Chevy Nova Forum banner

1 - 20 of 31 Posts

·
Registered
Joined
·
406 Posts
Discussion Starter #1
We are still stuck in a holding pattern with our fan problem. We went to install our 4 core rad using a single electic fan setup and the fan was too deep to fit between the 2-belt pulley. If we slide the fan over, the rad brace on the top will not fit also.

So.....which electric fan are you all using to fit in between this 396.

For those of you using a mechanical fan.....which are you using and which shroud since the shroud that we purchased from a member was not the one made for the big block and now we again need to consider the correct shroud and a mechanical fan.

Again, those who use a mechanical....how many are using a clutch and why?

Our car will be drawing a bunch or amps for the large stereo and a Vintage Air setup.

thanks and the faster the responses the less we will be behind after 5 years.

thanks again.
cars4kids
 

·
Registered
Joined
·
8,013 Posts
K.I.S.S.

A Flex-a-lite mechanical flex fan straight off of the water pump... No clutch that can go wrong.
 

·
Registered
Joined
·
555 Posts
A bunch of different opinions on this but I definitely like the mechanical clutch fan over my twin electric fans I had. I just put it in and dropped about 15 to 20 degrees. I did have to design and have built a custom shroud since I have an aftermarket AL radiator.
 

·
Registered
Joined
·
406 Posts
Discussion Starter #5
Okay.....I have been reading all night and other than using dual Taurus fans, many of the ppl moved back to mechanical fans.

So.....

Mechanical fan users......
1. Which fan size 16 or 17
2. Which shroud.......and is one really necessary
3. Clutch....is there really any need for one

thanks...keep the help coming.
 

·
Registered
Joined
·
471 Posts
I am having a problem. I am running 2 electric 12 inch fans each pushing 1200 cfm and a mechanical fan and it still runs 210 on a warm day in town. I haven't taken it on the highway yet.
 

·
Registered
Joined
·
2,746 Posts
hmm. Im using a set of camaro LS dual fans. Car runs cool at 170 with the stat. Only issue I do see for me in the future is they do draw some amps.
 

·
Moderator
Joined
·
6,449 Posts
I'm with Pandora's Box on this one. A mechanical fan without the clutch. It may cost a couple of horsepower but is not subject to clutch failure. My preference is GM's 7 blade flex fan. I've found them on the 70's Cadillac 500 c.i. engines but they were used on other applications. the blades are thin and do flatten out as the pump speed increases. Move a ton of air at idle where you really need it. Best to get it reasonably close to the rad(3/4") to make it draw air through the core. Too far back and the fan will pull air from the engine side not through the core. Air will move through the path of least resistance so the further away the less will come through the core. Here's one that was painted silver instead of the the factory black.

 

·
Registered
Joined
·
555 Posts
Fan - I used an 18" standard GM mechanical clutch fan

Shroud - I am a big believer in the shroud. It makes sure you are pulling air through the radiator and not just moving air around the engine compartment. If you use one make sure fan blade extend 1/2 into opening.

Clutch - I like the clutch since it does not run all the time. I used a standard GM but there are slightly different lengths that have been produced over the years. My SBC has the longer water pump so I found the shortest clutch I could find. My fan blade to radiator clearance is about 1 inch. Bottom line - use the clutch if you can make it fit!
 

·
Registered
Joined
·
8,013 Posts
Clutch - I like the clutch since it does not run all the time.
And there's the reason NOT to run a clutch mechanism. They eventually will not work properly if at all. End result - Overheating!

I'm with Pandora's Box on this one. A mechanical fan without the clutch. It may cost a couple of horsepower but is not subject to clutch failure. My preference is GM's 7 blade flex fan. I've found them on the 70's Cadillac 500 c.i. engines but they were used on other applications. the blades are thin and do flatten out as the pump speed increases. Move a ton of air at idle where you really need it. Best to get it reasonably close to the rad(3/4") to make it draw air through the core. Too far back and the fan will pull air from the engine side not through the core. Air will move through the path of least resistance so the further away the less will come through the core. Here's one that was painted silver instead of the the factory black.

