Home » Public Forums » GMCnet » [GMCnet] Grille to Radiator Duct
| [GMCnet] Grille to Radiator Duct [message #175968] |
Sat, 07 July 2012 22:31  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Today I finally completed the project I've worked on for the past 3 days:
The planned-for-years duct between the grille and the radiator of the GMC.
When I first saw a GMC I was surprised by the absence of any baffles to
route grille-admitted air through the radiator, and to prevent back-flow of
engine compartment air through the radiator. That was especially
surprising to me because of the emphasis Chevrolet places on the top in
their P-30 Chassis Owners' Manual.
Several years ago I installed Frank Jenkins' heavy rubberized fabric side
panels, similar to those on '77 & '78 GMC's, but I've only now gotten
around to completing the work I thought the factory should have done. The
propensity of the Cad500 engine to run at higher temperature than the Olds
finally convinced me to get busy.
I wanted to make the new duct from 10g diamond plate aluminum, like the
enclosure for my new HVAC. But the price of that material has increased
dramatically ove the past few months -- to something like $175 per 4'x8'
sheet. My metal working shop buddy didn't have large enough scraps and I
wouldn't agree to cut a full sheet. So, I used some tractor trailer mud
flaps I've had hanging on the wall for years. The material is some pliable
plastic almost 3/16" thick. Hopefully, with the short spans, and aluminum
edging, it will not sag excessively. If it does, I'll reinforce more; or,
resort to the AL.
Photos are at
http://www.gmcmhphotos.com/photos/g6117-grille-to-radiator-duct.html
or
http://goo.gl/5XojJ
Test results will follow next week.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #175982 is a reply to message #175968] |
Sun, 08 July 2012 03:00  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
| Ken Henderson wrote on Sat, 07 July 2012 22:31 |
So, I used some tractor trailer mud
flaps I've had hanging on the wall for years. The material is some pliable
plastic almost 3/16" thick. Hopefully, with the short spans, and aluminum
edging, it will not sag excessively. If it does, I'll reinforce more; or,
resort to the AL.
Photos are at
http://www.gmcmhphotos.com/photos/g6117-grille-to-radiator-duct.html
or
http://goo.gl/5XojJ
Test results will follow next week.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
|
On the way back from your farm after the Dothan rally a few years back, I found a large mud flap in the road that had fallen off of a semi trailer. This is the flap that goes in the middle between the two regular ones behind the wheels. You some times see them on gravel trucks. If this what you have, it is really heavy. You might have to do a weight and balance on the coach after you install it.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #175996 is a reply to message #175983] |
Sun, 08 July 2012 07:58 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Peter,
I've never done anything to protect the MC from rain. BUT, that rust is
not because of that oversight: It's probably never experienced rainwater
because I can't remember the last time I drove in rain and the GMC is
stored under cover. It's our ambient humidity that does the number on
exposed metal. I rust-proofed the previous MC, but the benefit didn't seem
worth the effort this time. :-)
The radiator duct didn't receive any rain consideration. The geometry of
the coach means requires some slope from the grille down to the top of the
radiator so that's fixed. Laterally, I could have only put about a 1/4"
crown down the middle, which wouldn't have helped enough to be worthwhile.
The water will just have to look out for itself and find its own route out
of there. At least the plastic panels won't rust!
Ken H.
On Sun, Jul 8, 2012 at 4:12 AM, Peter Bailey wrote:
> Ken,
> What have you done to run the rain that obviosly enters through your
> engine hatches judging by the rust on your master cylinder?
> Is your covers attached with angles for the water to drain forward or to
> the middle and forward?
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #176051 is a reply to message #176034] |
Sun, 08 July 2012 14:04 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
|
Senior Member |
|
|
Ken, Great, now I have to go look for the material. You can provide a cheap cover for the MC (at least the OEM) by using a 1/2 quart plastic milk bottle, just trim to fit by removing the top and one side. Slides on and costs almost nothing. STole this idea from a guy at International.
See you in Tennessee.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
|
|
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #176059 is a reply to message #176034] |
Sun, 08 July 2012 15:07 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Roy,
I made no changes outside of the side baffles (other than moving the AC
receiver dryer outside), so battery (all 3 under the passenger) maintenance
is unchanged, and I never had an air compressor up front.
