Home » Public Forums » GMCnet » [GMCnet] Radiator Duct Test, etc
| [GMCnet] Radiator Duct Test, etc [message #176668] |
Fri, 13 July 2012 19:46  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Well, I finally got around to taking a couple of test rides with the
new radiator duct in place. It was about 95*F when I went for a 25
mile ride yesterday. The temperature didn't change much from my
earlier reported 196*F-202*F norm. In fact, it surprised me by
staying on 200*F most of the time. I'd expected a little drop but it
didn't happen. But the temperature did vary less. About the only
time it changed was when I stopped a couple of times and idled until
the temperature stabilized. For about 5 minutes, the temp would
slowly rise to 210*F, then stay there for another 5 minutes, when I
got tired of watching it and drove again. Then the temperature
dropped back to 200*F within 1/4 mile. A 15 mile ride today went just
the same.
It may be my imagination, but I seem to have less engine noise in the
cockpit. But I also THINK I have a wind noise that I didn't have
before. With my hearing (or lack thereof), it doesn't much matter.
Then, yesterday, I finally wrecked the HF 1/2" electric impact wrench.
I bought it 3-4 years, maybe more, ago, expecting it to last a year.
The blades needed changing on the ZTR mower. The 5/8" bolts holding
them would not budge. The Craftsman impact wrench didn't do ANY good.
The HF removed 2 of the 3, but the third, after 'way too much
hammering, caused the output shaft of the HF wrench to twist in two
inside the nose housing. I finally had to grip the pulley on the top
side and use a pull handle on the bolt to break it loose. Next stop:
HF for a new impact wrench.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Radiator Duct Test, etc [message #176669 is a reply to message #176668] |
Fri, 13 July 2012 19:54  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Senior Member |
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What do you make of that, Ken.
I don't recall what your thermostat temperature is rated at. Do you think your fan clutch kicking it at 210 and your thermostat at 200? I realize that the temperature at the thermostat may be different than the gauge, and the air temp at the clutch will vary from the gauge as well.
Just trying to make sense of this.
Larry Davick
Fremont, California
A Mystery Machine
'76 (ish) Palm Beach
----- Original Message -----
From: "Ken Henderson" <hend4800@bellsouth.net>
To: "gmclist" <gmclist@temp.gmcnet.org>
Sent: Friday, July 13, 2012 5:46:17 PM
Subject: [GMCnet] Radiator Duct Test, etc
Well, I finally got around to taking a couple of test rides with the
new radiator duct in place. It was about 95*F when I went for a 25
mile ride yesterday. The temperature didn't change much from my
earlier reported 196*F-202*F norm. In fact, it surprised me by
staying on 200*F most of the time. I'd expected a little drop but it
didn't happen. But the temperature did vary less. About the only
time it changed was when I stopped a couple of times and idled until
the temperature stabilized. For about 5 minutes, the temp would
slowly rise to 210*F, then stay there for another 5 minutes, when I
got tired of watching it and drove again. Then the temperature
dropped back to 200*F within 1/4 mile. A 15 mile ride today went just
the same.
It may be my imagination, but I seem to have less engine noise in the
cockpit. But I also THINK I have a wind noise that I didn't have
before. With my hearing (or lack thereof), it doesn't much matter.
Then, yesterday, I finally wrecked the HF 1/2" electric impact wrench.
I bought it 3-4 years, maybe more, ago, expecting it to last a year.
The blades needed changing on the ZTR mower. The 5/8" bolts holding
them would not budge. The Craftsman impact wrench didn't do ANY good.
