Tips for installing engine vents.

B

Bob Dunahugh

New member
Sep 17, 2012
2,784
4
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Scott. I see very little value due to location, and small size. Data can be had simple. Some ribbons taped to the vents. Then have someone in the passenger seat take some temps around that area while driving. If the ribbons stand out from the vents. Then you have good air flow. If the ribbons just flutter next to the body. You have ZIP for air flow.
To me. That money on the vents. Would be better spent on a fan shroud. Like the one GM installed on all 403 equipped GMCs. I should be quiet on this. But the GMC that I just got for our daughter has them. Never knew how small the hole is.
I pull a 24 ft enclosed trailer. With a shop/car in it. My GVW comes in at around 24,000 lbs. ( It's been to some GMCMI events that way. ) With a 403 that's bone stock as to cooling. It never gets over heated. Even in Lake Havasue City Az. In July at 114 degrees. With the A/C on high.
Bob Dunahugh
78 Royale since 2003
4 COPO Yenkos
 
What Bob said. I was having cooling issues only while underway at higher
speeds. Adding some vertical plywood baffles behind the grill to direct the
airflow through the radiator instead of around fixed the issue entirely.
And I had the fan shroud already.

sully
bellevue wa

> Scott. I see very little value due to location, and small size. Data can
> be had simple. Some ribbons taped to the vents. Then have someone in the
> passenger seat take some temps around that area while driving. If the
> ribbons stand out from the vents. Then you have good air flow. If the
> ribbons just flutter next to the body. You have ZIP for air flow.
> To me. That money on the vents. Would be better spent on a fan shroud.
> Like the one GM installed on all 403 equipped GMCs. I should be quiet on
> this. But the GMC that I just got for our daughter has them. Never knew how
> small the hole is.
> I pull a 24 ft enclosed trailer. With a shop/car in it. My GVW comes in
> at around 24,000 lbs. ( It's been to some GMCMI events that way. ) With a
> 403 that's bone stock as to cooling. It never gets over heated. Even in
> Lake Havasue City Az. In July at 114 degrees. With the A/C on high.
> Bob Dunahugh
> 78 Royale since 2003
> 4 COPO Yenkos
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
there are two stock baffles on either side of the radiator made out of some
kind of fiberboard material that direct ram air into the radiator

> What Bob said. I was having cooling issues only while underway at higher
> speeds. Adding some vertical plywood baffles behind the grill to direct the
> airflow through the radiator instead of around fixed the issue entirely.
> And I had the fan shroud already.
>
> sully
> bellevue wa
>
> On Sun, Jun 13, 2021 at 11:54 PM Bob Dunahugh

>
> > Scott. I see very little value due to location, and small size. Data can
> > be had simple. Some ribbons taped to the vents. Then have someone in the
> > passenger seat take some temps around that area while driving. If the
> > ribbons stand out from the vents. Then you have good air flow. If the
> > ribbons just flutter next to the body. You have ZIP for air flow.
> > To me. That money on the vents. Would be better spent on a fan
> shroud.
> > Like the one GM installed on all 403 equipped GMCs. I should be quiet on
> > this. But the GMC that I just got for our daughter has them. Never knew
> how
> > small the hole is.
> > I pull a 24 ft enclosed trailer. With a shop/car in it. My GVW comes
> in
> > at around 24,000 lbs. ( It's been to some GMCMI events that way. ) With a
> > 403 that's bone stock as to cooling. It never gets over heated. Even in
> > Lake Havasue City Az. In July at 114 degrees. With the A/C on high.
> > Bob Dunahugh
> > 78 Royale since 2003
> > 4 COPO Yenkos
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
Len,

Yes, unless someone has removed them or they have deteriorated over the
last 40 years. There was no sign of them on The War Pig when I purchased it.

