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Old 05-27-2012, 05:43 PM
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engine overheats at hiway speeds

car runs 170 ish with electric fan running on city and rural streets.
at hiway speeds the car climbs up to 200 and rising, even with the electric fan running.
Ive installed a lower closeout panel
http://undercoverinnovations.com/ind...b0ec9f819e7c5c
its supposed to help cooling but does the opposite on the hiway???
guess ill try with it removed.
car never overheated with the mechanical fan.
since installed a high output electric with 2800 cfm and full shroud
pic here.

185 degree temp switch.
radiator is a 2 core sized for BB chevy.
I did notice the inlet of the rad was squished a bit to allow welding to the side tank.
(might be a restriction)
upper hose is hard when at proper temp.
the shroud and fan covers the whole core area
pic:

I ran a direct mechanical 6 blade fan with factory shroud (always spinning) temps stayed 165 to 175 with the radiator im using now and upper closeout panel.
All i added was the above electric fan/ shroud with 185 degree temp switch and lower closeout panel.
I even uncorked the usually blocked rear water passages and ran hoses bypassing the thermostat to aid in cooling.

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Last edited by dawg; 05-27-2012 at 05:48 PM.
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Old 05-27-2012, 06:20 PM
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I had the exact same problem with same setup on my '32. Took the shroud off, solved problem. Shroud won't let enough air pass thru at speed.
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Old 05-27-2012, 07:28 PM
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Go here and read about cooling: http://www.crankshaftcoalition.com/w...cooling_system

Two core rad....Big block......no!
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Old 05-27-2012, 07:39 PM
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2 core aluminum rad made for big block but I have a smallblock lol.
I read somewhere to install rubber flaps that open at highway speeds!
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Old 05-27-2012, 07:45 PM
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Also make sure that lower hose is not callapsing at speed. That needs to have a coil spring in it to keep it open.
Usually overheating on highway is not enough cooling system, overheating in driveway, not enough air flow. Might need 3 row radiator
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Old 05-27-2012, 08:06 PM
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I cut 4 holes in my rad shroud & installed rubber flaps, no help. But, what works 4 1 person won't work for anutter. Is that a 16in puller fan?
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Old 05-28-2012, 06:25 AM
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yes spal HP puller 2025 CFM.
the cooling sytem is good rad is more than big enough.
Keep in mind the system wasnt an issue with factory shroud and mechanical fan!
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Old 05-28-2012, 07:30 AM
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If the timing is a little slow it will make an engine run hotter on the highway. Won't cost anything to double check it.

John L
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Old 05-28-2012, 07:47 AM
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chatted with the local radiator shop owner while the wife and i had breakfast in a local diner.
He stated that my problem is common with the custom shrouds.
they cool good under 30 mph or so but fail to cool at anything higher.
he said additional holes need to be made in the shroud and thin rubber flaps will need to be placed over holes.
by thin he ment .010 to no more than 1/32"thick rubber so incoming air will open them causing flow through the radiator and suck closed at lower speed.
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Old 05-28-2012, 07:50 AM
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Quote:
Originally Posted by John long
If the timing is a little slow it will make an engine run hotter on the highway. Won't cost anything to double check it.

John L
Timing was checked and rechecked .
I even had the car on the sun diagnostic machine (remember those?)
all plugs firing good and timing is perfect.
I even had the distributor (new unilite) put on a distributor machine to check it.
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Old 05-28-2012, 08:36 AM
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since it only overheats at highway speeds, it could be that more air is flowing around/under/over the radiator than thru it.
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Old 05-28-2012, 09:34 AM
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H Dawg, thank you for your service haven't seen you around much or for a while. You probably know what i am going to say but here it is anyway, loose the electric fan go back to a good stock style mechanical or a real good aftermarket fan With a shroud. JMO and if you want to continue to use the pulley set-up you have on it now which i really like. just machine the water-pump pulley so the mechanical fan is recessed in the pulley and then all should be good. I have been there done that Dawg either way good to see you again. If you need pics of exactly what i done on my pulleys let me know .


Cole
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Old 05-28-2012, 11:13 AM
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That fan / shroud setup is not allowing ample air flow at speed. Looking at it it is probably covering about 30% of the radiator. this will cause air to go around instead of through. Sealing the top of the radiator to the support may help a little. On the highway that shroud is doing more harm than good. On the highway you don't need a fan as natural airflow should be more than enough.
You said it worked fine with the stock fan and shroud, this tells the whole story.
If you have a manual switch on the fan try turning it off on the highway and see if it helps, the fan can also impede air flow.
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Old 05-29-2012, 04:29 PM
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the mfg suggest I kick out the bottom for a 1/2 to 1.0" gap to allow air to flow.
if it works I should place a few 2" holes with 1/32 rubber flaps to correct issue.
if angling doesnt work they offered to refund my money for the shroud/fan assy.
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Old 05-29-2012, 05:36 PM
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That lower close out WILL NOT WORK.
It traps air under the hood.
I have never seen that on any origional GM car

That is where the hot air gets out.

You need 4000cfm of fan flow.
Get the origional GM 7 blade clutch fan and a fan shroud.
Install a chin spoiler directly under the rad support
just like on the OEM cars.
This chin spoiler creates a negative pressure under the car and under hood so air can flow thru the rad and out of the engine bay under the car.
Air always flows from high pressure to low presssure.
Take that stupid thing off and ditch the restrictive too small electric fan.
The electric fan is blocking air flow thru the rad at hiway speed too.

No amount of cutting little flaps in that thing is going to fix it.
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