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

Bob Dunahugh

New member
Sep 17, 2012
2,784
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3
The hardest things on any engine are. Lost's of cold starts, short trips, and luging with too much throttle. Our GMC's have few cold starts as to miles driven. Not much for short trips. And get a 3:70 final drive. With standard 10W-30 oil/filter changes in the range of 3000 miles. Plastic timing gear changed out. Howell/GM EFI helps a lot. 200,000 shouldn't be a problem. I have the 403 that came out of our burned 78 GMC. Has never been apart except for the plastic cam gear replacement. Idle oil pressure hot is just under 30 PSI. Compression readings 140 to 145 PSI. ( New 150 to 155 PSI.) Used a qt of oil in 2500 miles. And has 154,000 miles on it. And I'm looking for another GMC to put that 403 in. Our present 78 Royale, 403, gets lots of oil changes. 3:70 FD, and a Howell/GM EFI. Bob Dunahugh
 
What RPM do you need to be above to not be lugging at full throttle?
John Phillips
75 Avion VIN A26000
Retired
Rancho Cordova, CA 95670

On Fri, Apr 26, 2019 at 12:15 PM Bob Dunahugh via Gmclist <

> The hardest things on any engine are. Lost's of cold starts, short
> trips, and luging with too much throttle. Our GMC's have few cold starts as
> to miles driven. Not much for short trips. And get a 3:70 final drive.
> With standard 10W-30 oil/filter changes in the range of 3000 miles.
> Plastic timing gear changed out. Howell/GM EFI helps a lot. 200,000
> shouldn't be a problem. I have the 403 that came out of our burned 78 GMC.
> Has never been apart except for the plastic cam gear replacement. Idle oil
> pressure hot is just under 30 PSI. Compression readings 140 to 145 PSI. (
> New 150 to 155 PSI.) Used a qt of oil in 2500 miles. And has 154,000 miles
> on it. And I'm looking for another GMC to put that 403 in. Our present 78
> Royale, 403, gets lots of oil changes. 3:70 FD, and a Howell/GM EFI. Bob
> Dunahugh
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*
 
If you can add more throttle, and the vehicle easily gains speed (rpm)
then, you more than likely are not lugging the engine. If you cannot gain
speed by pressing harder on the accelerator, you are more than likely
lugging the engine. Cure? Downshift into a lower gear.
Jim Hupy
Salem, Or

On Fri, Apr 26, 2019, 3:17 PM John Phillips via Gmclist <

> What RPM do you need to be above to not be lugging at full throttle?
> John Phillips
> 75 Avion VIN A26000
> Retired
> Rancho Cordova, CA 95670
>
> On Fri, Apr 26, 2019 at 12:15 PM Bob Dunahugh via Gmclist <

>
> > The hardest things on any engine are. Lost's of cold starts, short
> > trips, and luging with too much throttle. Our GMC's have few cold starts
> as
> > to miles driven. Not much for short trips. And get a 3:70 final drive.
> > With standard 10W-30 oil/filter changes in the range of 3000 miles.
> > Plastic timing gear changed out. Howell/GM EFI helps a lot. 200,000
> > shouldn't be a problem. I have the 403 that came out of our burned 78
> GMC.
> > Has never been apart except for the plastic cam gear replacement. Idle
> oil
> > pressure hot is just under 30 PSI. Compression readings 140 to 145 PSI. (
> > New 150 to 155 PSI.) Used a qt of oil in 2500 miles. And has 154,000
> miles
> > on it. And I'm looking for another GMC to put that 403 in. Our present
> 78
> > Royale, 403, gets lots of oil changes. 3:70 FD, and a Howell/GM EFI.
> Bob
> > Dunahugh
> > _______________________________________________
> > 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
>
 
