Is there a good way to get underhood heat out without a cowl hood?

[MadmanMark]

Things are getting super hot under my stock hood. I have a cold air setup, so the carb is sealed to only get outside air, which helps the carb keep its tune but leaves nowhere for hot air to go. I have inner fenders without flaps, so there is some opening toward the tires, but the lid of my air cleaner could give you a burn with all the heat collecting up top.

Here are the options I've thought of:

1) Cut vents in the stock hood
2) Take off a section of the rubber seal at the back edge of the hood seal by the cowl and/or off the strip on the back of the hood
3) Get a cowl hood (I don't like this one since I don't want to lose the sleeper look)
4) Replace the metal lid on the air box with something non-metallic (to reduce heat to the carb)
5) Electric fans? (although my car has been telling me to stop adding electronics )
6) Some combination of these and others?
7) Live with it until it causes some sort of trouble

Anybody have any suggestions? Also, how hot is too hot?

[horsewidower]

Re: Is there a good way to get underhood heat out without a cowl hood?

1. yes
2. no, the base of the windshield is a high pressure area and air will actually enter there.
3. see 2
4. You should actually insulate the base.
5. What are they going to vent and to where.
6. yes
7. Holes are cheap.

What kind of car are we talking about?

[MadmanMark]

Re: Is there a good way to get underhood heat out without a cowl hood?

I'd post a pic, but I think I lost the host link I was using. It's a 69 chevelle, 427 sbc, th400 full manual/rev vb/tb, and 3.55 12 bolt. Not an SS, but with a real SS hood. The carb is well insulated from below with a holley heat shield under the carb and a fiberglass enclosure that takes air from a big hole I sawzalled in the firewall.

My hood has many battle scars. I was thinking about getting a SS replica fiberglass hood (VFN) and then cut out some rectangular areas to mount some vents. I think there's something that might work from an earlier model that has the vents on the sides of the 2 raised areas on the hood. It seems these things would let a lot of rain in, but I still have some checking to do.

[Bamfster]

Re: Is there a good way to get underhood heat out without a cowl hood?

Since your hood is already battle scarred, how about pressing a few rows of louvers into it to let out the heat? I have the same problem with my F250....it's getting louvers before summer.....

[CTX-SLPR]

Re: Is there a good way to get underhood heat out without a cowl hood?

Honestly... Functional L88 hood scoop would work the best as it would pull the air off the back of the radiator so what does get through shouldn't have much resistance to venting under the car. Otherwise.... fender vents, Z34 Baretta type hood grills with rain trays, or a stream of interupted air at the carb location to cool it.

[joe_rocket45]

Re: Is there a good way to get underhood heat out without a cowl hood?

I take it using a hole saw to cut through the firewall and into the cowl area is out of the question on a 69 Chevelle? :P

[SuperBuickGuy]

Re: Is there a good way to get underhood heat out without a cowl hood?

Do you have a front spoiler under the radiator? It's good for up to 20 degrees temp drop.... here's why - you need low pressure under the car to allow the heat to get out - when you're zinging along, the pressure in the engine compartment is lower then the air running under the car thus trapping the air....

If it's still not cool enough - wrap the heaters.

As far as the cowl point, that's not true - the air will blow out of the cowl unless it is sealed to the carb - otherwise, my car would be nice and cool when I have the vents open >
There are other problems with unsealed cowl scoops (or louvers) - any fluid leak goes directly to your windshield

[Bigbuds1]

Re: Is there a good way to get underhood heat out without a cowl hood?

Do you have a front spoiler under the radiator? It's good for up to 20 degrees temp drop.... here's why - you need low pressure under the car to allow the heat to get out - when you're zinging along, the pressure in the engine compartment is lower then the air running under the car thus trapping the air....

If it's still not cool enough - wrap the heaters.

I agree, I was thinking something like 3rd gen Camaro's have to create a low pressure area to draw in the outside air.

[MadmanMark]

Re: Is there a good way to get underhood heat out without a cowl hood?

Thanks for the replies.

Joe_rocket - the sawzall already cleared a 17x4 opening in the firewall to the cowl area to feed the air cleaner. I'm a little more nervous cutting into painted exterior stuff.

Buickguy - I have added a front spoiler. It did help bring underhood temps down a little bit and helped get me out of vapor lock territority.

Bamfster - Louvers sound like an interesting idea. Is there a cheap DIY louver device or does the hood need to go to a body shop? Is there an ideal place for them to go (like front/back/middle/sides)?

[IRONHEAD]

Re: Is there a good way to get underhood heat out without a cowl hood?

find a '85-88 t/a hood thats hit at a j/y and grab the four hood vents... two at the nose ,two at the hinge area//
also if you can find the room.. get some 2.5" flex steel exhaust pipe.. and put it up at the fire wall kick area.. one end pointing up into the engine area.. up against the fire wall.. the other end.. under the car.. with a angle cut..
this will suck the hot air out of the engine room as you drive..
you can use smaller pipe.. even 1.75" one on each side will work.. no fans.. ,no wire'n
just a little pipe

I might cheat and install catty truck fender vents ala t/a sytle..

[JeffMcKC]

Re: Is there a good way to get underhood heat out without a cowl hood?

You might do a A-B-A test most find the cold air package and the cowl hood air intake seal slows them down, the ones that work have many hours of work with air flow and wind speed tests to make them work correct where the air enters the carb correct

[Bamfster]

Re: Is there a good way to get underhood heat out without a cowl hood?

Bamfster - Louvers sound like an interesting idea. Is there a cheap DIY louver device or does the hood need to go to a body shop? Is there an ideal place for them to go (like front/back/middle/sides)?

Let me do some research....I know a few old time body guys....

[milner351]

Re: Is there a good way to get underhood heat out without a cowl hood?

as a test before replacing the hood - you could put shims / washers between the hood and the hinges to raise the rear of the hood up allowing a path for engine heat to get out - or depending on aerodynamics - allow cooler outside air to get in.

this would at least give you a real world idea of how much a cowl style scoop would help you.

[SuperBuickGuy]

Re: Is there a good way to get underhood heat out without a cowl hood?

To do louvers, you need to take the inner structure out of the hood. Get the punch (it's a 2 piece die) and a way of pushing it through the metal (like a press brake); or get a pittsburgh machine with the associated dies to make the holes.
Really, find a metal shop that does louvers - then pay them the buck or so per louver to have them do it because of you mess up, it looks terrible.

[MadmanMark]

Re: Is there a good way to get underhood heat out without a cowl hood?

Here's a pic of the engine setup:


I went to the cold air setup after running into problems keeping a tune (possibly due to the underhood heat problem + FL heat). It seemed fine for around town testing but went super rich during long drives. I did test the system with and without the cold air box a while ago with a 12-13sec 383 and found no performance difference.

My problem seems to be after it's shut down for a specific amount of time or getting stuck in slow traffic for long periods. I've been debating getting rid of the boat anchor hood before it gets another paint job (last one was in '89) and going fiberglass. The car is an original 6 cylinder and has the 250 badges but the SS wheels and hood. If I went fiberglass, I was leaning toward getting the same hood style, but this underhood heat issue has me thinking cowl.

I might try jacking up the back of the hood a bit to see if it helps any. I'm also going to bring along my ir thermometer to see how hot everything is getting under different conditions and do testing with the hood down and then up. I also have hood insulation that maybe should come out (although it might cook the paint :-\).