A few weeks ago, I was bored at home and wanted to tinker with the truck. Talk of summer 4x4 trips was in my mind, and I got to thinking about cooling solutions. I always liked the look of hood vents, but being a 'baller on a budget," I decided to make mine from a Home Depot air return grill intended for use in the home.

A fellow ExPo forum user and I recently ran a trail that had a lot of fairly steep climbing, in fairly warm weather, so I got a chance to test out the vent mod.

Part way up, his A/T temp gauge lit up, so we shut down for a few minutes to let his truck cool down. My light hadn't come on. Then for fun, I held my hand in front of the grill of his '98 SR...the radiant heat was very strong. I walked over to my truck, and did the same test...and it wasn't nearly as hot. There just wasn't as much heat collecting in the engine bay. It was a lot cooler under the hood.

We are both in stock-engine Monteros, his was on 31's and mine on 33's...on the same trail, at the same time. Trans fluid was at about the same level and cleanliness on both trucks, and they have the same radiators, fans, oil and trans coolers. So all I can think is that the hood vent and hinge-prop mods kept everything, including the transmission, measurably cooler. If you don't mind hacking your rigs, I highly recommend it. <img src="/forums/images/graemlins/kewl.gif" alt="" />

That is SO freakin' ghetto, but it's cool. I like it.

John B.

That should work great for slow moving on trails, but I'd be careful to watch your temps when you're driving uphill at highway speeds. The area in front of the windshield is a high pressure area and opening the back of the hood like that means that air will probably be flowing into the engine compartment through that opening, not out of it. Having higher pressure under the hood could potentially reduce the airflow through the radiator, reducing your cooling.

Kudos to you for trying it out, I don't know that anyone else has done anything like that before. Obviously it's helping to vent underhood heat at slow speeds - I'd love to see some airflow testing to see what it does at higher speeds also. You could tape some pieces of yarn to the rear underside of the hood to see what direction and strength the airflow is at highway speeds.

I'll bet if someone worked at it they could make a weighted louver. When travelling over xxx MPH the wind catches the grid/louver and closes the air flow but at slow speeds a bottom weighted louver opens allowing ventilation under low - crawl speeds.

No affiliation with products below, but there are tech alternatives to ghetto.

Cooling:
Electric Fan Engineering website


Engineered louvers:
Hood Louvers.com



I've seen hot-rodded cars...like an Austin-Healey 100 sporting a Chevy 383 with louvered hood and 12V compact cooling fans for engine bay heat extraction.

I like it! If you had another hood and an accurate temp gauge you could very easily determine whether it had a negative Impact on highway engine temps, eh?

I used an 80s Chrysler hood vent on my 3rd gen I, in the interest of reducing underhood temps by the battery. I didn't notice any increase in running temps, but this is based on the stock gauge, so I can't say for sure... I agree though, a louvre might give you the best of both worlds.

Glad you guys like it!

I've done the tuft testing on other cars; both the Volvo (big-ish turbo, over 400 wheel HP) and the Bug (2275cc's) are vented with good, measurable results. So I wanted to go a step further on the Montero since there was more real estate on the hood to play with! <img src="/forums/images/graemlins/wink.gif" alt="" />

In someone else's words, this is the concept I was working with: the nose of the car, and the base of the windshield, are higher pressure. The center of the hood is lower pressure. The "prop" at the back of the hood creates a gap at the fender which extends more than half way down to the nose of the car. So while the base of the windshield and the nose are high pressure, the center is canceled out - and this is where the heat will gravitate out the vent and the side gaps. I will do some "real" testing (with numbers) when I can, but I can tell you I have seen enough difference already...and once I install the extra oil and trans coolers I have sitting here, that would more than offset any situation where the vent/gaps might not work as efficiently. It might run TOO cold, actually, so I will have to wait until I can monitor temperatures a little more accurately!



I would have done "pretty" louvers, but I neglected to mention...this truck was totaled when I bought it, and it already had a mismatched black hood. I don't have the time, money or patience to make it look like an OEM fitment, so this was just fine for my intents, purposes, and budget...the grill was $14.97, and the paint was $3.97. Grand total was well under $40 and under 2 hours of work. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Definitely a high pressure area at the base of the windshield. That's how "cowl induction" worked. Basically, the pressurized air at the base of the windshield would be given someplace to go - into the engine bay. Properly done, the intakes on such vehicles were isolated from the rest of the engine bay to maximize the intake charge, but that's definitely how it worked.

That said, if the louvers on that vent panel are raised above flush and open toward the windshield - that is, they are not "scooping" toward the front of the truck - at higher speeds, the airflow across them would create a tiny low pressure area just behind each louver, effectively drawing heat out. A smaller, simpler version of what goes on with the RRE hood vent, popular in the DSM community.

It would be cool to make it all pretty like that hood you posted...but damn, that costs money. lol!

I live local to Road Race Engineering, been in there several times for work over the last 15 years or so. Had a few friends with DSM's way back when. They were in Huntington Beach originally (next to The SHO Shop...another neat place).

From the reading I've done, the most effective place to locate a hood vent is right behind the radiator, like the location of the forward hood vent in the DSM hood photo that Brian posted above. The vent opens into the low pressure area in the center of the hood and allows the hot air that has just passed through the radiator to exit the engine compartment. Hood vents elsewhere in the hood are usually not effective and often create more airflow problems than they fix. I'm glad to see you did some research before you cut random holes in your hood. <img src="/forums/images/graemlins/smile.gif" alt="" />