Seven blade flex fan
Thread Starter
ZR1TG
Joined: May 2005
Posts: 875
Likes: 235
From: South florida
Seven blade flex fan
Installed seven blade flex fan on 1969 300hp 𝐀𝐮𝐭𝐨 with factory ac. Rear was running real hot at idle with ac on only 230 degrees. Seven blade made no difference . In fact a little warmer at highway speeds but highway speeds have always been fine . The radiator has been
gone through the shroud is sealed . Beginning to think just not gonna ever idle here in south floirda in summer with original ac compressor ?
gone through the shroud is sealed . Beginning to think just not gonna ever idle here in south floirda in summer with original ac compressor ?
Race Director
Joined: May 2006
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Likes: 2,583
what temperature thermostat are you running?
is the thermostat a large mouth thermostat such as the one in this link? https://www.summitracing.com/parts/b...iABEgIXvfD_BwE
have you considered an aftermarket water pump such as a FlowKooler which uses a modified impeller?
are you running your distributor vacuum advance to a manifold source so that it advances at idle?
what is your initial timing set for?
is the thermostat a large mouth thermostat such as the one in this link? https://www.summitracing.com/parts/b...iABEgIXvfD_BwE
have you considered an aftermarket water pump such as a FlowKooler which uses a modified impeller?
are you running your distributor vacuum advance to a manifold source so that it advances at idle?
what is your initial timing set for?
Drifting
Joined: Aug 2009
Posts: 1,346
Likes: 160
From: new iberia la
We have the same climate here on coast of Louisiana as you have in Florida .. its 111* heat index today.. and my car does not run hot, with A/C on ,ever..... you have another issue .. maybe a leaking head gasket putting air bubbles into coolant.. or late ignition timing producing heat..bad or incorrect waterpump , loose worn slipping fan belt.. blockage in radiator.. fan not inside edge of shroud.. closed heat riser valve .......something is not right..
Le Mans Master
Joined: Mar 2004
Posts: 7,499
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From: Little Rock AR
Do not use an aftermarket fan. The factory setup will work.
Thermostat can be checked. IR heat gun would be a nice tool to have here.
Full ignition recurve would help if you have not already completed it.
Thermostat can be checked. IR heat gun would be a nice tool to have here.
Full ignition recurve would help if you have not already completed it.
Is my vette stock?? HAHA
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
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You could go to electric fans. I run 160* thermostat to get the coolant flowing at a lower temp, I put in a good size electric fan and a lower "on" sender. It comes on at 185*, off at 175*. and for cooler highway speeds I put in a larger air dam. Its running very cool on the highway now and the newer lower electric fan T stat kept me below 150* yesterday and last night. THe ambient was only around 85* though. Increasing the airflow for anything above 30 mph will help with the cruise temp and a strong electric fan will help with idle. If you want to keep the "original" fan look get a good clutch fan, youre not going to beat its performance with a flex fan.
The timing is always a good thing to check but with todays crap fuel you may have detonation before the timing overheats your car. And everyone seems to overlook the lower radiator hose needing an anti collapse spring inside it The hose companies are producing the hoses but not installing the anti collapse spring. You definitely need it
The timing is always a good thing to check but with todays crap fuel you may have detonation before the timing overheats your car. And everyone seems to overlook the lower radiator hose needing an anti collapse spring inside it The hose companies are producing the hoses but not installing the anti collapse spring. You definitely need it
Thread Starter
ZR1TG
Joined: May 2005
Posts: 875
Likes: 235
From: South florida
We have the same climate here on coast of Louisiana as you have in Florida .. its 111* heat index today.. and my car does not run hot, with A/C on ,ever..... you have another issue .. maybe a leaking head gasket putting air bubbles into coolant.. or late ignition timing producing heat..bad or incorrect waterpump , loose worn slipping fan belt.. blockage in radiator.. fan not inside edge of shroud.. closed heat riser valve .......something is not right..
compressor or late mode replacement ?