Battery removal isn't even affected: Back when I could lift that much,
they could come straight out of the top just about as easily as through the
grille opening. For the past couple of years I've given up that technique
(actually, it abandoned me); now I use a pad on top of the arm of my
"cherry picker" to raise and lower the batteries through the wheel well.
Like this:
http://www.gmcmhphotos.com/photos/g5425-battery-lift.html
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
On Sun, Jul 8, 2012 at 12:34 PM, wrote:
>
>
> How do you access the battery and air pump?
> --
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #176060 is a reply to message #175968] |
Sun, 08 July 2012 15:15 |
 |
ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
|
Senior Member |
|
|
Ken,
Your documentation is terrific. I'm also happily surprised to see what a nice storage space is created with the top baffle in place. Perhaps this is the area where aluminum would be appropriate or perhaps coated steel to allow for magnetic hold-down catches, etc.
Could you elaborate about the mounting brackets at the radiator?
You've covered the top and sides but what about the bottom? Do you have an air dam there? Also, what do you do with the captured condensate from your air conditioning?
Larry Davick
A Mystery Machine
Sent from my iPad
On Jul 7, 2012, at 8:31 PM, Ken Henderson <hend4800@bellsouth.net> wrote:
> Today I finally completed the project I've worked on for the past 3 days:
> The planned-for-years duct between the grille and the radiator of the GMC.
>
> When I first saw a GMC I was surprised by the absence of any baffles to
> route grille-admitted air through the radiator, and to prevent back-flow of
> engine compartment air through the radiator. That was especially
> surprising to me because of the emphasis Chevrolet places on the top in
> their P-30 Chassis Owners' Manual.
>
> Several years ago I installed Frank Jenkins' heavy rubberized fabric side
> panels, similar to those on '77 & '78 GMC's, but I've only now gotten
> around to completing the work I thought the factory should have done. The
> propensity of the Cad500 engine to run at higher temperature than the Olds
> finally convinced me to get busy.
>
> I wanted to make the new duct from 10g diamond plate aluminum, like the
> enclosure for my new HVAC. But the price of that material has increased
> dramatically ove the past few months -- to something like $175 per 4'x8'
> sheet. My metal working shop buddy didn't have large enough scraps and I
> wouldn't agree to cut a full sheet. So, I used some tractor trailer mud
> flaps I've had hanging on the wall for years. The material is some pliable
> plastic almost 3/16" thick. Hopefully, with the short spans, and aluminum
> edging, it will not sag excessively. If it does, I'll reinforce more; or,
> resort to the AL.
>
> Photos are at
> http://www.gmcmhphotos.com/photos/g6117-grille-to-radiator-duct.html
> or
> http://goo.gl/5XojJ
>
> Test results will follow next week.
>
> Ken H.
> Americus, GA
> '76 X-Birchaven w/Cad500/Howell EFI+ & EBL
> www.gmcwipersetc.com
> ______________________________________________
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #176061 is a reply to message #176060] |
Sun, 08 July 2012 15:32 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Larry,
You're right: something stronger than my plastic would be better for
storage -- I didn't even consider that until it was all together and that
space magically appeared. I'll have to give it more thought. Magnetic
sounds good; rust doesn't. Since the front attachment is intentionally
light friction, I'll never consider very heavy cargo there.
At the sides of the radiator, the baffles are bolted to long U-brackets on
which the legs are attached with the AC evaporator's rubber isolators'
bolts -- I think those came with Frank Jenkins' side baffles. Not much
structure nor strength there -- nor needed.
At the top of the radiator, I used self-drilling & tapping screws, about
every 6", to attach a 36" long piece of 3/4"x3/4" aluminum angle, flange
up. After the top panels were completed and in place, I marked the
aluminum where the panels joined and cut it there. Then pop riveted the
panels to the bottom flange. So each panel can be removed individually by
removing it's horizontal screws there, the 2 vertical ones at the ends, and
those in the splice between the top panels.
The bottom was already taken care of by this:
http://www.gmcmhphotos.com/photos/g5632-under-bumper-air-scoop-amp-rock-guard.html
or
http://goo.gl/pStcD
Today's our 53rd anniversary, so SHE doesn't want me out working on/test
driving the GMC ("...I'd want to get through with it eventually...").
Ken H.
On Sun, Jul 8, 2012 at 4:15 PM, Larry Davick wrote:
> Ken,
>
> Your documentation is terrific. I'm also happily surprised to see what a
> nice storage space is created with the top baffle in place. Perhaps this is
> the area where aluminum would be appropriate or perhaps coated steel to
> allow for magnetic hold-down catches, etc.