Sully
bellevue wa

> there are two stock baffles on either side of the radiator made out of some
> kind of fiberboard material that direct ram air into the radiator
>

>
> > What Bob said. I was having cooling issues only while underway at higher
> > speeds. Adding some vertical plywood baffles behind the grill to direct
> the
> > airflow through the radiator instead of around fixed the issue entirely.
> > And I had the fan shroud already.
> >
> > sully
> > bellevue wa
> >
> > On Sun, Jun 13, 2021 at 11:54 PM Bob Dunahugh

> >
> > > Scott. I see very little value due to location, and small size. Data
> can
> > > be had simple. Some ribbons taped to the vents. Then have someone in
> the
> > > passenger seat take some temps around that area while driving. If the
> > > ribbons stand out from the vents. Then you have good air flow. If the
> > > ribbons just flutter next to the body. You have ZIP for air flow.
> > > To me. That money on the vents. Would be better spent on a fan
> > shroud.
> > > Like the one GM installed on all 403 equipped GMCs. I should be quiet
> on
> > > this. But the GMC that I just got for our daughter has them. Never knew
> > how
> > > small the hole is.
> > > I pull a 24 ft enclosed trailer. With a shop/car in it. My GVW comes
> > in
> > > at around 24,000 lbs. ( It's been to some GMCMI events that way. )
> With a
> > > 403 that's bone stock as to cooling. It never gets over heated. Even in
> > > Lake Havasue City Az. In July at 114 degrees. With the A/C on high.
> > > Bob Dunahugh
> > > 78 Royale since 2003
> > > 4 COPO Yenkos
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
interesting....still there on my 78.....original fasters were sheet metal
screws, now converted to nots, washers and bolts

> Len,
>
> Yes, unless someone has removed them or they have deteriorated over the
> last 40 years. There was no sign of them on The War Pig when I purchased
> it.
>
> Sully
> bellevue wa
>

>
> > there are two stock baffles on either side of the radiator made out of
> some
> > kind of fiberboard material that direct ram air into the radiator
> >

> >
> > > What Bob said. I was having cooling issues only while underway at
> higher
> > > speeds. Adding some vertical plywood baffles behind the grill to direct
> > the
> > > airflow through the radiator instead of around fixed the issue
> entirely.
> > > And I had the fan shroud already.
> > >
> > > sully
> > > bellevue wa
> > >
> > > On Sun, Jun 13, 2021 at 11:54 PM Bob Dunahugh

> > >
> > > > Scott. I see very little value due to location, and small size. Data
> > can
> > > > be had simple. Some ribbons taped to the vents. Then have someone in
> > the
> > > > passenger seat take some temps around that area while driving. If the
> > > > ribbons stand out from the vents. Then you have good air flow. If
> the
> > > > ribbons just flutter next to the body. You have ZIP for air flow.
> > > > To me. That money on the vents. Would be better spent on a fan
> > > shroud.
> > > > Like the one GM installed on all 403 equipped GMCs. I should be quiet
> > on
> > > > this. But the GMC that I just got for our daughter has them. Never
> knew
> > > how
> > > > small the hole is.
> > > > I pull a 24 ft enclosed trailer. With a shop/car in it. My GVW
> comes
> > > in
> > > > at around 24,000 lbs. ( It's been to some GMCMI events that way. )
> > With a
> > > > 403 that's bone stock as to cooling. It never gets over heated. Even
> in
> > > > Lake Havasue City Az. In July at 114 degrees. With the A/C on high.
> > > > Bob Dunahugh
> > > > 78 Royale since 2003
> > > > 4 COPO Yenkos
> > > > _______________________________________________
> > > > GMCnet mailing list
> > > > Unsubscribe or Change List Options:
> > > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
The radiator baffles were not in all years. They seen to have arrived about the time that the engine mounted "horse collar" for the fan departed, but
that is just my impression and may be inaccurate or completely bull shit.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
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

>
> The radiator baffles were not in all years. They seen to have arrived about the time that the engine mounted "horse collar" for the fan departed, but
> that is just my impression and may be inaccurate or completely bull shit.
>
> Matt
> --
> Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Near DTW - Twixt A2 and Detroit
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
 
Just a followup on my grille-to-radiator duct: After 9 years in there, the
truck mudflap material is still standing up well. And the duct really does
its job: My engine temperature stays within a couple of degrees of the
thermostat ALL the time. And the duct has, indeed, proven to be a handy
storage location. There's usually a shallow and a deep cooking pan on
there filled with odds & ends, like spare brake fluid. It's useful space
with no other commitment. That duct is one of the most useful of the MANY
mods I've done to the X-Birchaven.

