I'm running an AutoRad radiator in front of my SBC and continue to have mild cooling issues. I've got the fuel/air mixture as well as the timing dialed in but still experiencing overheating after idling awhile. I currently have a 15" fan on the pulley, and wondering how much a 17" fan might improve things? I can't find anything that correlates mechanical fan diameter to CFM, so hoping one of you guys might know. FYI, I'm running a pusher fan on the front, as well. It only overheats after idling for 20-30 minutes, and it's a slow creep. Seems to me its an airflow issue. This AutoRad radiator's tubes are insanely tight together. I had to fab up some aluminum mounts for the electric fan because the long plastic doo-dads that you usually pass through the radiator to pull it tight won't even pass through!!!!
What does the 15" fan look like,some of the flexible fans,especially the aluminum fans flex too much and do a poor job of cooling. I use a 17" steel bladed fan and never have any heating issues on my sedan or the wagon. BTW,I don't have a shroud on ether car. HRP http://www.summitracing.com/parts/flx-1617/overview/
Autorad makes a nice unit. Have you talked to them? The tighter the radiator tubes are the more important a proper shroud becomes. Since the fan will draw from the areas that have the least resistance, it better be thru those " tubes that are insanely tight together" and not around the sides. A 17" fan is 30% larger than a 15" fan by area. So it will pull air over a 30% larger area of the radiator. Does it move more air, I'm sure it does but even if it moved less air but over more radiator surface the cooling capacity would be increased
Diameter of the fan is only one factor......others are number and pitch of blades. Another consideration is the width/height of the radiator........a fan overlapping on all sides is wasted blade length. A fan that does not reach the sides of the core in at least one plane is not going to be fully effective. That's why a shroud is often a good item to have installed for max effective cooling performance. Ray
I don't think they even make that radiator any longer. In addition to wanting to try out the 17" fan, I *do* need to fabricate an effective shroud. I considered getting the Walker WS-55A or the WS-60 where I can cut it to fit...no fab needed.
It's been a couple years, but Jim from Autorad built me a masterpiece of a radiator from a cardboard and tin mockup I sent him. He couldn't have been a more helpful person, a better businessman or a better craftsman. If you're having issues give him a call
If it only creeps up at idle then a shroud should take care of that without increasing the fan diameter.
Without a shroud, it's much easier for the fan to draw air in from the sides between the radiator and the fan, than to draw the air through the radiator - and air that doesn't pass through the radiator won't do you any good. Put a good shroud on it and you should be good.
I'm on it....going to have to fabricate a complete legit one, though. Based on positioning of the fan in my setup, and prefabbed ones being a bit pricey for me, I'm going to try and make one of aluminum and some wood forms, i think.
What does it creep up to? Had guys with SBC tell me they are getting hot. Asked them what hot was. They say 200#. If it is not puking it is not to hot. I use the fan HRP shows and never had any problem. I never liked a pusher fan in front.
I had overheating problems with a pusher electric fan. I switched it for a pull electric fan and my problems went away. I believe the fan was blocking airflow thru the radiator. Try taking off your pusher fan and run just the mechanical fan. See if your temp doesn't get better. It's free to try. Sent from my SM-N900P using Tapatalk
You have nailed the problem..AIR FLOW. You are not getting enough air at idle . Another radiator probably will not fix your heating issue. Maybe a radiator with more space between tubes will flow more air. I would go to a shroud first Remember your goal is to pull air through the radiator not from the sides. Please post the fix when you get it.
A very basic shroud would be a sheet metal "ring" around the fan. It doesn't make the fan pull air through the whole radiator, but it prevents it from drawing air in from the sides so it forces air through a portion of the radiator at least. Very simple, very basic, but still much better than nothing.
I found an aluminum tray that has the same dimensions as the core of my radiator, so I'm going to start with that. What you mentioned about the ring is something else I was figuring I would add on in case the depth needed to get to 1/2 the depth of the fan isn't there. Using the wood form and a mallet to flare it out was going to be my first option before that.
So, I think I've got it solved....*crossed fingers*. Even though I'd prefer a non-flex fan, I got a 17" one to replace the 15" one that was on there. I then modified my ghetto half-shroud to the new diameter and flared out the edges. I'm now holding steady at 195-200 on a hot SoCal day, in park. I'll finish out the shroud to be a full shroud and hopefully bring it down a bit from even that benchmark. I know that the centers of the fans are null zones for pull, but has anyone ever invented anything to bolt on that area to turn it into a draw?
I would do a shroud before I changed the fan. I use a fan like HRP when I run a mechanical fan and it pulls plenty of air. But like I said before I changed fans I would build a shroud and loose the damned pusher fan that cause more problems than they cure.
About the only time I ever used a pusher fan was for parade duty. Stick it in before you got staged , take it out when your done but after it cools of course. Works good for that. It really sucks to be sweating your ass off in a hot car and need to turn the heater on to help the engine drop a few degrees.
In SoCal, sitting in traffic idling is the name of the game...it's parade mode at least half of any drive, anywhere! I put the pusher back on, purely because I know guys out here who have a pusher or extra puller electric fan for the idling in traffic mess. Once I get the final shroud fabbed, I'll probably put two 5" pullers on the upper part of the shroud and pull the pusher off the front and see what happens. Heat here is a way of life.
Pusher fans impede air flow more than puller fans. Look at the surface area of the fan motor and the fan hub 'null' area....that is all in conflict with air flow.......even as the fan is running.....it is less efficient than a puller. Ray
I don't deny the principle behind it, but I ran it with the new setup, without the pusher, and it was headed towards 210 where it appeared it would stop. Putting the pusher on held it back to 195-200. I'll swap it out for the two smaller pullers once I get the final shroud done up.
Too True, Totaly Agree with "Tight tubes need a tight shroud" Three things involved with that thought. Ram Air Force, square area, and back pressure. Air is like electricity in that it takes the least path of resistance. Like smart or lazy people. Yuk-yuk There is also some boundary air problems when you look at numbers real close. Sent from my iPad using Tapatalk
There are some old threads on here concerning this, which cover a few points not touched on here. I built my own shroud for my 283 in my no-hood '33 & I've always run pretty hot (210+) as a general rule. But, it hasn't puked, so I could barely care. That being said, I've never never be struck in some long line on a 100 degree day. From reading about this whole thing over the years, I found out that I did two basic things wrong. (I swear one day I'll make the corrections.) First, the fan blades should be halfway in the shroud & halfway outside the shroud. Secondly, the four triangular corners outside the shroud should be blocked off. I'm just throwing this out so you can take it into consideration when you're building yours. Maybe you can call me Captain Obvious, but when you're doing things for the first time, not much is obvious.
I have two questions on this subject. Fleetside 66 what is the theory on blocking off the four corners of the radiator? And everyone that's running a steel bladed fan off of the water pump are you also using a fan clutch or just bolted to the pump with a spacer? Pat
1. Fab or buy a properly designed shroud, see here: http://www.route66hotrodhigh.com/FanShroud.html 2. Use the largest diameter fan possible 3. Use a steel blade fan with the most blade count, 7-9 blade if available, see here: 4. Use a quality thermo clutch fan if you have the room 5. Remove the electric blow-through electric fan that IS blocking air at speeds over 30 MPH. 6. Enjoy your Hot Rod.
Pat, I interpret the corner covers as part of the theory G-son spoke about in Post #9. Also, I'm just running my fan just bolted to the pump with a spacer. That's one of the things I have to do...install a shorter spacer so that my fan position is corrected.
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