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[GMCnet] You really want to improve engine cooling the most. [message #364780]

Thu, 17 June 2021 09:23

BobDunahugh

Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA

Karma: 11

Senior Member

You must go look/then copy what GM did. On any GMC that came with a 403. Mid 77, and all of 78. Plus, as Ken H said. Great added storage for fluids, and funnels. Back when I was a member of GMCMI. And showed up with my enclosed, 24 ft trailer. At the Spring, or Fall events. (Great club.)That trailer caught people's attention. Never had cooling issues with that load at 24,000 lbs. GVW.
About 20 years ago. If you had a 403. You'd get. Too bad that you have a 403. You need to get a 455 in there. Trailer or not. Then Jim K at Applied GMC came out with the 3:70. THAT was a game changer for both engines. That 3:70 also improve engine/trans cooling. Plus put the 403 into its happy power RPM power band.
Bob Dunahugh
78 Royale since 2003
4 COPO Yenkos
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[GMCnet] Re: You really want to improve engine cooling the most. [message #364781 is a reply to message #364780]

Thu, 17 June 2021 10:06

jimk

Messages: 6734
Registered: July 2006
Location: Belmont, CA

Karma: 9

Senior Member

Bob,
So many people are not aware of the torque curve and have not spent much
time trying to understand .
I for one am never afraid to confer with people that have knowledge and
experience in those area.

On Thu, Jun 17, 2021 at 7:23 AM Bob Dunahugh wrote:

> You must go look/then copy what GM did. On any GMC that came with a 403.
> Mid 77, and all of 78. Plus, as Ken H said. Great added storage for
> fluids, and funnels. Back when I was a member of GMCMI. And showed up with
> my enclosed, 24 ft trailer. At the Spring, or Fall events. (Great
> club.)That trailer caught people's attention. Never had cooling issues
> with that load at 24,000 lbs. GVW.
> About 20 years ago. If you had a 403. You'd get. Too bad that you
> have a 403. You need to get a 455 in there. Trailer or not. Then Jim K at
> Applied GMC came out with the 3:70. THAT was a game changer for both
> engines. That 3:70 also improve engine/trans cooling. Plus put the 403 into
> its happy power RPM power band.
> Bob Dunahugh
> 78 Royale since 2003
> 4 COPO Yenkos
> _______________________________________________
> 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
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502

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Re: [GMCnet] You really want to improve engine cooling the most. [message #364784 is a reply to message #364780]

Thu, 17 June 2021 10:45

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

ok lads newbie here, how much money and how much work to fit one of these to my 403

Larry

Larry - Victoria BC - 1977 ex-Palm Beach "Ol' Leaky" 40,000 miles, PO said everything working but forgot the word NOT. Atwood helium fridge, water heater & furnace. SS exhaust system, Onan, Iota Converter, R134A, New fuel lines & heat exchange hoses

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[GMCnet] Re: You really want to improve engine cooling the most. [message #364785 is a reply to message #364781]

Thu, 17 June 2021 10:35

James Hupy

Messages: 6806
Registered: May 2010

Karma: -62

Senior Member

Having a whole bunch of experience with similar engines, (455-vs.-403) and
recalling those experiences, I would have to state my preference for the
403. You put that sucker on the "sweet spot" of it's torque curve and it is
more than a match for a 455.
And yes, the 3:70 gear ratio in the final drive completes the
package, along with advancing the CAMSHAFT timing about 4°. Turns it into a
whole different critter. Wouldn't trade my 403 straight up for a 455. Your
opinion might vary.
Jim Hupy
Salem, Oregon

On Thu, Jun 17, 2021, 8:07 AM Jim Kanomata wrote:

> Bob,
> So many people are not aware of the torque curve and have not spent much
> time trying to understand .
> I for one am never afraid to confer with people that have knowledge and
> experience in those area.
>
> On Thu, Jun 17, 2021 at 7:23 AM Bob Dunahugh wrote:
>
>> You must go look/then copy what GM did. On any GMC that came with a 403.
>> Mid 77, and all of 78. Plus, as Ken H said. Great added storage for
>> fluids, and funnels. Back when I was a member of GMCMI. And showed up
> with
>> my enclosed, 24 ft trailer. At the Spring, or Fall events. (Great
>> club.)That trailer caught people's attention. Never had cooling issues
>> with that load at 24,000 lbs. GVW.
>> About 20 years ago. If you had a 403. You'd get. Too bad that you
>> have a 403. You need to get a 455 in there. Trailer or not. Then Jim K at
>> Applied GMC came out with the 3:70. THAT was a game changer for both
>> engines. That 3:70 also improve engine/trans cooling. Plus put the 403
> into
>> its happy power RPM power band.
>> Bob Dunahugh
>> 78 Royale since 2003
>> 4 COPO Yenkos
>> _______________________________________________
>> 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
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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[GMCnet] Re: You really want to improve engine cooling the most. [message #364786 is a reply to message #364784]

Thu, 17 June 2021 10:54

James Hupy

Messages: 6806
Registered: May 2010

Karma: -62

Senior Member

If you have access to an existing coach with the 403 ( late77 or 78), Then
you can just copy what is in there. Easiest Way, I would think.
Jim Hupy
Salem, Oregon

On Thu, Jun 17, 2021 at 8:46 AM wrote:

> ok lads newbie here, how much money and how much work to fit one of these
> to my 403
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the
> word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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Re: [GMCnet] You really want to improve engine cooling the most. [message #364787 is a reply to message #364780]

Thu, 17 June 2021 11:06

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

I have a 77 with a 403, not sure what you mean by "copy what's in there?"

Larry

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[GMCnet] Re: You really want to improve engine cooling the most. [message #364789 is a reply to message #364787]

Thu, 17 June 2021 11:47

powwerjon

Messages: 849
Registered: March 2013

Karma: -2

Senior Member

The front air baffles were on the 77 403 & later coaches. Number of albums on the photo site.

http://www.gmcmhphotos.com/photos/gmc-part-numbers/p63294-air-baffles.html
http://www.gmcmhphotos.com/photos/gmc-part-numbers/p63295-air-baffles.html

and Ken H Baffle setup

http://www.gmcmhphotos.com/photos/g6117-grille-to-radiator-duct.html
Look at all the pictures in this series and read the captions under the pictures.

Do not use plywood in the engine compartment. Use the materials suggested by Ken.

J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 29.5’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan
> On Jun 17, 2021, at 12:06 PM, twlldeen@gmail.com wrote:
>
> I have a 77 with a 403, not sure what you mean by "copy what's in there?"
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Re: [GMCnet] You really want to improve engine cooling the most. [message #364791 is a reply to message #364787]

Thu, 17 June 2021 12:28

lqqkatjon

Messages: 2324
Registered: October 2010
Location: St. Cloud, MN

Karma: 5

Senior Member

Jim was confused. He thought you asked about installing a 403 engine in place of a 455....

as for 3.7 final drive, applied lists them @ just under $2000.00 but add in a core, shipping and taxes, probably $2500.00

then you have to swap it out.... can be a fairly easy DIY, or who knows what a shop might charge.

Applied GMC is I believe the sole supplier of the 3.7 final drives.

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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[GMCnet] Re: You really want to improve engine cooling the most. [message #364794 is a reply to message #364780]

Thu, 17 June 2021 13:22

BobDunahugh

Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA

Karma: 11

Senior Member

RPMs help cooling. More trans fluid to the cooler, More engine coolant to the radiator.
All engines have what is sometimes known to as sweet spots in their RPM ranges. AKA. Peek area of the torque curve. That sweet spot is mostly determined by the cam profile. ( Shape. ) The 455's start at about 2700 RPMs I believe? Maybe lower. Not sure. I'm into 403s. The 403 seems to start at 2950 RPMs. These sweet spots generally occur in a 300 RPM span. Also determined by the cam. Peak HP/Torque also occur in this short range. And that is at full throttle only. Stock FD is 3:07. That's 3.07 turns of the engine. To 1 turn of the tire. There are 3:21,3:42, 3:55, 3:70, and 4:10 as options. 3:21,to 3:55 do help. But just not there. Why go half way? And doesn't get your engine into its most efficient operation RPMs. So, you can run a higher engine vacuum. That's where the higher gas milage is.
For some reason. There has been this fear of RPMs. With GMC owners. One of my road race Yenkos has an idle of 2200 RPM. Runs in the 7000 range. With stock GM crank/rods.
Bob Dunahugh
78 Royale since 2003
4 COPO Yenkos
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[GMCnet] Re: You really want to improve engine cooling the most. [message #364798 is a reply to message #364794]

Thu, 17 June 2021 13:40

jimk

Messages: 6734
Registered: July 2006
Location: Belmont, CA

Karma: 9

Senior Member

Remember, the core deposit is refundable charge.