My 425 trans/3:70 have been in service since 2003. In two different 78 Roy=
ales. I personally rebuilt it in that year. And now have 87,000 miles on =
the pair. We've gone on one trip in all those years without towing somethi=
ng. Thus my lowest GVW all that time. Comes in at 17,000 lbs. When I'm t=
owing my 24 ft trailer enclosed trailer. That has a shop/Yenko in it. My GV=
W comes in at just under 25,000 lbs. And all this with a 403. I don't use =
any synthetic oil/fluid/lubes. Never let the engine oil/filter go more the =
3,000 miles. Change trans fluid every year. FD, and power steering fluid ev=
ery other trans fluid change. I strongly believe that changing oil/fluids =
is the key to longevity. Over the use of synthetics. Oils CHEEP. Not rebuil=
ds. So if there's a GMC out there that gets REALLY loaded. I think that ou=
rs is at the top. I have one rule that I believe in. Never use more the ha=
lf throttle while pulling long steep grades. And DO NOT care how fast I'm g=
oing. Bob Dunahugh 78-403 Royale. ________________________________ =
From: Bob Dunahugh Sent: Friday, April 26, 2019 2:14 PM To: gmclist=
t.gmcnet.org Subject: RE: The Olds 403/455 were an outstanding choice for=
our GMC's The hardest things on any engine are. Lost's of cold star=
ts, short trips, and luging with too much throttle. Our GMC's have few cold=
starts as to miles driven. Not much for short trips. And get a 3:70 final =
drive. With standard 10W-30 oil/filter changes in the range of 3000 miles=
. Plastic timing gear changed out. Howell/GM EFI helps a lot. 200,000 shoul=
dn't be a problem. I have the 403 that came out of our burned 78 GMC. Has n=
ever been apart except for the plastic cam gear replacement. Idle oil press=
ure hot is just under 30 PSI. Compression readings 140 to 145 PSI. ( New 15=
0 to 155 PSI.) Used a qt of oil in 2500 miles. And has 154,000 miles on it.=
And I'm looking for another GMC to put that 403 in. Our present 78 Royale=
, 403, gets lots of oil changes. 3:70 FD, and a Howell/GM EFI. Bob Dunahu=
gh
 
Matt said it perfectly on the FD. Not a weak part. Just the wrong part. To =
me. Jim K's 3:70 FD is a great ratio. Towing or NOT. The 3:55 to 3:21 do he=
lp some. I see it that. If your spending the money. Why not get the most be=
nefit from that cash outlay. Want to take the most load off your trans. And=
have it run cooler? The 3:70/4:10 will do it. And the power drive does not=
hing beneficial for the trans. That's a fact. It just makes it easier to pu=
t more load on the trans. After installing the 3:70. Gas mileage went up d=
ue to running a higher intake vacuum. I'll get off my box now. ( Grin.) W=
ant to keep me off my box? Don't talk about drivetrain components. Bob D=
unahugh 78 Royale ________________________________ From: Bob Dunahu=
gh Sent: Saturday, April 27, 2019 1:16 AM To: gm=
clist Subject: The Olds 403/455 were an outstanding choic=
e for our GMC's My 425 trans/3:70 have been in service since 2003. In=
two different 78 Royales. I personally rebuilt it in that year. And now h=
ave 87,000 miles on the pair. We've gone on one trip in all those years w=
ithout towing something. Thus my lowest GVW all that time. Comes in at 1=
7,000 lbs. When I'm towing my 24 ft trailer enclosed trailer. That has a sh=
op/Yenko in it. My GVW comes in at just under 25,000 lbs. And all this with=
a 403. I don't use any synthetic oil/fluid/lubes. Never let the engine oi=
l/filter go more the 3,000 miles. Change trans fluid every year. FD, and po=
wer steering fluid every other trans fluid change. I strongly believe that=
changing oil/fluids is the key to longevity. Over the use of synthetics. O=
ils CHEEP. Not rebuilds. So if there's a GMC out there that gets REALLY lo=
aded. I think that ours is at the top. I have one rule that I believe in. =
Never use more the half throttle while pulling long steep grades. And DO NO=
T care how fast I'm going. Bob Dunahugh 78-403 Royale. ______________=
__________________ From: Bob Dunahugh Sent: Friday, April 26, 2019 2:14=
PM To: gmclist Subject: RE: The Olds 403/455 were an o=
utstanding choice for our GMC's The hardest things on any engine are.=
Lost's of cold starts, short trips, and luging with too much throttle. Ou=
r GMC's have few cold starts as to miles driven. Not much for short trips. =
And get a 3:70 final drive. With standard 10W-30 oil/filter changes in th=
e range of 3000 miles. Plastic timing gear changed out. Howell/GM EFI helps=
a lot. 200,000 shouldn't be a problem. I have the 403 that came out of our=
burned 78 GMC. Has never been apart except for the plastic cam gear replac=
ement. Idle oil pressure hot is just under 30 PSI. Compression readings 140=
to 145 PSI. ( New 150 to 155 PSI.) Used a qt of oil in 2500 miles. And has=
154,000 miles on it. And I'm looking for another GMC to put that 403 in. =
Our present 78 Royale, 403, gets lots of oil changes. 3:70 FD, and a Howe=
ll/GM EFI. Bob Dunahugh
 