Thread Starter
ZR1TG
Joined: May 2005
Posts: 875
Likes: 235
From: South florida
do have and ir heat gun and the temperature the cars gauge is reporting is accurate.
Timing set up following Lars advice. 36 degrees in before 3k works out to about 12 degrees initial in this car. Detonation is a problem though once it gets hot but not when cold
Thread Starter
ZR1TG
Joined: May 2005
Posts: 875
Likes: 235
From: South florida
You could go to electric fans. I run 160* thermostat to get the coolant flowing at a lower temp, I put in a good size electric fan and a lower "on" sender. It comes on at 185*, off at 175*. and for cooler highway speeds I put in a larger air dam. Its running very cool on the highway now and the newer lower electric fan T stat kept me below 150* yesterday and last night. THe ambient was only around 85* though. Increasing the airflow for anything above 30 mph will help with the cruise temp and a strong electric fan will help with idle. If you want to keep the "original" fan look get a good clutch fan, youre not going to beat its performance with a flex fan.
The timing is always a good thing to check but with todays crap fuel you may have detonation before the timing overheats your car. And everyone seems to overlook the lower radiator hose needing an anti collapse spring inside it The hose companies are producing the hoses but not installing the anti collapse spring. You definitely need it
The timing is always a good thing to check but with todays crap fuel you may have detonation before the timing overheats your car. And everyone seems to overlook the lower radiator hose needing an anti collapse spring inside it The hose companies are producing the hoses but not installing the anti collapse spring. You definitely need it
This is a very original car nut and bolt restoration trying to keep it all oem didn’t want to put flex fan but do want to drive it in summer . The very reason I bought a factory ac car. Will check lower hose.
Again it only runs hot when idling with ac on otherwise it’s fine.
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Thread Starter
ZR1TG
Joined: May 2005
Posts: 875
Likes: 235
From: South florida
what temperature thermostat are you running?
is the thermostat a large mouth thermostat such as the one in this link? https://www.summitracing.com/parts/b...iABEgIXvfD_BwE
have you considered an aftermarket water pump such as a FlowKooler which uses a modified impeller?
are you running your distributor vacuum advance to a manifold source so that it advances at idle?
what is your initial timing set for?
is the thermostat a large mouth thermostat such as the one in this link? https://www.summitracing.com/parts/b...iABEgIXvfD_BwE
have you considered an aftermarket water pump such as a FlowKooler which uses a modified impeller?
are you running your distributor vacuum advance to a manifold source so that it advances at idle?
what is your initial timing set for?
Drifting
Joined: Aug 2009
Posts: 1,346
Likes: 160
From: new iberia la
Thread Starter
ZR1TG
Joined: May 2005
Posts: 875
Likes: 235
From: South florida
advance source from carb to manifold and rpm increased 200 rpm and temp dropped a little to 220 and holding first time its held . Not sure if that’s from the advance or the xtra 200 rpm and flex fan . Nice to see it not climbing anymore though
Drifting
Joined: Aug 2009
Posts: 1,346
Likes: 160
From: new iberia la
Thanks for that info fishslayer. So I am clear , your car can sit at idle as long as you like 15 minutes say with ac on and what temp do you run at that point ? I just pulled thermostat completely for a test and made no difference just took longer to get to 230 and slowly climbing. I then switched vac
advance source from carb to manifold and rpm increased 200 rpm and temp dropped a little to 220 and holding first time its held . Not sure if that’s from the advance or the xtra 200 rpm and flex fan . Nice to see it not climbing anymore though
advance source from carb to manifold and rpm increased 200 rpm and temp dropped a little to 220 and holding first time its held . Not sure if that’s from the advance or the xtra 200 rpm and flex fan . Nice to see it not climbing anymore though
Last edited by fishslayer143; Aug 12, 2019 at 12:43 PM. Reason: spilled my beer
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,216
Likes: 9,354
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Have you ever pulled the radiator out and had it back flushed to get all the crap out of it?
