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Old 09-28-2013, 01:13 PM
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Fan shroude and fan spacing for best cooling SBC

Hello guys me again I hope to get some advice here. I just got done installing a proper shroud for my 96 s10 with a SBC and it does excellent going down highway or moving but the problem I have had since day one is it not staying cool at idle. I am using a 29 x16 two row one inch each all aluminum radiator and you can put your hand on the radiator in the front and you can feel it pulling a good bit of air and you can feel no air escaping the shroud we just installed on it last week. I am running a 17 inch flex fan ( standard 160 t stat) and tried to run a clutch fan but with the clutch it hits the radiator and it has no more room to go forward as its already in the forward position. Looking at the pictures does everything look like its setup good? I drove it yesterday and I did not let it sit too long but in traffic it is 180 coming off the interstate and in stop and go traffic it starts to climb pretty easy and does not take long to do so. The most so far it got was about 200 but I almost bet it might get hotter but how hot I don't know yet as I have not really let it sit for a long time to really see if its working good enough yet but I feel like what I currently have still might not be enough but I need to test that another day later on in the week. From what I read fan placement is also very critical and I currently have a two inch spacer on the fan and the fan depth is 2 1/4 inch. I did buy a seven blade 2 1/2 flex fan to try and put on my truck. Do I need maybe to go back a 1/2 inch on my spacer to set the fan closer to engine and not as close to the radiator or does it look good where it is? I can not use a high flow thermostat as it makes it run to cold on highway and at idle. So what do you guys think. I value your opinions. Electric fan setup is out of budget for this year as I got other things to catch up on but I have read other s10 v8 swaps out there are running similar setup as mine with no at idle heat issues and are using a plain old flex fan and even a smaller radiator with only a single 1 5/16 inch row of colling.
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Old 09-28-2013, 01:21 PM
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Fan looks like it's sitting maybe slightly too far into the shroud, (but close!) but what is more questionable is the fan to shroud clearance. Looks like too much clearance between the fan and shroud, so it allows the fan to pull air from around the engine compartment, instead of through the radiator.
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Old 09-28-2013, 02:09 PM
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If I put my hands at the side of the shroud you can not feel any air around it or below it just from where it pulls from inside the shroud itself. I know the picture makes it kind of like there is a lot of clearance around the radius ( if that's what your talking about) but there is actually not very much at all as we had to clearance it a little at the bottom in order to clear the fan correctly and allow it to not be touching anything as it spun around
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Old 09-28-2013, 02:20 PM
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Running about 205-210 is a good max temp, but anything up to about 225 is not any problem. You really want to run hot enough to get good engine efficiency. I would use a 195 degree high flow thermostat to get good flow and reasonable temps. This may actually improve cooling at idle and still keep good highway temps.

It does sound like you need a little more air flow since it hit 200 at idle with a 160 thermostat. You could try using a big box fan in front of the radiator while idling to see if more air helps.

Bruce
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Old 09-28-2013, 02:57 PM
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Quote:
Originally Posted by eric32 View Post
I am running a 17 inch flex fan
Never did like a flex fan. Don't like the concept and don't like the results. The whole idea of a flex fan was to supposedly free up some hp from not having to turn a high-pitch fan. DONKEY DOOKEY. It still takes power to lay down the blades, so where's the benefit? I'll tell you where it is, in the manufacturer's bank account. Replace that fosdick unit with an OEM 7-blade, 18" diameter steel fan blade that has at least a 2 1/4" pitch. Lay the fan down flat on the work bench and measure from the work bench surface to the edge of one of the blades to find the pitch. The most agressive fan I have ever seen was from a '78 to '85 Oldsmobile diesel. I can't remember the pitch exactly, but I remember it being around 3" and moving an incredible amount of air.

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standard 160 t stat
No, No, No, No, No. When you're trying to figure out how to do things that will work, you normally don't have to look any further than the way the OEM's do it. Have you ever seen a 160 degree thermostat in an OEM application? No, they're upwards of 190. There's a reason for that. First, the motor will use fuel much more efficiently at higher temps. Secondly, the higher temps will help to burn off acids and other by-products of combustion that will adulterate the oil. Chuck that fosdick 160 over the fence and install a real thermostat. Any of your neighborhood suppliers (Autozone, Checker, O'Reilleys) will have 190/195/200 thermostats that will fail in the open position and cost under 10 bucks.

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Originally Posted by eric32 View Post
tried to run a clutch fan but with the clutch it hits the radiator and it has no more room to go forward as its already in the forward position.
BZZZTTT. Wrong answer. You're either a hot rodder or you're not. If you are, then it should be no real feat to move the radiator forward and fabricate mounts off the core support. If you're not, then have someone do it for you. I did a 302 Ford swap into an '83 Mitsubishi pickup and moved the radiator forward 2 3/4" so that I could use all the Ford factory fan, fan clutch and radiator.

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Originally Posted by eric32 View Post
it is 180 coming off the interstate and in stop and go traffic it starts to climb pretty easy and does not take long to do so.
If it cools to 180 on the freeway, (fan is not needed above 35 mph) then you have enough radiator surface area and enough area in the engine bay for the hot air to escape. The problem at idle then, is that the fan is not moving enough air through the radiator. Chuck the flexy-flier over the fence and install a real fan blade with enough pitch to move some air.