Being as Dunahugh is the Guru, I'll gently hijack his thread - or Mike's. Anyhow, local guy wants to sell a '67 Corvair Monza and trailer. Standoff
repaint with some bubbles. Interior is in good condition and cleaned up. Automatic car. Engine looks shot - ignition components off, fan and shroud
and belt off alternator off carbs off, lotsa greasy dirt n stuff. But a new battery. I figure it's worth the trailer it's on, is there any money
magic in a run out mechanical basket case? Like a GMC, if you have room, save it for parts?

--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
 
We also have the Limited Slip Differential option.
We have been supplying them for few years ad have proven to be a great
option.
I have had many people call me and tell me how much they like what it does
for them.
Limited Slip is just what it says, The front wheels cannot be locked up but
allowed to slip a little when turning corners. So there is a built in
slipage

On Sat, Apr 27, 2019 at 9:44 AM Bob Dunahugh via Gmclist <

> Matt said it perfectly on the FD. Not a weak part. Just the wrong part. To
> me. Jim K's 3:70 FD is a great ratio. Towing or NOT. The 3:55 to 3:21 do
> help some. I see it that. If your spending the money. Why not get the most
> benefit from that cash outlay. Want to take the most load off your trans.
> And have it run cooler? The 3:70/4:10 will do it. And the power drive does
> nothing beneficial for the trans. That's a fact. It just makes it easier to
> put more load on the trans. After installing the 3:70. Gas mileage went up
> due to running a higher intake vacuum. I'll get off my box now. ( Grin.)
> Want to keep me off my box? Don't talk about drivetrain components. Bob
> Dunahugh 78 Royale
>
> ________________________________
> From: Bob Dunahugh
> Sent: Saturday, April 27, 2019 1:16 AM
> To: gmclist
> Subject: The Olds 403/455 were an outstanding choice for our GMC's
>
> My 425 trans/3:70 have been in service since 2003. In two different 78
> Royales. I personally rebuilt it in that year. And now have 87,000 miles
> on the pair. We've gone on one trip in all those years without towing
> something. Thus my lowest GVW all that time. Comes in at 17,000 lbs.
> When I'm towing my 24 ft trailer enclosed trailer. That has a shop/Yenko in
> it. My GVW comes in at just under 25,000 lbs. And all this with a 403. I
> don't use any synthetic oil/fluid/lubes. Never let the engine oil/filter go
> more the 3,000 miles. Change trans fluid every year. FD, and power steering
> fluid every other trans fluid change. I strongly believe that changing
> oil/fluids is the key to longevity. Over the use of synthetics. Oils CHEEP.
> Not rebuilds. So if there's a GMC out there that gets REALLY loaded. I
> think that ours is at the top. I have one rule that I believe in. Never
> use more the half throttle while pulling long steep grades. And DO NOT care
> how fast I'm going. Bob Dunahugh 78-403 Royale.
>
> ________________________________
> From: Bob Dunahugh
> Sent: Friday, April 26, 2019 2:14 PM
> To: gmclist
> Subject: RE: The Olds 403/455 were an outstanding choice for our GMC's
>
> The hardest things on any engine are. Lost's of cold starts, short
> trips, and luging with too much throttle. Our GMC's have few cold starts as
> to miles driven. Not much for short trips. And get a 3:70 final drive.
> With standard 10W-30 oil/filter changes in the range of 3000 miles.
> Plastic timing gear changed out. Howell/GM EFI helps a lot. 200,000
> shouldn't be a problem. I have the 403 that came out of our burned 78 GMC.
> Has never been apart except for the plastic cam gear replacement. Idle oil
> pressure hot is just under 30 PSI. Compression readings 140 to 145 PSI. (
> New 150 to 155 PSI.) Used a qt of oil in 2500 miles. And has 154,000 miles
> on it. And I'm looking for another GMC to put that 403 in. Our present 78
> Royale, 403, gets lots of oil changes. 3:70 FD, and a Howell/GM EFI. Bob
> Dunahugh
> _______________________________________________
> 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