Sizing a minimum size grill opening.

[67-ls1]

I am looking at closing up some of the grill in my car for better aero dynamics.
Behind my radiator is a 19" diameter round opening in the fan shroud. Less when you consider the round hub of the electric fan.
If my grill is sealed to the front side of the radiator, is there any reason I need more opening in the center of the grill?
Thanks,
Dennis

[dirtydave]

I would block 80% and see if it over heats. then 60% then 40% and see where shes happy. you need a accurate water temp gauge

my car is happy with 95% in winter 70% in the summer.

[ChazInMT]

Block from the outside in and the top down. You want the opening to be as low and centered as possible for the best aero gain. Cooling systems are designed for a car fully loaded, going up a mountain, with a tailwind, on a 120 degree day, and behind a semi truck.



Sorry if I offend, it is really not my intention, but in looking at the 67 Chevy, the grill area is sloping the wrong way for proper aero dynamics. We want as much of the air to go over the top of the car as possible, not under. It isn't the absolute worst aero front end you could design, but it's close.

[67-ls1]

No offense taken. Yeah I know, it sucks, but that what I have to work with, so...
Mine is a 66, so maybe slightly better as my grill is slightly less sloped.
I plan on blocking the entire grill area and taking air in from the center of an air dam I am going to add.
That was the purpose of my question. A "%" type answer does not really apply since I am going to block 100% of the original grill area and need to know what open area to add in the air dam.

[aerohead]

I'm gonna try for a link to the original 1984 CAR and DRIVER article on streamlining with the Pinto.You can see what they did.
http://ecomodder.com/forum/showthrea...25-a-1186.html

[2000mc]

Originally Posted by 67-ls1

19" diameter round opening in the fan shroud. This is approx. 60 sq. in. (19x3.14=59.66)

8.5 x 8.5 x 3.14 = 226.865 sq in

Originally Posted by 67-ls1

I plan on blocking the entire grill area and taking air in from the center of an air dam I am going to add.
That was the purpose of my question. A "%" type answer does not really apply since I am going to block 100% of the original grill area and need to know what open area to add in the air dam.

are you planning to add an air dam directly below the radiator? is there an oem air dam? open area, as in size of the air dam? open area, as in gap at the center of the air dam out in front of the radiator re directing air up behind the grill block?

even though im doing this myself, im not convinced its better than a more conventional small grill opening. however i think the difference would be small if both are sized right

my own car has the grill completely blocked, oe airdam directly under the radiator, i have added an air dam at the front edge of the bumper. add on air dam is maybe 2" tall (paver edging). i first added it all the way across, couldn't keep the temps under control. with the center cut out 6" wide, and angling the cut out to 12" wide at the bottom, the car would eventually over heat (testing at 70degF) even at low loads, and any speed. with the gap cut 12" wide top and bottom i had no trouble keeping the temps under control ( eventually found the limit, 92degF, a/c on, 72 mph would maintain, 75mph would push temps up). i think the difference the last cut made was beyond the extra 6 square inches i removed. i think the angled bits might have been pushing the air under the oe air dam, giving me little more than if i had the gap cut 6" top and bottom.

i dont think there's a set formula for the openings needed. if my front end was flatter, maybe i wouldnt need as big of an opening, or maybe the air would shoot down to the ground and completely skip over the oe air dam. my grill is blocked from behind, and the plastic i used curls up and around, helping draw air up towards the top of the radiator, not unlike how vettes were done, with out that, i might need a larger opening. if the oe air dam was taller, i might get by with a smaller gap. whether or not someone has a/c, p/s, lrr tires, side mirrors, old auto trans w/o lockup converter...

[67-ls1]

Given that my car does not have the most aero grill/front end, where (vertically) is the best location for the cooling air intake?
Up high just below the transition to the hood or down low at or in the air dam to be added?
Also, would it be better to have the opening shorter and wider or roller and thinner?
Dennis

[spacemanspif]

The air dam needs to be placed directly under the radiator, so basically right on the core support. With 100% sealed front end you'll also want to make up a "skid plate" or belly pan under the nose of the car to reduce turbulence and control the air a little better. Start your design where the belly pan seals the entire area from the very front of the car back to the air dam. Then cut a hole in the pan that is maybe 18" wide and 6" deep. That hole will be where your cooling flow comes from and the rest of the pan and dam will encourage the air to exit the car off to the sides. The dam should be as wide as the car if possible and do double duty blocking air in front of the tires. You might want to consider creating a tunnel or channel in conjunction with the core support so that all the air coming into the engine compartment HAS to cross the radiator. Since air will take the path of least resistance there is a good chance that without the channel most of the air will flow around the radiator and just cause more turbulence.

[2000mc]

i don't think this is neccisarily optimal, and maybe more appearance based, but if it was mine I think I would try to make an air dam flush with the front bumper, no openings for air. Close off around any other openings in the front ( in and around bumper, edges of grill, headlights). Then I would just work with the stock grill opening. Start by closing in from the sides, untill I got down to about a foot wide opening. Then start closing that space from the top down. Also like spacemanspif was saying, close off around all sides of the radiator, to make sure all the air that comes through your grill opening, goes through the radiator.

[67-ls1]

My plan is to add an air dam to the bumper, shaped similar and faded back towards the front wheels.i plan on adding a panel from the bumper back to the core support to seal air that goes through whatever opening do that it cannot then go under the car.
I will also seal up the core support so that air that does go through the grill opening must go through the radiator. It's pretty good now, but not perfect.
For blocking the grill, I will use clear plexi glass attached to the back side of the grill itself.