>
> Could you elaborate about the mounting brackets at the radiator?
>
> You've covered the top and sides but what about the bottom? Do you have
> an air dam there? Also, what do you do with the captured condensate from
> your air conditioning?
>
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #176106 is a reply to message #175968] |
Sun, 08 July 2012 22:25 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
After running 6 hours in the 100+ degree heat I was contemplating doing this as well. Fan was engaged about 30% of the time at 65 MPH. On the return trip it was about 85 out and never came on except when I first slowed down (as it should). HOWEVER... I am going to think about this futher because GM didn't do it for a reason. I think this is because it is
1 Blocking fresh air from the heater box / AC fan inlet (at least it looks that way in the pictures)
2 Blocking cooling air from the engine bay and especially the exhaust manifolds. (Remember the Fiero where they added the "bilge blower" due to fires)
What made me think of this is on my 84 Riviera there is a plastic duct in in the chin spoiler to duct cooling air at the final drive. If that needs cooling from long term highspeed driving, so does other stuff.
I think I'm going to first concenterate on the chin type scoop to get air up and into the radiator as GM did on the 3rd gen F cars as the Firebird had no open grill at all, but high speed cooling was OK. But I'll be sure it doesn't block flow to the FD area.
I know on the G Regals if you don't have that air dam at the bottom of the core support it overheats. I also helps separate hot and cold and prevent regen of hot air. I think this is the main thing the GMC needs IMHO.
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #176112 is a reply to message #176061] |
Mon, 09 July 2012 00:06 |
|
ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
|
Senior Member |
|
|
53 years? My uncle would say - what a sentence!
Me, I'm thinking you are two lucky people.
Larry Davick
Sent from my iPad
On Jul 8, 2012, at 1:32 PM, Ken Henderson <hend4800@bellsouth.net> wrote:
> Larry,
>
> You're right: something stronger than my plastic would be better for
> storage -- I didn't even consider that until it was all together and that
> space magically appeared. I'll have to give it more thought. Magnetic
> sounds good; rust doesn't. Since the front attachment is intentionally
> light friction, I'll never consider very heavy cargo there.
>
> At the sides of the radiator, the baffles are bolted to long U-brackets on
> which the legs are attached with the AC evaporator's rubber isolators'
> bolts -- I think those came with Frank Jenkins' side baffles. Not much
> structure nor strength there -- nor needed.
>
> At the top of the radiator, I used self-drilling & tapping screws, about
> every 6", to attach a 36" long piece of 3/4"x3/4" aluminum angle, flange
> up. After the top panels were completed and in place, I marked the
> aluminum where the panels joined and cut it there. Then pop riveted the
> panels to the bottom flange. So each panel can be removed individually by
> removing it's horizontal screws there, the 2 vertical ones at the ends, and
> those in the splice between the top panels.
>
> The bottom was already taken care of by this:
> http://www.gmcmhphotos.com/photos/g5632-under-bumper-air-scoop-amp-rock-guard.html
> or
> http://goo.gl/pStcD
>
> Today's our 53rd anniversary, so SHE doesn't want me out working on/test
> driving the GMC ("...I'd want to get through with it eventually...").
>
> Ken H.
>
>
> On Sun, Jul 8, 2012 at 4:15 PM, Larry Davick wrote:
>
>> Ken,
>>
>> Your documentation is terrific. I'm also happily surprised to see what a
>> nice storage space is created with the top baffle in place. Perhaps this is
>> the area where aluminum would be appropriate or perhaps coated steel to
>> allow for magnetic hold-down catches, etc.
>>
>> Could you elaborate about the mounting brackets at the radiator?
>>
>> You've covered the top and sides but what about the bottom? Do you have
>> an air dam there? Also, what do you do with the captured condensate from
>> your air conditioning?
>>
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #176117 is a reply to message #176106] |
Mon, 09 July 2012 06:14 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
John,
I sort of share your concern about the exhaust manifolds -- I'll be
watching the wheel well liners carefully. That concern is partially
ameliorated by the fact that GMC did eventually install the side panels,
and I've had them for several years. If there's any sign of overheating
the liners, I'll try leaving the inner halves of them out (remember I split
them longitudinally many years ago).
The HVAC inlet I can't think of as a potential problem; it never received
ram air anyway, but I long ago blocked it and then eliminated it.
