| [GMCnet] OT - Looking for help/advice with low and hi pressure issues [message #258767] |
Wed, 13 August 2014 20:11  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
|
Senior Member |
|
|
Hi,
Watching the good responses you have received so far reminded me of the many past posts about the effectiveness - or not - of electrically driven fans and fan clutches. The GMC requires a seriously large engine driven fan that comes on any time the incoming air temp reaches the turn on temp of the fan clutch. The fan consumes a lot more HP than one could ever get from an electric fan. Divide the watt draw of your electric fans by 760 and that will give you a rough approximation of the HP. The engine driven fan likely pulls something over 15 HP when pulling a long grade. Electric fans would have to draw something around 11,400 watts (nearly 1000 amps at 12vdc to provide the same HP). Can you imagine how big the wire would need to be to provide 1000 amps at 12vdc to an electric fan?! Not to even think about where one could generate that kind of on board power.
The other factor in your situation is how to baffle the fan to direct as much air over the radiator as you experience with the front mounted radiator at highway speeds in a GMC. I am not trying to suggest your task is hopeless, just that it is not easy. Even with great engineering not many rear engine, water cooled applications have proven to be successful as many Flexible Flyer bus owners would likely confirm. Even water cooled VW buses with far less heat and HP had a tough time once they aged over time.
My suggestion would be to do what you can to move the radiator close enough to the fan side of the engine that you can instal the same fan, fan clutch, fan surround and baffles used in the late model GMCs. Then work on means for forcing as much air as possible through the radiator at speed. Hope this helps.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed & hand crafted
in the 1907 former Masonic Temple building
in historic Kerby, OR
http://jerrywork.com
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Jerry & Sharon Work
78 Royale
Kerby, OR
|
|
|
|
| Re: [GMCnet] OT - Looking for help/advice with low and hi pressure issues [message #259091 is a reply to message #258767] |
Sun, 17 August 2014 07:41  |
 |
Bill Freeman
Messages: 122
Registered: March 2004
Location: Colerain, NC
Karma: 1
|
Senior Member |
|
|
Tony,
One more suggestion on your cooling system based on my experiences with Toronados. A Toronado has the engine mounted high so the drive axles can fit under the oil pan. The radiator is mounted low relative to the engine because of the low clearance from carburetor to hood. This results in a situation where if the radiator water level gets down any at all there will be a shortage of water in the top of the cylinder heads where it is most needed. Being a crossflow radiator in the Toronado, if the water level gets down at all it also starts uncovering the top tubes in the radiator. To avoid this problem you should make sure the top of your radiator is at least a few inches higher than the engine, or else have a remote filler tank/reservoir that is higher than the engine. On my Corvair-Olds van the radiator and the fill tank a long distance above the engine I think was a positive factor in the effectiveness of the cooling system.
Bill Freeman
78 Royale 73 Sequoia
Colerain, North Carolina
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