The HF removed 2 of the 3, but the third, after 'way too much
hammering, caused the output shaft of the HF wrench to twist in two
inside the nose housing. I finally had to grip the pulley on the top
side and use a pull handle on the bolt to break it loose. Next stop:
HF for a new impact wrench.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
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GMCnet mailing list
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] Radiator Duct Test, etc [message #176675 is a reply to message #176669] |
Fri, 13 July 2012 21:26 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Larry,
The fan clutch never came on. I run the Cad-recommended 195*F
thermostat. I'm very pleased with this 200*F. I'd been convinced
before installing the first 500 that I'd see 220*F, and that was
conservative as it turned out. This engine seems very happy at 200*F.
The mystery to me is why the duct MAY have run the temperature up a
tad -- and I don't understand why the temperature seems more stable.
We'll see what happens next week when we embark on the 2000 mile trip
-- this time towing the CRV, which I haven't yet done.
Ken H.
On Fri, Jul 13, 2012 at 8:54 PM, Larry Davick wrote:
> What do you make of that, Ken.
>
> I don't recall what your thermostat temperature is rated at. Do you think your fan clutch kicking it at 210 and your thermostat at 200? I realize that the temperature at the thermostat may be different than the gauge, and the air temp at the clutch will vary from the gauge as well.
>
> Just trying to make sense of this.
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Radiator Duct Test, etc [message #176678 is a reply to message #176668] |
Fri, 13 July 2012 22:17 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I did some testing a few years ago with a multi input digital meter. I taped one probe to the thermostat neck and hung one between the radiator and fan. All stock 77. I won't go into all the details, but in short, the water temp stays very stable and the air temp swings all over the place depending on engine (pump) speed and air speed. All your findings seem to make sense, except that higher temp at idle. Mine runs coolest at idle even with the AC on. I proved this again in a traffic jam coming home from the U.P. last Sun. Road load drives my temp up and at idle it will never overheat in stop and go where most vehicles are the worst. The GMC seems to behave inversly due to it's weight I guess. I did look at mine again in the driveway and I'm reluctant to do the side panels as all that "wasted" air is going past the manifolds and I don't want the "dog locked in a hot car effect" keep us posted on the results of the trip.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Radiator Duct Test, etc [message #176710 is a reply to message #176678] |
Sat, 14 July 2012 13:58 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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I have made the same observation with The War Pig. At 2800 rpm at freeway speeds the temp stays fairly constant at just below 3/4 on stock gauge. When I slow to a crawl in hot highway conditions the temp drops dramatically to just below 1/2. Conventional thinking would be that the fan and shroud are functioning correctly as they have their greatest impact at idle. I too am curious about your ducting Ken. I have considered a very similar modification. I have a new high efficiency core brass/copper radiator, new hoses,water pump,fail safe thermostat from Jim k ,and factory shroud without the metal Venturi ring. I also have removed the wheel liners and my trans in plumbed only to an external cooler and not through the radiator. I wonder if the engine oil passing through the radiator is elevating the engine water temps under highway loads? It will be good to see the results of your testing Ken. If there are no cooling gains from the ducting I will look much harder at cooling the
oil with an aux oil cooler.
Sully
77 royale
Sent from my iPhone
On Jul 13, 2012, at 8:17 PM, John R. Lebetski <gransport@aol.com> wrote:
>
>
> I did some testing a few years ago with a multi input digital meter. I taped one probe to the thermostat neck and hung one between the radiator and fan. All stock 77. I won't go into all the details, but in short, the water temp stays very stable and the air temp swings all over the place depending on engine (pump) speed and air speed. All your findings seem to make sense, except that higher temp at idle. Mine runs coolest at idle even with the AC on. I proved this again in a traffic jam coming home from the U.P. last Sun. Road load drives my temp up and at idle it will never overheat in stop and go where most vehicles are the worst. The GMC seems to behave inversly due to it's weight I guess. I did look at mine again in the driveway and I'm reluctant to do the side panels as all that "wasted" air is going past the manifolds and I don't want the "dog locked in a hot car effect" keep us posted on the results of the trip.
> --
> John Lebetski
> Chicago, IL
> 77 Eleganza II
> Source America First
> _______________________________________________
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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