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Old 04-05-2016, 03:03 PM
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mylilboo mylilboo is offline
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Default Engine is running hot.

Ok so the Malibu has been on the road for a week now and it is an outstanding machine!! Couldn't ask for a better ride! However, the engine is running really close to 210 and climbing. The bad thing is that is going 60 or so down the highway when it should be running its' coolest. OK, so here is a list of what I know about the car and what I've personally added to it:

SBC 350
Long tube headers (no name)
Mild cam of unknown specs or brands but its pretty choppy
Stock water pump
185 or 195 Thermostat (I don't remember)
TH350 stock
QP 9" with 3:70 gear
Custom aluminum cross flow radiator with 2600cfm electric 14" fan
No air dam under front bumper (important?)
No condenser
3,000 RPM @60mph 3,300 RPM @70mph
The car seems to be ok when driving around town and also at lower speeds. But as soon as I get up to highway speeds 55-65 she climbs on up.
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Old 04-05-2016, 04:59 PM
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The first thing I can think of would be make sure it is not running too lean. Can cause an engine to run hot.

Also make sure the fan is running and in the right direction.
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Old 04-05-2016, 06:52 PM
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Yeah I will check the carb again. I did in fact lean it out a little because the fumes coming out of the exhaust were insane!! Demon is a PITA to set right.

I have check the fan on several occasions and it is blowing correctly and seems to be full blast.
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Old 04-06-2016, 05:19 AM
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Anyone have any "sure fire" or "bullet proof" method to setting my 625 cfm Road Demon carb? Yes I have set the damn thing exactly how the paper shows to do it, but I think it wants the engine stock for those instructions to work. Seems like I have seen a mechanism that sits on the carb somewhere and has some sort of gauge that moves when the air fuel mix is correct. Anyone know what I'm talking about or have somethoing better?
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Old 04-06-2016, 01:19 PM
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I have a vacuum gauge but I am not sure of how accurate it is. It seems to work fine. I am checking on a 200 dollar replacement from my snapon guy tomorrow. I need my car done!!
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Old 04-06-2016, 05:46 PM
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Wish I could help. For me it was always hit or miss with carbs.
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Old 04-07-2016, 05:21 AM
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LOL yeah it seems so with me as well.
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Old 04-07-2016, 05:54 AM
LS Bonneville LS Bonneville is offline
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What temp is your fan set to come on at? Usually if you're overheating on the highway it's a coolant flow issue not an air flow issue because there should be more air flowing through the radiator naturally at higher speeds. First check to see what temp your fan kicks on at. Your car is going to run a little warm on the highway anyway because of the RPM's you're turning. The vacuum gauge will only help you set idle mixture and if it indeed choppy like you say it will always be somewhat rich at idle by design. To check your mixture at cruising speeds you will have to read your plugs or use a gas analyzer on a dyno. I'm not experienced with Demon carbs but I think they use Holley jets. Hope this helps some.
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Old 04-07-2016, 03:34 PM
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Quote:
Originally Posted by LS Bonneville View Post
What temp is your fan set to come on at? Usually if you're overheating on the highway it's a coolant flow issue not an air flow issue because there should be more air flowing through the radiator naturally at higher speeds. First check to see what temp your fan kicks on at. Your car is going to run a little warm on the highway anyway because of the RPM's you're turning. The vacuum gauge will only help you set idle mixture and if it indeed choppy like you say it will always be somewhat rich at idle by design. To check your mixture at cruising speeds you will have to read your plugs or use a gas analyzer on a dyno. I'm not experienced with Demon carbs but I think they use Holley jets. Hope this helps some.
Right on. Yeah the fan kicks on around 140. (I haven't set this yet)
I am not a noob to Chevys nor automotive general knowledge by any stretch. So that said, the only thing I am not sure of is the cross flow design of my radiator. It was built with the LS style engine swap in mind and it was built by RnD Fabrications and this thing is a massive style radiator. It compares to an old school four core in overall size. So when it started getting hot at speed, I was confused.

This said, should I start looking into high volume/high flow water pumps, or maybe even reverse flow?
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Old 04-07-2016, 03:49 PM
LS Bonneville LS Bonneville is offline
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I didn't mean to insult your automotive knowledge, if I did I apologize. The fan kicking on at 140* is way to early. It should be coming on around 200*-210*, I would recommend 200* And then shut off just below your thermostat temp. A high flow water pump can't hurt but I think it would be masking the real problem whatever that may be. You shouldn't need one. Your radiator sounds like it's more than adequate size. I would confirm the fan is working properly first before you spend any money, I'm cheap and don't like to spend my cash if it's not necessary. Personally I would add a pusher fan to the front of the radiator before I bought another water pump. Let's make sure everything you have is working like it should first. Another simple thing to check too is the area around the radiator, make sure that the air flow coming through the front of the vehicle has to flow through the radiator and can't bypass it through large gaps around the radiator. We'll figure this out, just have to put our heads together. Maybe someone else here has a different look on things.
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Old 04-07-2016, 04:25 PM
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Nah you didn't insult me. I have checked all the clearances and the flow is straight to the rad. The other thing is the shroud does not have any relief cuts or vents around the fan itself. It is also just a flat piece of aluminum and has no real curve or shape. I wonder if this could be the issue, or at least contributing to it?
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Old 04-08-2016, 08:23 AM
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Hey bro,I think you should be running a cooler thermostat. Maybe a 180.
If you're looking to get your carb tuned,inbox me.
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Old 04-08-2016, 09:24 AM
LS Bonneville LS Bonneville is offline
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Personally when I look for an electric fan I go to the junk yard and find a nice factory fan because they always move more air than the aftermarket ones and they last longer. I like the Ford Taurus ones because they fit good and pump a lot of air
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Old 04-09-2016, 06:34 AM
80driver 80driver is offline
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How about a thermostat with bypass holes. Blueprint recommended one in the install instructions. I got mine from summit.

I would also try an air dam. Cheap fix if it helps.

Fan shroud?

When I first started messing with my Bu I asked about electric fans . Most people said don't do it on a driver.

Last edited by 80driver; 04-09-2016 at 06:46 AM.
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Old 04-09-2016, 09:02 AM
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Quote:
Originally Posted by 80driver View Post
How about a thermostat with bypass holes. Blueprint recommended one in the install instructions. I got mine from summit.

I would also try an air dam. Cheap fix if it helps.

Fan shroud?

When I first started messing with my Bu I asked about electric fans . Most people said don't do it on a driver.
I have taken the March under drive system off of my car. Lets see if that was the issue. If not then I will looking to the thermostat temps.

I have just purchased a Colton racing (or something) aluminum overflow, and a new air dam. those are next regardless.

I have adjusted the temp setting on the fan controller (not happy with it) it does not show the temp ratings

and finally checked and double checked the water level and coolant mix ratios.

Yes I have a shroud, but as I said in an earlier post it is a simple flat sheet of 1/16th aluminum that my fan is mounted directly to. (I hate it, it's ugly) And the corners have no relief vents....This an issue? The Spal fans and shrouds I've been looking at, show 4-6 rubber backed vents for air flow. I wonder if this would help me?
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Last edited by mylilboo; 04-09-2016 at 09:04 AM.
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