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Old 09-17-2011, 05:16 PM
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Best Place for Temp Sensor for Electric Fan?

My streetrod only has one opening on the intake manifold for a temp sending unit. If I use that one for the temp gauge, I don't have another for the electric fan. What can I do? I have a 350 chevy. Any ideas would be appreciated.

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Old 09-17-2011, 05:25 PM
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They make waternecks (where the radiator hose connects) with temp gauge holes in them. Im not sure if they make pretty ones but Ive used cast ones in the past
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Old 09-17-2011, 05:56 PM
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tRY A THERMOSTAT housing for a 78 chevy pick up
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Old 09-17-2011, 07:03 PM
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No holes in the heads that can be used?
I know my temp sender is there.
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Old 09-17-2011, 08:32 PM
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I assumed you did not want to use the plugged holes in the head one by cylinder 6 & 8 and a bit hotter on the other side by cylinder 1 & 3.
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Old 09-18-2011, 06:42 AM
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depending on your sender you can tap into it and control the gauge and the fan controller. Dakota digital does this type setup.
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Old 09-18-2011, 06:57 AM
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Another option would be to
use a sender that will fit in the radiator petcock hole.

You would have to use a sender that comes on real low tho.

on @ 180
off @ 160

Could also remove the intake (not absolutely necessary) and drill and tap for another sender.

I'm sure there is a boss somewhere on the intake for an additional hole.

I just too a brand new manifold in to get drilled for a fan switch on my 66 Elky
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Old 09-18-2011, 10:25 AM
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A temp sensor in the head will indicate hotter than one in the T-stat housing by as much as 15 degrees.

Vince
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Old 09-18-2011, 11:39 AM
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you wouldn't want a radiator fan sensor in your engine, it would always run when the motor got up to temp.

i used a short piece of exhaust pipe in my lower radiator hose. i welded half of a 3/8 pipe coupling in it for the fan sensor. also weld on a ground stud to ground the tubing and sensor.

my thoughts for using the lower hose? i figured to let the radiator do it's job cooling coolant, if it comes out too hot; then turn the fan on.

if you put in the thermostat housing or the upper hose, your fan will run as soon as the thermostat opens. even if there is ice in your radiator.
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Old 09-18-2011, 09:09 PM
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Thanks, guys for all the great advice. If I use a sensor on one of the cylinder heads, what temp sensor should I get? If this setup will indicate hotter, should I go with a 190 degree? With the sensor on the lower hose, like Ogre suggested, would the temp sensor be of a lower rate, say 180 degrees?
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Old 09-18-2011, 10:43 PM
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I use a 195* switch in the passenger head and a180* Robert Shaw high flow thermostat in the manifold. The thermo. keeps the water at 185* until it needs some cooling and then it cycles off, only on when needed.
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Old 09-19-2011, 05:09 AM
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On the last system I designed (small block Ford) I put it in the water passage on the intake. It's been a while but I think I used a fan-stat from a chrysler application. It came on much cooler than the Ford and Chevy ones.
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Old 09-19-2011, 05:30 AM
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Your engine temp at the manifold will run at the thermostat temp (e.g., 195) or about 5 degrees higher (195-200) if everything is working right. You want the fan to kick in if it gets to about 5-10 degrees higher than the thermostat temp, and to kick off when it gets about 5-10 degrees lower than the thermostat. With a 195 thermostat I think I would have the fan kick in at 200 and turn off again at about 185.

I've run my temp sensor mounted on the passenger side head fitting and on the intake manifold, and did not find a lot of difference in measured temp. I think the measured was always within about 5 degrees.

Bruce
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