How important is the fan shroud and the shroud extension

[Michel73]

If my 73 (350) came with a shroud extension, it is missing. Will one help with the air flow and cooling of the engine? It gets pretty warm here in Texas so I'm trying to come up with things that will help keep me running cool and clean.

Thanks for any help,

Michel

 

[Tom73]

They are a must. Without the shroud extension the fan can pull air from the side rather than through the radiator. In addition to the extension, make sure all the seals around the shroud and radiator are in place. You want all the air that the fan is moving to be coming through the radiator.

tom...

 

[Michel73]

Thanks Tom - you always have a good answer I appreciate your help. Any other good ideas to help keep the engine cooler

Thanks,
Michel

 

[78SilvAnniv]

This worked for me...

However, it has been pointed out that the GM design should not be tampered with and that it may not work for every application.

Kenny and I together have had 11 years of summer run-hot problems with the 78, replacing the clutch fan almost yearly, never solving the problem. When the warmer temps were around, we had better slow down to under 60mph or we'd run hot. AC?...try shooting up to 240 degrees!

We replaced the engine, water pump, hoses, belts, radiator, t-stat, clutch fans...everything, to no avail!
The ONLY thing that SOLVED my summer, AC and high speed (anything over 65mph) run-hot problems was a flex fan that we installed 2 years ago. I have yet to go over 195 degrees at any speed, any time of year, with or without the AC running at hwy speeds or at slow speeds in town.

Regardless, the fan shroud and all it's parts must be present and working properly for any fan to do its' job.
Heidi

 

[Michel73]

Thanks for the info Heidi. Where did you find your "flex fan" ? I looked in Corvette America and did not see one. I'll check in Eckler's tonight.

Michel

 

[78SilvAnniv]

Flex Fan

I purchased mine at a local speed shop but I think they are also available through Summit.

I believe mine is a Flex-a-lite. It is metal, blue spokes with aluminum blades. The spacer for a Corvette is particular and comes in TWO pieces. BE SURE to specify it is for a Corvette.
I think it needs two spacers to get the fan blades in the proper position within the shroud.
Heidi

ps I have pics of my application if you would like to send me an email through CAC I can send you a return email with the pics. Click on my profile (blue highlighted name) and scroll down, left side, option to send email.

 

[JVSBob]

Michel73,

I've been a chevy performance freak in Phoenix for going on 20 years. I've had a lot of experience with trying to keep the engine cool in summer. 78SilvAnniv's advice to go with a flex fan is a good idea. in some cases the flex fan will increase horsepower over stock, but you must use a fan equal in diameter to the stock clutch fan. Also, the stock shroud and the stock shroud sealing kit need to be in place. My 68 roadster used to run at 230 in the summer. When I installed new rubber seals on the shroud, it dropped to 210 and never ran hot again. Another idea to try is running a mechanical fan (flex or clutch style) along with an electrical fan attached directly to the back of the radiator in a pull type configuration. The only trick here is to make certain that the electrical fan runs in the direction OPPOSITE the mechanical fan. I did this trick on a 400 horsepower small block Camaro, and the car never overheated in city traffic with the AC on. Hope this helps. Good luck with your 73.

 

[78SilvAnniv]

Another idea to try is running a mechanical fan (flex or clutch style) along with an electrical fan attached directly to the back of the radiator in a pull type configuration. The only trick here is to make certain that the electrical fan runs in the direction OPPOSITE the mechanical fan.

I need a little clarification, please...
Do you mean opposite as in one blows air from the radiator toward the headlights and nose and the other blows air from the radiator towards the engine?
Seems to defeat the purpose, that is why I am :confused
OR...
Do you mean the fans both pull air in the same direction (from the radiator towards the engine) but the blades rotate in opposite directions?
This sounds like a good idea, but why do they need to spin opposite to each other?
Heidi

 

[crebo]

I'm with Hiedi and the flex fan. I just put my flex fan on and it makes a huge difference. Hadn't went over 200 with my big block.

Crebo

 

[drduckster]

fan shroud

don't forget the front spoiler, the beginning of the cooling process, my .02. :cool

 

[Michel73]

drduckster,

Yes - you are right. You know the crazy thing is that I have no front spoiler and no fan shroud extension, only a regular seven blade fan and the thing still runs OK. But I'm trying to be proactive and get ready for this Summer and the National Corvette Caravan

Thanks for the help,

Michel

 

[drduckster]

fan shroud

It may not fix all over-heating....... it dropped my highway temps about 15 degrees. weather here in summer high heat.... high humidity. I run at 195 now.

 

[JVSBob]

Heidi,

Sorry for the confusion. I mean that if your flex fan runs counter clockwise, then your elec. fan should pull air through the radiator while turning in a clockwise direction. The physics behind this is that the elec. fan is creating a high pressure air pocket inside the shroud. This high pressure air is also turning clockwise due to the inertia of the electrical fan. The clockwise movement of the air, when contacted by the high velocity counter clockwise movement of the mechanical fan blades, allows the blades to displace more of the air from within the shroud. Visualize a cheese grater. The more pressure you put on the cheese, the thicker the slices. The net effect is that the total CFM of air moved through the radiator will be the sum of both fans individual values (eg 1000CFM electrical + 800CFM mechanical = 1800CFM total). If both fans turned the same direction, then the total CFM of air through the radiator would only be equal to the greater of the two fan's values plus the difference between the two fans (eg. 1000CFM electrical + (1000CFM electrical - 800CFM mechanical) = 1200CFM total).

Sorry if all this Engineering talk bores everybody.

Another way to REALLY cool down your vette (especially big blocks) is to replace the brass radiator with an unpainted aluminum radiator. Aluminum disipates heat nearly twice as effectively as brass. I built a 500+ HP big block with AC for a customer here in Phx. I used an aluminum radiator with the dual fan concept we have been discussing and his car ran at the 195 degree thermostat temp, even when it was 115 outside.

 

[Bob Chadwick]

Sorry if all this Engineering talk bores everybody.

Doesn't bore us but confusion is a whole other issue.

 

[78SilvAnniv]

I got it now!

...the fans both pull air in the same direction (from the radiator towards the engine) but the blades rotate in opposite directions...

I understand the concept and I really like the idea that the overall air moved can be so great with the addition of both fan cfm's. Great idea!
Heidi

*married to a power plant operator...I have learned to understand "engineering-ese"...