Frankly, I hadn't considered the final drive, it being down there about as
exposed as anything can get -- but my lower scoop could conceivably disrupt
the flow. And the FD does run hotter than most would probably guess. My
temperature gauge eventually shows it reaching 10-20*F below the engine.
I'll take a closer look at the potential obstruction.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
On Sun, Jul 8, 2012 at 11:25 PM, John R. Lebetski wrote:
>
>
> After running 6 hours in the 100+ degree heat I was contemplating doing
> this as well. Fan was engaged about 30% of the time at 65 MPH. On the
> return trip it was about 85 out and never came on except when I first
> slowed down (as it should). HOWEVER... I am going to think about this
> futher because GM didn't do it for a reason. I think this is because it is
> 1 Blocking fresh air from the heater box / AC fan inlet (at least it looks
> that way in the pictures)
> 2 Blocking cooling air from the engine bay and especially the exhaust
> manifolds. (Remember the Fiero where they added the "bilge blower" due to
> fires)
> What made me think of this is on my 84 Riviera there is a plastic duct in
> in the chin spoiler to duct cooling air at the final drive. If that needs
> cooling from long term highspeed driving, so does other stuff.
> I think I'm going to first concenterate on the chin type scoop to get air
> up and into the radiator as GM did on the 3rd gen F cars as the Firebird
> had no open grill at all, but high speed cooling was OK. But I'll be sure
> it doesn't block flow to the FD area.
> I know on the G Regals if you don't have that air dam at the bottom of the
> core support it overheats. I also helps separate hot and cold and prevent
> regen of hot air. I think this is the main thing the GMC needs IMHO.
> --
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #176119 is a reply to message #175968] |
Mon, 09 July 2012 06:41 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
|
Senior Member |
|
|
NICE WORK Ken!!. FWIW, about a year ago I did almost the exact same thing to my coach which also has the Cad 500 . I did it because the Cad has a tendency to run hotter than the Olds,,,or so they say. Before the duct, at highway speeds with temps above 80*, the fan clutch would come on quite often. Temps would climb slowly to 205 or so, fan would come on and drag the temp quickly down to 192 and shut off. I installed the duct. My first "hot" run was going to Goshen through Chicago in ambient temps well into the 90's. The only time the fan came on was when I slowed way down in heavy traffic or for small towns. Temps ran in the low 190's.
I used farm conveyer belt material around the two sides and top. For the bottom, I zip tied the stock rubber piece to the AC condensor to keep air from escaping there. The only screen I have in front of the radiator is in front to the lower part to keep road debris off of the radiator. I have had no troubles with excessive heat around the exhaust manifolds. JWID
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
|
|
|
|
| Re: [GMCnet] Grille to Radiator Duct [message #176120 is a reply to message #176119] |
Mon, 09 July 2012 06:49 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Sounds good, Larry; that's the sort of results I'm hoping for. While the
current 4208 fan clutch seems to have eliminated the roar, after I've tried
this arrangement for a while, I plan to re-install the HD clutch to see how
it works with the duct. It would be nice to know that lurking in the
background, never used, is the "big gun".
Ken H.
On Mon, Jul 9, 2012 at 7:41 AM, Larry wrote:
>
>
> NICE WORK Ken!!. FWIW, about a year ago I did almost the exact same thing
> to my coach which also has the Cad 500 . I did it because the Cad has a
> tendency to run hotter than the Olds,,,or so they say. Before the duct, at
> highway speeds with temps above 80*, the fan clutch would come on quite
> often. Temps would climb slowly to 205 or so, fan would come on and drag
> the temp quickly down to 192 and shut off. I installed the duct. My first
> "hot" run was going to Goshen through Chicago in ambient temps well into
> the 90's. The only time the fan came on was when I slowed way down in
> heavy traffic or for small towns. Temps ran in the low 190's.
>
> I used farm conveyer belt material around the two sides and top. For the
> bottom, I zip tied the stock rubber piece to the AC condensor to keep air
> from escaping there. The only screen I have in front of the radiator is in
> front to the lower part to keep road debris off of the radiator. I have
> had no troubles with excessive heat around the exhaust manifolds. JWID
> --
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
Goto Forum:
Current Time: Tue Oct 08 17:29:58 CDT 2024
Total time taken to generate the page: 0.01421 seconds
|
GMCforum
Search
Help
Register
Login
Home