Damn Shane, that's a nasty lookin' blade! :eek:

That thing looks like it'll blow like a hurricane in Florida! :D

That's gotta keep your cool for sure. :yes:
 

·
Premium Member
Joined
·
3,826 Posts
K.I.S.S.

A Flex-a-lite mechanical flex fan straight off of the water pump... No clutch that can go wrong.
I agree this is the way to go, or if room permitting, a ultra thin elect fan.

I also have a clearance problem between my inline 6 and the radiator. I went with a flex fan and no clutch, no shroud (no room!). On hot days, freeway driving, its holding around 195 with the AC on.
 

·
Moderator
Joined
·
6,449 Posts
I'm with Pandora's Box on this one. A mechanical fan without the clutch. It may cost a couple of horsepower but is not subject to clutch failure. My preference is GM's 7 blade flex fan. I've found them on the 70's Cadillac 500 c.i. engines but they were used on other applications. the blades are thin and do flatten out as the pump speed increases. Move a ton of air at idle where you really need it. Best to get it reasonably close to the rad(3/4") to make it draw air through the core. Too far back and the fan will pull air from the engine side not through the core. Air will move through the path of least resistance so the further away the less will come through the core. Here's one that was painted silver instead of the the factory black.
I indicated the need for the fan to be close to the rad but that is assuming there is no shroud. If there is room for a shroud, then definetly use one with the fan part in and part out of the shroud opening. This lets a fan pull air from the entire core instead of the diameter of the fan blade.

Here's one. $10 to fix a cooling problem.

http://www.ebay.com/itm/Flex-Fan-7-...Parts_Accessories&hash=item3a7390c6bc&vxp=mtr
 

·
Registered
Joined
·
47 Posts
I have been going through this all summer with my '68 with the 454. I've made several changes and this is what I've found.

Electric fans can't pull the cfm that a mechanical can. I only found one website that claimed they had measured mechanical OEM fan cfm, and they claim that mechanical fans pull upwards of 6,000cfm. The best electrics are pulling half that.

You need a shroud. Summit racing sells universal aluminum shrouds for $50, just need to measure what size you need then browse their selection. Just search 'universal fan shroud' on their site.

A clutch fan probably won't fit on your car unless you are running a short pump. It looks like to me that the 69-70 big block novas came with a funky 5 bladed mechanical fan with no clutch.

I am currently running a Howe aluminum radiator, 31"x20" with the summit racing aluminum shroud 28"x20"x2 9/16", with a 17" rigid mechanical fan, spaced 1/4" from the pump, with a severe duty stock replacement pump and a 196* thermostat. My car has been running about 10* over the thermostat in town, dropping a couple degrees on the freeway.

Summit also sells those rigid fans. I bought mine for $27.

An acquaintance has a '73 with a 496 and he is running a 20" fan with his engine temps slightly lower than mine.
 

·
Registered
Joined
·
670 Posts
hmm. Im using a set of camaro LS dual fans. Car runs cool at 170 with the stat. Only issue I do see for me in the future is they do draw some amps.
Im running the same fans, ive used these fans in 4 different cars. They work amazing. When first hooking them up i didnt know any better and i used a toggle and no relays. Melted the toggle and wire.

Just use good wire and relays close to the fans and battery. With 400hp and ac on in 115 temps outside it rarely goes over 180. I will never go MECH again. You can find these for 50.-150 all day.
 

·
Registered
Joined
·
682 Posts
I'm currently using a 16" electric puller fan, rated at something like 2,000cfm or so, and drawing about 10-12amps. It definitely moves less air and uses less power than the higher end fans. It works fine for my application (mild 350ci), can keep temps under 200 even on hot days, and this is all using an OE reproduction 3-row radiator and a larger water pump pulley.

