cutting out back of cowl hood?

[jon_eds]

Got a new cowl hood and I want to open up the back to help move air in and out of the engine compartment. How much or little can u cut out the back of the cowl or cut a few holes with a 3" hole saw? If drilling holes is the route to go anybody found any trim rings to dress the holes up and maybe reinforce them?

 

[DanHall]

Cut the back out of mine following the contour of the hood leaving about 3/4" lip with a center section about1-1/2" wide for support. Then glued some flat expanded metal that I painted to match my trim. I used a marine grade adhesive to glue in the metal. Seems to work well.

 

[bronconut73]

It can cause overheating at highway speeds due to the high pressure at the base of the windshield. The air pressure there can overcome the force of the fan and the air flowing in the front through your rad.

 

[tatersalad]

Ditto what Bronconut said, I wish I had never done it, a better spot too open up would be on each side, a small BL helps and or those inner fender mods. I had a 75 that someone had bent the inner fender skirts outward back by the floorboards to achieve a little more flow.

 

[Desert Dweller]

I put a "reverse" scoop on my hood thinking it would help air flow. It lets air out up until 10 mph, at 11 mph it turns into cowl induction and air starts going back into the engine compartment. In the summer I block it off now.

 

[AZ73]

Just out of curiosity, I was planning on leaving the vents in the hood, but since I'm putting a BC A/C system in, I won't be using the air vent on the PS. I thought I would leave the vent in the hood open to let hot air out. Is that a mistake?

 

[jon_eds]

It can cause overheating at highway speeds due to the high pressure at the base of the windshield. The air pressure there can overcome the force of the fan and the air flowing in the front through your rad.

huh, I know air does funny things flowing around vehicles, never would have thought that.

 

[siderbox]

Chevy used this alot in the muscle cars.
Here's a few Chevy folks that give some more info on the subject.

http://forums.corvetteforum.com/fac...unction-does-a-cowl-induction-hood-serve.html
http://www.camaros.net/forums/archive/index.php/t-15796.html

 

[broncnaz]

huh, I know air does funny things flowing around vehicles, never would have thought that.

Thats where cowl induction became popular its not just a look even though most people do it for the look.

 

[SHX669]

Another Bronco " your results may vary".
We've been running a cowl inducted hood for 13 years - 2 with a HO 5.0L and 11 with a "HO" 351W - 6 years it was a daily Driver -Daily - and We've never had an over heating issue of any kind at any speed at any place. In fact this particular 351w seems to run a little cool.
We drilled 5 evenly spaced 2-1/2" holes with a holesaw [leaves some strength}
in the center ' high rise' part .
The fresh air vents in the hood we drilled 3 evenly spaced 1-1/4" holes.
SHX

 

[plumbdoctor]

^^^^, same here! never have had a problem with mine either

 

[u10072]

yea theres absolutely no cooling issues with holes in the back- and yes the 5 holes idea is a good way to keep the strength in the hood.

 

[73azbronco]

Agree, air going into or out of the cowl is good, if its going out, it takes hot air out, going in, cool air in. Biggest issue is what's your radiator doing, is it having issues directing the air to the right place, that's usually a shroud or core support seal issue.