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Originally Posted by eric32 View Post
From what I read fan placement is also very critical and I currently have a two inch spacer on the fan and the fan depth is 2 1/4 inch. I did buy a seven blade 2 1/2 flex fan to try and put on my truck. Do I need maybe to go back a 1/2 inch on my spacer to set the fan closer to engine and not as close to the radiator or does it look good where it is?
The fan blade should be as close as possible to the radiator core without touching it at max engine revs. Three-quarters of an inch to one inch from the face of the radiator core to the front edge of the fan blade has worked well for me in the past.

Quote:
Originally Posted by eric32 View Post
I can not use a high flow thermostat as it makes it run to cold on highway and at idle.
This makes no sense at all. The purpose of a thermostat is to regulate the cooling water temperature in the water jackets of the motor. If you install a 190 thermostat, then the motor will not run UNDER 190 once it has warmed up from cold.

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Originally Posted by eric32 View Post
Electric fan setup is out of budget for this year as I got other things to catch up on but I have read other s10 v8 swaps out there are running similar setup as mine with no at idle heat issues and are using a plain old flex fan and even a smaller radiator with only a single 1 5/16 inch row of colling.
I'm glad an electric setup is out of budget for you. I hate the damned things. No electric setup ever conceived and designed by man will move as much air as a properly designed engine-driven steel fan with a properly-engineered thermostatically-controlled fan clutch.

Last edited by techinspector1; 09-28-2013 at 03:03 PM.
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Old 09-28-2013, 03:13 PM
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I don't have any room for a pusher fan as the radiator core support was cut in order top put the radiator forward in order to run a mechanical fan and make some space. This thing really does pull a lot of air through the radiator as it will hold and pull a piece of paper clear out of your hand and you can fell it coming straight through the shroud and not anywhere around it.

I have only a 1.5 spacer not a 2 inch so sorry for the misinformation on that. I measured and my fan only sticks out about a half of an inch from inside of the shroud but I do have about one inch clearance inside the shroud around the radius according to the instructions that came with my fan that is good on that part. I also have about 1 and a quarter inch clearance of the fan from the radiator so good on that part.

According to my math current fan needs to be 1 and an 1/8 inch from the outside of the shroud. If I were to use a 1.250 spacer I would then go from a half inch out to 3/4 or if a 1 inch spacer I would be exactly one inch out which is about as close as I can get.

Now if I put my new fan on according to the math it needs 1.25 for best placement and with current spacer it would be about 3/4 which is not enough and with a 1.25 spacer it then would be one inch and 1.25 with a one inch spacer so that sounds like that is what I need to do but I don't know if I will have enough clearance towards the engine to take the fan that far back. Does it really make that much of a difference in fan depth for just a quarter of an inch?

I know I would have enough room to use a 1.25 spacer but the one inch would be cutting it really to close.

My wifes 2000 envoy has the half in and half out placement of the clutch fan but on my brothers full size chevy truck his fan is pretty much all inside the shroud. Thanks for you tips.

I used a 180 high flow thermostat before and it makes it run too cold down highway at around only 160 degrees and even colder in winter time and putting cardboard across the radiator still does not help on that part which is why I run a normal t stat instead of a high flow.

I have used a normal 180 t stat and it does the same as it does not with the standard 160 and makes no difference and if I were to use a 195 high flow I wonder if it would do no different then the 180 high flow did. It kind of bites that one way is too much cooling and the other is just fine highway but just not enough at idle but is very close. Wow tech I did not get your response till after I typed this so I understand about the factory style clutch fan setup I had my Dad do the custom work of moving the radiator forward and it was moved over two plus inches forward from the factory spot and if I was running a smaller thickness radiator such as bigger size single core like the s10 swap books call for ( late 80's corvette radiator) then I would have enough room for a clutch setup but I have had similar size radiators like that before and they was not enough to keep it cool in either way.

I can't do all of what you said but I am willing to chuck the 160 t stat over the fence and try a high flow 195 and see how it goes. I will even try a 195 standard and see how it does too heck I have nothing to loose here. Thanks for the info.

Last edited by eric32; 09-28-2013 at 03:27 PM.
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Old 09-28-2013, 05:18 PM
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Clearance may well have been too close on the bottom, but I can clearly see it's not close on the top half. A fan should be close enough to not pull air in from the engine side as it's pulling through the radiator. Since you're cooling well at freeway speeds, then it tells me that there's not enough air flow at idle. A smoke test will show if it's pulling air from the engine side also, and just recirculating it. At freeway speeds you could get by with no shroud and work fine.
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Old 09-28-2013, 05:24 PM
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Ok I just found a video comparing a normal oem stant thermostat and a stant superstat and both were 180 and at the 200 degree mark the oem stat was all the way open and the superstat was only somewhat open and I guess from reading the superstat allows the vehicle to run hotter with less opening and closing of the thermostat compared to an oem style that opens and closes more often in order to regulate engine temp and the superstat has a 50 percent stronger load on the spring compared to a oem. That is what they are saying about there thermostats so I do have one of those in my truck right now and is a 160 and that could be my problem is it allowing engine to get warm but yet is allowing it to keep to warm and not opening up enough at idle to allow proper flow and that is what my engine needs is more flow. So I went ahead and got a 180 and 195 just plain oem style thermostat to try and hopefully that is the last piece of my puzzle as I do know proper thermostat goes hand and hand with everything else. Thanks tech for the heads up.
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