is there a fan shroud mod where you drill or cut holes in the area between the fans to allow more air flow?

 

I had opened up the areas below the fans in between any ribbing using a drill and air saw. It helps a little with air flow at speed. May reduce some front end lift at high speed. I purposely did not open any holes above the fans because without opening a hole in the hood at right behind the radiator the hot air will have no where go and simply increase lift.

 

That's what I was thinking because the fans stop working at about 35 mph. I'm wondering just how much can be cut without affecting the fans when at slow speed. Surely someone has information on this.

 

Personally I wouldnt do it as those shrouds have a purpose and that is to draw air through the radiator when the fans are on.Any holes you add will make it just that less efficient.Those engineers at times know their stuff!

 

I have seen on some OEM shrouds, and also the one on my street rod, where there are holes made such as you are suggesting but they are covered by thick rubber flaps that will open from the force of highway speed airflow. When you are slowed down or at rest and the fans turn on, the flaps will close back against the shroud and the fans will pull all the air through themselves with no air leaking where it shouldn't. The shroud made such a difference on my rod that no matter what the outside temp or vehicle speed, the car runs at 185 degrees with the a/c on or off, even at extended idling periods like cruising an event fairground.

 

Not a good idea. If you cut more holes in the fan support then when the fans are on you will pull air through the holes and not through the radiator. On early fan supports there were some extra holes in the support but they had flapper valves on them that closed when the fan started to run. The radiator support on my 97 had the holes and flaps but the support on my 03 did not have them.

By the way the lack of cooling at speed isn't due to a lack of airflow but to a lack of cooling surface in the radiator. There are some things that can be done at the front of the car to make sure all of the air that is supposed to go through the radiator actually gets to the radiator. If you are doing a lot of WOT runs at mid triple digit speeds you should make sure the center spoiler is locked into place by running some duct tape from the top of the spoiler to the spoiler support. Once speeds get to a certain point the spoiler which is designed to be bent backwards when it hits an object will be pushed backwards by the air pressure VS staying put and forcing the air through the radiator. Also check around the front of the A/C condensor where the shroud mounts to it. There should be some foam sealer between the two to keep air from escaping into the engine compartment. That foam blows out of the gap on a lot of cars that see triple digit speeds. Sometimes you can see it sticking out beside the shroud when you open the hood.

Bill

 

FWIW, after I made some openings as I described above the car did not run any hotter than before in stop and go traffic. If you are concerned you could try it and if you find your car gets warmer then install some thin rubber as mentioned above.
I've since replaced my radiator (was dewitts w/oil cooler) for a circle track double pass that I custom mounted and used a laminova oil cooler in the lower hose. Rather than re-install the clumsy factory fans I installed a single 16" spal with no shroud. The fan itself is completely sealed against the core, but obviously the rest of the core will rely on airflow when the car is moving. The idea is to free up the airflow at speed as much as possible. Same reason for laminova heat exchanger in lower hose as opposed to air/oil cooler stacked with radiator and a/c condenser. I have not finished the car so I cannot say if the fan will be enough in traffic or not, but should know in the next couple months. I chose the highest flowing spal 16" that is rated for continous duty and sealed for wet use.

 

I finally got around to finishing this up and fired the car yesterday. Not drivable yet, but I ran it for about 15min or so sitting in the garage and the cooling system seemed to work well. It was about 60 degrees outside so I'm sure there will be more stress on the system in 100 degree still traffic, but so far so good. The dual pass works REALLY well. I didn't write down the actual numbers, but there was about a 60 degree difference between the first and second pass. If placing my hand on the upper core it was definately hot near the radiator inlet and at the outlet on the bottom the core was actually cool. I think it was something like 75degrees when I shot it with a temp gun. There was even a cooling effect in the tank as the water dropped down from the top core. Not to mention the laminova acts like a heat sink further shedding heat.
For the fan I simply made a jumper harness to plug into fan 2 plug and my single runs off the fan one plug. It is currently programed to turn on at about 195 (as best I could tell from my display) and as soon as it kicked on the temp immediately dropped and the fan turned off at about 190. It flows a very noticable amount of air. I could actually feel cool air flow into the opening under the bumper. Didn't think I would with only one fan and the condenser as well as thicker radiator in the way.
Once I get the car drivable in the next couple months I'll know better, but so far it all works even better than I expected.
I've also adding some openings in the hood to promote heat extraction from the radiator.

 

Hey track boss, did you ever get your car on the road? My last trip to the track I was having to take a couple of slow laps in the middle of the session to get my water temps down so I'm looking at options to increase airflow through my rad.

 

x2!

 

I agree, to a point, but if you add a massive 16" fan to the setup I would think you'd be able to make up the difference.

In my situation I'm not as stressed about that either since it's not a daily driver and therefore spends very little time idling.