Electric fans can't pull the cfm that a mechanical can. I only found one website that claimed they had measured mechanical OEM fan cfm, and they claim that mechanical fans pull upwards of 6,000cfm. The best electrics are pulling half that.
This is interesting, but at what rpm is that 6,000cfm realized? It stands to reason that a fixed mechanical fan will have variable CFM relating to engine RPM. With a single-speed electric fan, so long as the charging system is adequate, CFM should remain relatively constant. Since there is no natural airflow at idle and very little at low speeds, it seems that fan CFM is most important at these times. This being the case, I think it's important to consider the CFM capabilities of a mechanical fan at idle and low (engine) speed operation as the basis for this comparasion. So it would be very helpful to know the rpm at which that 6,000cfm figure was attained.
 

·
Registered
Joined
·
406 Posts
Discussion Starter #17
Well, we may have found an electical fan solution. Yes it may more simple to use the mechanical fan but would prefer to use electic. The problem was that we "tried" to use a single fan setup and unfortunately the motor of the fan was too deep.

So, after some research on other muscle car sites I found several big block owners using a BeCool dual fan setup with great luck. Then, after further research I discovered that ALL BeCool fans are made by SPAL...which then would lower the price.

So.....here's the fan we are looking at http://www.summitracing.com/parts/BCI-75007/

thoughts?
 

·
Premium Member
Joined
·
31,194 Posts
I use an original L78 fan and shroud, it work real well, but I swear it sounds like it can pull anyone in front of me back!:eek:

I liked using electric fans on any custom builds I've done, but I agree a straight up mechanical is fool proof.
 

·
Premium Member
Joined
·
290 Posts
Well, we may have found an electical fan solution. Yes it may more simple to use the mechanical fan but would prefer to use electic. The problem was that we "tried" to use a single fan setup and unfortunately the motor of the fan was too deep.

So, after some research on other muscle car sites I found several big block owners using a BeCool dual fan setup with great luck. Then, after further research I discovered that ALL BeCool fans are made by SPAL...which then would lower the price.

So.....here's the fan we are looking at http://www.summitracing.com/parts/BCI-75007/

thoughts?
I think that is the SPAL fan I have. It works for me on a SBC but it is a little louder than I would like. If it it the one I have it fits on a first generation V8 radiator very well. If you can get S blade fans (quieter) to fit the radiator with the same CFM rating, you may want to consider that. I think the fan you are looking at is a little cheaper on ebay.

Mike
 

·
Registered
Joined
·
47 Posts
I'm currently using a 16" electric puller fan, rated at something like 2,000cfm or so, and drawing about 10-12amps. It definitely moves less air and uses less power than the higher end fans. It works fine for my application (mild 350ci), can keep temps under 200 even on hot days, and this is all using an OE reproduction 3-row radiator and a larger water pump pulley.



This is interesting, but at what rpm is that 6,000cfm realized? It stands to reason that a fixed mechanical fan will have variable CFM relating to engine RPM. With a single-speed electric fan, so long as the charging system is adequate, CFM should remain relatively constant. Since there is no natural airflow at idle and very little at low speeds, it seems that fan CFM is most important at these times. This being the case, I think it's important to consider the CFM capabilities of a mechanical fan at idle and low (engine) speed operation as the basis for this comparasion. So it would be very helpful to know the rpm at which that 6,000cfm figure was attained.

I completely agree; and believe the variables are why we never see any stats on mechanical fans. I think this website was just making a point. They just tested some mechanical fans at their optimum pull, maybe 3,000 rpms, just to be able to get a number. Any number. Something to compare to the electrics. Everyone says the mechanical fans pull more air, but how much is more? I only added that statement because I actually read a statement that someone said they had actually tested the cfm of a mechanical fan. And what diameter fan?

I think the most beautiful thing about the mechanical, is that you can adjust the speed of it. You can raise your idle slightly to get it to spin faster, you can change your pulley ratio, and if that doesn't work, you can just accelerate a little, while you're sitting in traffic.
 
1 - 20 of 31 Posts
Top