| Re: [GMCnet] Radiators [message #225340] |
Sat, 12 October 2013 11:44 |
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hnielsen2
Messages: 1434
Registered: February 2004
Location: Alpine CA
Karma: 0
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Senior Member |
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Same here never a cooling problem.
Keep it clean
We run our GMC all over the Southwest desert and mountains.
455 with cam from Jim B, roller rockers, Mondelo (sp?) push rods, roller timing chain, Paterson disturber , 3:70 final drive, Manny one ton front end.
Howard
Alpine Ca
Home is at 2,400'
All is well with my Lord
> On Oct 12, 2013, at 8:50, "Rob Mueller" <robmueller@iinet.net.au> wrote:
>
> Cameron,
>
> There is nothing wrong with the design of the GMC cooling system if all the components are working properly. Think about it for a
> moment there were 12,941 of these units built and if the cooling system was not designed properly owners would have been all over
> GMC!
>
> I've inserted some comments below in CAPS for clarity (not shouting), hope you don't get upset.
>
> Regards,
> Rob M.
>
> -----Original Message-----
> From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of cameron
>
> Interesting results
>
> I actually asked a engine building friend of mine and what he told me was that cooling systems are designed to cool the engine at
> 100% of its heating capacity running normally.
>
> THE COOLING SYSTEM IS DESIGNED TO HANDLE THE HEAT GENERATED BY THE ENGINE WHETHER IT IS IN NOME, ALASKA IN THE MIDDLE OF WINTER TO
> DEATH VALLEY IN THE MIDDLE OF SUMMER.
>
> So it would make sense that since the engines that we have in our rigs are not running normally but under a extra amount of load it
> would make scene that the cooling capacity of the existing cooling system would be insufficient to cool the engine.
>
> THE DRIVE DRAIN IN A GMC WAS LIFTED OUT OF THE TORONADO AND INSTALLED IN THE GMC - BUT THE RADIATOR SIZE WAS INCREASED TO HANDLE THE
> EXTRA HEAT LOAD THE ENGINE DEVELOPED MOVING A 12,500 VEHICLE.
>
> Also since I have rebuilt the engine to produce more HP etc then there will be more heat produced beyond that.
>
> LETS SAY IT TAKES 100 HP TO MOVE A GMC DOWN THE ROAD AT 60 MILES PER HOUR IF YOU HAVE AN ENGINE THAT PRODUCES TWICE AS MUCH HP AS
> THE STOCK ENGINE IT IS STILL ONLY GOING TO TAKE 100 HP TO MOVE YOUR GMC DOWN THE ROAD AT 60 MPH.
>
> This is actually proven since the aluminum radiators have a greater cooling capacity then the stock brass.
>
> YOU ARE CORRECT ALUMINUM TRANSFERS HEAT FASTER THAN BRASS.
>
> When I rebuilt my engine I had the radiator rodded and cleaned so I know it is cooling as best as it can.
>
> GET AN INFARED THERMOMETER FROM HARBOR FREIGHT AND WITH YOUR GMC AT OPERATING TEMP SHOOT THE RADIATOR IN AS MANY PLACES AS POSSIBLE
> TO SEE WHAT THE TEMP IS. IT IS QUITE POSSIBLE THAT WHEN YOU HAD YOUR RADIATOR REPAIRED THEY MAY HAVE BLOCKED PASSAGES THAT WERE
> LEAKING.
>
> So my conclusion would be that there are three significant defects in the cooling design.
>
> First there is too much of a high pressure air zone in the engine compartment, thus keeping the hot air swirling around the
> compartment. Even with the additional vents the air pressure is still too high in the engine compartment.
>
> AT SPEED THE AIR GOES IN THROUGHT THE GRILL PAST THE RADIATOR AROUND THE ENGINE, HITS THE REAR FIREWALL AND EXITS UNDER THE COACH. I
> DON'T UNDERSTAND WHAT WOULD MAKE IT "swirling around the compartment."
>
> Second the radiator does have a poor design for air flow as an intake. If you look at all of the newer designs for any radiator
> there is a high pressure zone in front of the radiator and low in the back. This is accomplished by the fan in the GMC but when the
> fan is free wheeling then there is little to no pressure that is created. The ducting work that some others have done look like
> they would solve this problem.
>
> THERE IS A HIGH PRESSURE ZONE IN FRONT OF THE RADIATOR, IT FACES FORWARD. IT IS HIGH PRESSURE BECAUSE IT FACES THE AIR STREAM THAT
> IS COMING THROUGH THE GRILL AND LOW PRESSURE BEHIND IT BECAUSE THE RADIATOR RESTRICTS THE AMOUNT OF AIR THAT WILL FLOW THROUGH IT.
> GMC DID ADDRESS THE AIRFLOW AND ISSUED A SERVICE BULLETIN THAT INSTALLS "FLAPS" ON THE SIDES AND BOTTOM OF THE RADIATOR TO GUIDE
> AIRFLOW FROM THE GRILL INTO THE RADIATOR. I CAN'T REMEMBER IF THERE IS ONE ON THE TOP OR NOT.
>
> Third the cooling capacity is just not enough for the engine and the transmission.
>
> I BEG TO DISAGREE. IF THAT WERE THE CASE WHY ARE THERE SO MANY STOCK GMC'S OUT THERE THAT DON'T HAVE ANY COOLING PROBLEMS. ONE GMC
> NET CONTRIBUTOR NOTED THAT HE HAD OVER 300,000 MILES ON HIS BOX STOCK GMC AND HAD NEVER HAD A PROBLEM. BTW WHEN HE PUBLISHED THAT
> INFORMATION THE PERSON THAT RAISED THE SUBJECT FLAMED HIM BIG TIME.
>
> I look forward to your input.
>
> Cameron
> 1976 Palm Beach
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