On Thu, Jun 17, 2021 at 11:24 AM Bob Dunahugh wrote:

> RPMs help cooling. More trans fluid to the cooler, More engine coolant
> to the radiator.
> All engines have what is sometimes known to as sweet spots in their RPM
> ranges. AKA. Peek area of the torque curve. That sweet spot is mostly
> determined by the cam profile. ( Shape. ) The 455's start at about 2700
> RPMs I believe? Maybe lower. Not sure. I'm into 403s. The 403 seems to
> start at 2950 RPMs. These sweet spots generally occur in a 300 RPM span.
> Also determined by the cam. Peak HP/Torque also occur in this short range.
> And that is at full throttle only. Stock FD is 3:07. That's 3.07 turns of
> the engine. To 1 turn of the tire. There are 3:21,3:42, 3:55, 3:70, and
> 4:10 as options. 3:21,to 3:55 do help. But just not there. Why go half way?
> And doesn't get your engine into its most efficient operation RPMs. So, you
> can run a higher engine vacuum. That's where the higher gas milage is.
> For some reason. There has been this fear of RPMs. With GMC owners.
> One of my road race Yenkos has an idle of 2200 RPM. Runs in the 7000 range.
> With stock GM crank/rods.
> Bob Dunahugh
> 78 Royale since 2003
> 4 COPO Yenkos
> _______________________________________________
> 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
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:

Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502

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Re: [GMCnet] You really want to improve engine cooling the most. [message #364820 is a reply to message #364780]

Fri, 18 June 2021 10:25

boybach

Messages: 566
Registered: December 2020
Location: Vancouver Island

Karma: 4

Senior Member

Ok lads, I'll look in the archive/check out what's involved in swapping out the final drive.

Other than the delivery drive 3 months ago (600 km through the coastal range, B.C.) she's yet to make her maiden voyage as a freshly all fixed up coach. I'm planning on taking her up island next week or so, first part of the trip involves a steady climb of about 10 miles so I'll see how that goes. Of course on the delivery drive there were plenty of ups and downs too so not really a new experience. I do fancy a 3.7 though from what you guys are saying ...Maybe when the border opens up, I'll go to California and buy one for cash!

Larry

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[GMCnet] Re: You really want to improve engine cooling the most. [message #364821 is a reply to message #364820]

Fri, 18 June 2021 10:44

James Hupy

Messages: 6806
Registered: May 2010

Karma: -62

Senior Member

I had a newly installed 3:70 in my 403 equipped coach when we did a
Cross-Canada rolling rally led by Duane Jacobsen from White Rock, B.C.
He thought it might to be cool to take us to Whistler Resort via some
1st Nation goat trails. 18% uphill grade for 26 miles. 1st gear, foot to
the floor, 3600 RPM grind it out. Same deal on the other side, but
downhill. Sure glad I had that 3:70. Not sure if the 3:07 would have made
it. Best single improvement that I have done to my coach. Most noticeable
performance gain that you can do, hands down.
Jim Hupy
Salem, Oregon

On Fri, Jun 18, 2021, 8:28 AM wrote:

> Ok lads, I'll look in the archive/check out what's involved in swapping
> out the final drive.
>
> Other than the delivery drive 3 months ago (600 km through the coastal
> range, B.C.) she's yet to make her maiden voyage as a freshly all fixed up
> coach. I'm planning on taking her up island next week or so, first part of
> the trip involves a steady climb of about 10 miles so I'll see how that
> goes. Of course on the delivery drive there were plenty of ups and downs
> too so not really a new experience. I do fancy a 3.7 though from what you
> guys are saying ...Maybe when the border opens up, I'll go to California
> and buy one for cash!
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the
> word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
_______________________________________________
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Unsubscribe or Change List Options:

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