Drifting
Joined: Aug 2009
Posts: 1,346
Likes: 160
From: new iberia la
I have a C5 as well. C5s have a very different cooling set-up.. known overheating issues.. But C5s run hotter anyway, High fans does not even engage til 238* ...and they are bottom feeders, .I ll bet that if you remove the top mounting panel on your C5 radiator and look between the Radiator and A/C condenser, you will see 1/4 to 1/3 of your radiator covered up in leaves, plastic bags, bird winds and other debris.. Its not enough to clean the front of Condenser , you must clean out BETWEEN the two.. and turning A/C on high engages fans at a stop..
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Here are a couple of pictures of what other members have found when clearing the debris from that area at the front of the car.
It shouldn't be necessary to remove them from the car to clear them out unless they are packed with debris and have never been cleared before. Be careful about applying too high a pressure of air or water to the radiator/condenser as it can result in damage to the fins of an older unit.
Good luck... GUSTO
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Hardhat, you've mentioned a couple of times that you installed a 'seven blade flex fan'. When you removed the original unit, is it correct to assume that you removed the original rigid fan and clutch as a unit? That you then installed the flex fan directly to the mounting flange on the water pump? Not questioning your knowledge or skill, just trying to clarify. 
Can you post a picture of what you have installed now that shows how it was mounted in relation to the fan shroud in particular? The fans relationship with the shroud can have a significant effect on how efficiently it functions. Also how much of a gap remains between the tips of the fan and the shroud as well.
Chevrolet did offer a 7-bladed fan with clutch on some cars with A/C in place of the normal 5 blade fan. If the clutch unit is functioning properly they generally do a good job of cooling these cars, even those with the big block engine.
Good luck... GUSTO
Can you post a picture of what you have installed now that shows how it was mounted in relation to the fan shroud in particular? The fans relationship with the shroud can have a significant effect on how efficiently it functions. Also how much of a gap remains between the tips of the fan and the shroud as well.
Chevrolet did offer a 7-bladed fan with clutch on some cars with A/C in place of the normal 5 blade fan. If the clutch unit is functioning properly they generally do a good job of cooling these cars, even those with the big block engine.
Good luck... GUSTO
Le Mans Master
Joined: May 2007
Posts: 5,028
Likes: 1,120
From: North tonawanda NY
Ive always read that a properly setup factory fan and shroud with a good clutch would work better than a flex fan which actually does very little cooling at higher rpms because the blades flex flat and stop pulling air...
When I replaced my engine and rad I had purchased a heavy duty fan clutch which is supposed to spin with better lockup .. it works well for me with a 180 stat my temp gauge stops just below 200 and never goes over that. my car does have ac but it no longer works so not really the same situation as you but just sharing what I experienced...
My uncle has a 76, he bought the car with a flex fan installed and no shroud.. it ran hot and overheated constantly we put the factory shroud on and replaced the flex with a clutch and factory fan and it no longer overheats but im sure the shroud had a lot to do with it.
When I replaced my engine and rad I had purchased a heavy duty fan clutch which is supposed to spin with better lockup .. it works well for me with a 180 stat my temp gauge stops just below 200 and never goes over that. my car does have ac but it no longer works so not really the same situation as you but just sharing what I experienced...
My uncle has a 76, he bought the car with a flex fan installed and no shroud.. it ran hot and overheated constantly we put the factory shroud on and replaced the flex with a clutch and factory fan and it no longer overheats but im sure the shroud had a lot to do with it.
Race Director
Joined: Apr 2003
Posts: 19,352
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From: Tampa, Florida
I have a C5 as well. C5s have a very different cooling set-up.. known overheating issues.. But C5s run hotter anyway, High fans does not even engage til 238* ...and they are bottom feeders, .I ll bet that if you remove the top mounting panel on your C5 radiator and look between the Radiator and A/C condenser, you will see 1/4 to 1/3 of your radiator covered up in leaves, plastic bags, bird winds and other debris.. Its not enough to clean the front of Condenser , you must clean out BETWEEN the two.. and turning A/C on high engages fans at a stop..
Yes, did all that. C5's are hot running cars.
Drifting
Joined: Aug 2009
Posts: 1,346
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From: new iberia la