1 inch min to 2 inch max, best is 1.5 inch

Stu, grab the fan that Scatpk offered. Find the stock style fan that fits the shroud the best. It'll do all you need. Chances are that flex fan is flattening out too much at idle and not pulling air.
For most cars the stock style cooling fan works great.

Forget the pusher fan. It will restrict air flow on the highway. I ran an electric 18" pusher on the hot rod. The temps went up about 10 degrees on the highway with it running. The electric motor could not spin fast enough to keep up with 60 mph air. That turned it into a wind powered generator.
With the pusher turned off the temps were still higher at speed than without the fan.

Your problem is air flow from the fan. Put the right fan on the car and it should fix it. Best of all, it'll be free (or a beer in exchange).

Some are saying the flex fan is a problem at idle. This is the only time they work well,the blades flatten out at speed not when idling.while I also recommend getting rid of it I bet It doesn't solve your problem completely.

Mopar used long fan shrouds too.
Here's a 77 New Yorker. The shroud is somewhat long. The fan blades are visible in this image too. Notice they're nowhere near the radiator.

I run the same fan in my car and zero problems, whether it's 60 or 90 my engine temp stays right at 180-185. My fan is about 2 inches from the core.

Well we sure got a lot of varing opinions on this question. I have been thinking about this all day and come to the concluesion since the engine temperture is fine even in the hottest weather when traveling at say 35 MPH+ and only goes up when there is no forced air flow at low speeds it must be lack of enough air being pulled though correct?

I think i will first try moving the existing fan back a few inches and see what does?

Also of note it takes a good fifteen minutes or at least 10 miles of travel to reach operating temps so if anything it may be running too cold at start up too.

If you're going to pull the flex fan off, go ahead and put a stock style fan back on. They work.

Stu, how "hot" is that 383 in your runner? I didn't hear it start up when I was there...I was under the impression that it was pretty stock though?

you should have no problems keeping that thing cool. look at all the high performance engines making 600 hp but driving around on the street just fine.

as others have said, your problem is definitely airflow related.

honestly, I think the key here is to move the fan further back from the radiator, so that the blades are half way in and half way out of the shroud.

And yes, flex fans are junk. they work great in theory, but not in reality. in theory, at low RPMs, they pull lots of air, but at higher RPM when you have more airflow, they flatten out from the air moving through them and thus, pull less hp away from the motor.

however, they're just junk. no matter what you do, mechanical on a clutch, electric, both...GET RID OF THE FLEXER!!!

I'm a fan (no pun intended) of electric fans, if your electrical system can handle it. when you're cruising down the highway, they are fully off, putting no load on your electrical system, or pulling hp from the engine. in town at traffic, they pull electrical load only. with a proper fan, shroud, and thermostat switch, it's as automatic as the one in your daughter's PT cruiser, you don't even have to think about it.

I'm running a 19" electric fan out of a Jeep, with a home made shroud, and my 383 stroker that's putting out 500-ish hp/tq, will sit in traffic at 170 degrees all day long...when the ambient air temps are in the 90s. and I'm using the stock radiator that came on my truck.

my fan shroud is about 20"x22" and holds the electric fan approx 2" away from the radiator--nothing fancy either, just a piece of sheet metal bent into a "box" on a sheet metal brake, and a hole cut in the middle to mount the fan.

As long as the fan is a decent fit to the shroud (diameter-wise), and most of the blade's depth is in the shroud, the space to rad core isn't critical. But 1/2" clearance is tight enough that the fan can hit the radiator on even a slight bumper impact (with stock rubber engine insulators).

No shroud, 1" fan-to-core is ideal

Rick

I had similar issues with mine - overheating at low idle speeds. For me a recore was in order and I opted to add rows /columns - increase in surface area. Basically instead of the rows being about 1/2in they are now about 3/8 inch. Once completed it solved any overheating issue -- so instead of going to the 26 inch -- recore to add more rows. It was about 350 bones but I didn't have to change any fans and it all looks stock.

Herb was nice enough to drop off a good used 7 blade stock themo clutch fan so i will try that out and take off the flex fan. Thanks Herb!

The existing thermostat is a 180 degree unit.


I always wondered if the way too radical cam has anything to do with this problem as well??

Agreed. Thermal. Ma knew. I upgraded my 26" to a 4 row afer I put the fan through it doing an burnout in reverse. $400. Nice and cool. Just say no to electric fans.

They say you want a fan 1 inch inside the schroud.

the correct position for a fan blade is half way in and out of the shroud,i thought this was common knowledge?