Ken H.

> 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
>

> >
> > The radiator baffles were not in all years. They seen to have arrived
> about the time that the engine mounted "horse collar" for the fan departed,
> but
> > that is just my impression and may be inaccurate or completely bull
> shit.
> >
> > Matt
> > --
> > Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL,
> GMCES
> > Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum
> Brakes with Applied Control Arms
> > SE Michigan - Near DTW - Twixt A2 and Detroit
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
Remember the McDonalds McDLT commercial? The burger came in a double clamshell that “kept the hot side hot and the cool side cool” then you
assembled the sandwich prior to eating. The shrouding helps with that. As does the add on under core support spoiler. I know my friend a GM mechanic
when trouble shooting overheat complaints would visually check if that flap piece was missing first thing. Oddly we did not get that baffle, but the
add in one was a big help on my coach.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Since I started, I might as well finish the cooling tale: Early on, I
replaced the "horse-collar" with the fiberglass shroud from Frank Jenkins.
That helps the fan to pull cool air through the full radiator. It also
potentially poses a problem (as learned by Detroit's engineers): At road
speeds, the under-hood airflow can be impeded by the spinning fan. So, I
equipped the full shroud with spring-loaded doors which open when there's
pressure in the shroud, but close if the fan's creating suction. I really
didn't see any performance difference after that mod, but they're still
there working, so I only look at them occasionally.

I just realized that I posted photos of that mod 10+ years ago (it makes
most sense viewed last-to-first):
http://www.gmcmhphotos.com/photos/g5567-radiator-shroud-modification.html

I also found photos of the other significant cooling mod I did; addition of
an under-bumper scoop to limit air escaping around the lower portion of the
radiator:
http://www.gmcmhphotos.com/photos/g5632-under-bumper-air-scoop-26amp-3b-rock-guard.html

When I first bought the GMC in '98, Jim Bounds drove it around the block to
check performance before beginning work on it. When we got back, there was
a stream of water squirting from the thrown-rock created hole in that lower
radiator. While a can of Bar's Stop-Leak cured that one permanently, the
grille on the above scoop is intended to minimize the chances of my
aluminum radiator being similarly damaged.

After all this, I should note that the ONLY cooling problem I've ever had
was after installing the Cad500: Climbing the notorious Monteagle mountain
east of Nashville, the temp gauge got up to 237*F. The first person I saw
at the destination GMCMI Convention was Gene Dotson, with one of their new
radiators. My greeting to him was, pointing, "That's MINE.". Never had a
cooling problem since.

Ken H.

On Thu, Jun 17, 2021 at 9:30 AM Ken Henderson
wrote:

> Just a followup on my grille-to-radiator duct: After 9 years in there,
> the truck mudflap material is still standing up well. And the duct really
> does its job: My engine temperature stays within a couple of degrees of
> the thermostat ALL the time. And the duct has, indeed, proven to be a
> handy storage location. There's usually a shallow and a deep cooking pan
> on there filled with odds & ends, like spare brake fluid. It's useful
> space with no other commitment. That duct is one of the most useful of the
> MANY mods I've done to the X-Birchaven.
>
> Ken H.
>

>
>> 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
>>

>> >
>> > The radiator baffles were not in all years. They seen to have arrived
>> about the time that the engine mounted "horse collar" for the fan departed,
>> but
>> > that is just my impression and may be inaccurate or completely bull
>> shit.
>> >
>> > Matt
>> > --
>> > Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL,
>> GMCES
>> > Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum
>> Brakes with Applied Control Arms
>> > SE Michigan - Near DTW - Twixt A2 and Detroit
>> > _______________________________________________
>> > GMCnet mailing list
>> > Unsubscribe or Change List Options:
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>>
>
 
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