This was a mistake. They punched to 30over (no rebore left) and ground
the crank to 30under (no regrind left). This is why you should be careful who does your rebuild.

I concur with those that say that the Oldsmobile engines were a great choice. There may be a few better engines built today, but engines this robust
are still not the common fare.

Someone asked what the common mode failure of these engines is, and I have been wondering that myself for the last fourteen years. As once and
industry professional, this is a particular interest and I have not seen one. We have been effectively informed of a number of engine failures. I
have not identified a leading cause. We have counted some piston failures that were probably casting failures. Most piston failures are the result
of running with knock. This can damage pistons pretty fast. More than a few spun bearings, but in a properly assembled and maintained engine, this
is just not a common issue. (If you have any doubt about your engine, check the lube oil level at every fuel stop and as a part of the morning walk
around (never skip the walk around) and any other time you happen think of it.) While lubrication failures do seem to top the list, these are most
common on a recently re-started engines. This is a good reason to both keep using your coach and to run a full synthetic oil. Lube oil oxidizes, and
synthetics are less prone to this. I do run M1 15-50 but that is because it did so well in some tests that the results were hard to ignore.

OK, that is the end of today's rant. I have to get other things done so I can get back to the things I really want to do.

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

 

[john shutzbaugh]

In my experience, reliability of early powertrains was outstanding. Bought our 77 455 Eleganza new in April of 78. In March of 93 at 172000 miles
Roland Wilbur & I replaced the engine with one he got rebuilt in Eugene Oregon. At the same time we put in a NEW transmission/final drive I got in
1980 when GM sold off all the leftovers. The original engine/transmission/final drive were still running great when removed, I just decided to get
them before they got me!

The replacement engine is still running strong at 243000 miles (71000 on engine #2), but the transmission is a different story. The NEW transmission
had the modulator fail on the test drive, and it later started slipping badly at about 5000 miles in. Maybe sitting for 13 years was not good for it,
even though we changed the fluid before installation. The local rebuild did OK until Manny rebuilt it and installed the PowerDrive chain. That
transmission now has about about 20000 on it & I really like that Ratio.

I did the GMC recommended service to the coach, except for using Amsoil synthetic & changing the oil yearly. Both engines use about a quart in 1200
miles. The rebuild did not pull any better than the hi-miler and I sometimes wondered why I pulled out a perfectly good engine, but realized it could
not run forever!

John Shutzbaugh
--
John Shutzbaugh, Vacaville, CA, ncserv;
77 Eleganza, bought it new, can't blame PO, and
78 Buskirk stretch, "What were we thinking?"