Hood Vents VS. Hood spacers? What are you running?

[Stumpalump]

I worked on my hood today and it came out nice so I thought I'd pass it on.
I spaced the hood a ways back with longer bolts and washers but never liked the looks or how little air space it created. Today riped the rear hood gasket off and beat down the metal gasket flange the rest of the way down to let more air thru. Still not much air so I opened the hood and put a 2"X6" dead center of the rear of the hood and balanced it on the cowl. As I slowly let the hood down it bowed the hood up to increase air flow. Yea, you can crack the fiberglass cowl so I went easy. This opened up the gap real nice and looks stock. The side profile still looked goofy with the sides of the hood jacked up so I stood on the nerf bars and leaned down hard on the rear corners. This bowed the rear corners down and closed the goffy gap about half of what I had. Now that it lets a lot of air thru and looks half decent I think it's a great cheap way to let it breath.

 

[Mudweiserjeep]

I worked on my hood today and it came out nice so I thought I'd pass it on.
I spaced the hood a ways back with longer bolts and washers but never liked the looks or how little air space it created. Today riped the rear hood gasket off and beat down the metal gasket flange the rest of the way down to let more air thru. Still not much air so I opened the hood and put a 2"X6" dead center of the rear of the hood and balanced it on the cowl. As I slowly let the hood down it bowed the hood up to increase air flow. Yea, you can crack the fiberglass cowl so I went easy. This opened up the gap real nice and looks stock. The side profile still looked goofy with the sides of the hood jacked up so I stood on the nerf bars and leaned down hard on the rear corners. This bowed the rear corners down and closed the goffy gap about half of what I had. Now that it lets a lot of air thru and looks half decent I think it's a great cheap way to let it breath.

Can you post some pictures of you hood? Sounds good.

 

[ddeadserious]

here are the hood vents I used, they were CAD designed and custom laser cut by the previous owner of my previous Jeep.

At idle, it sit a little under 210, when moving, it sits a little over 210. It helps a little, I can see heat coming out of it. My next cooling mod will be to replace the clutch fan with an electric fan on a switch in addition to the stock aux. fan.

 

[Tim_MN]

Hood vents are from a Pontiac SunBird Turbo GT (1985 to 1995) They are aluminum with a powder coat finish and have a plastic gasket that you can use for a template to drill the mounting holes. The aluminum is soft and the vents can be bent and shaped to fit the curve of the hood. They are about 8 inches wide by 9 inches long which is smaller than LeBaron vents so you have lots of room to cut and drill and stay away from the under-hood braces.

Before the vents were installed the temp guage always read about the width of the needle above the 210* mark. With the vents installed it now runs one needle width below the 210* mark and the aux electric fan runs less often and for a shorter period of time.

 

[rstarch345]

Aw come on! Lets talk real vents, not those fly catchers you're showing.

 

[XJLafonda]

Would mounting a small fan UNDERNEATH the vents to pull hot air, or push cool air over the engine work? I don't want to mount a fan to where it's noticeable, but I like how vents look, and they do open the hood up a bit, so would mounting a fan under the vents and out of sight work?

 

[ckowennos]

I am running my recently installed lebarron hood vents. I have had no problems so far and also only minimal improvment in the temperature guage; but having them can't hurt too much. I have been thinking about fabing some sheet metal covers with magnets on them to keep rain out while driving.

http://www.jeepforum.com/forum/showthread.php?t=423018

 

[TIMEBOMB]

I put a 160 degree thermostat in mine...it helped alot! I'm thinking about spacing the hood up also for cooler underhood temps.

 

[avnsteve]

I call BS on any claim that venting the engine bay in any way reflects on your temp gauge in the cabin. the only benefit you could get from venting the engine bay is longer life from plastic and rubber parts in the bay. A properly functioning cooling system will not be affected by any outside air, unless it's a significant difference like winter vs summer, and even then not always. vents are cool, but please, they are not going to change the temp of your engine coolant on the gauge...

 

[MisterFubar]

I call BS on any claim that venting the engine bay in any way reflects on your temp gauge in the cabin. the only benefit you could get from venting the engine bay is longer life from plastic and rubber parts in the bay. A properly functioning cooling system will not be affected by any outside air, unless it's a significant difference like winter vs summer, and even then not always. vents are cool, but please, they are not going to change the temp of your engine coolant on the gauge...

X2

I want to vent mine anyway in hopes that it will help with my Intake Air temp. I've been driving around with the Scangauge II hooked up and around town my intake temps get as high 160-170, and on the highway it's usually at least 40 degrees above ambient. I know it won't make a huge difference but the cooler air I can suck in the better.

 

[1bolt]

I did a cowl hood write up in the mod tech forum last year and I just completed a sealed cold air intake box. I had been running with the filter routed to the passenger side close to the cowl opening, but not heat shielded or sealed. While I was finishing it I ran some tests. I duct taped the cowl closed, and used an intake air temp gauge and a laser thermometer. I ran three identical runs the first with the cowl taped closed, then open with the filter near the cowl and the last open with the filter newly sealed to the cowl with no under hood air getting into the filter. I'm going to post a write up of it in the mods forum as soon as I get the pics of the air box I fab'ed sorted out. As a teaser, under hood averaged temps droped during each test by about 10 degrees, with the outside of the hood alone going from 125 degrees to 110 to 98 with the air box sealed.. The cooler intake charge (and thus combustion temps) has a very noticable effect on engine temps.

There's certainly truth to the idea that the cooling system has the most effect, but the Cherokee has a big hot engine with it's intake manifold heated by the exhuast manifold, and not the best cooling to begin with. So a Cowl or vents can definitely help the cooling system do it's job a little more easilly. If only by letting some of the radiant heat off the Exhaust escape or be sucked down away from the intake manifold. If you reduce the air temp in the combustion chamber you reduce the overall engine temp pretty effectively.

To MisterFubar: You can definitely cool off your intake charge with cowl induction. With my cowl opening sealed and the filter breathing under hood air (on the cooler passenger side of engine), the intake charge AVERAGED 60 degrees hotter than Ambient at sustained HIGHWAY SPEEDS... It was hotter at slower speeds. However with my Intake sealed to the cowl opening I got intake temps 2 to 6 degrees above ambient outside air temps. figuring using the drag racing rule of thumb (where 10 degrees equals 1% HP gain or loss) that's about 6% HP increase across the board.

TO those of you worried about water... I have been running mine daily for a year or so now and not a drop of rain gets in, even heavy rains have never gotten the filter moist. And I have nothing special to divert water I don't even have a mesh grill or screen across the opening. So stop worrying.

 

[Blue XJ]

I did neither, I went with the hood scoop instead. I just took a second hood and cut the center section out and bent it to make the size scoop I wanted. I think I it turned out pretty good.

 

[MisterFubar]

To MisterFubar: You can definitely cool off your intake charge with cowl induction. With my cowl opening sealed and the filter breathing under hood air (on the cooler passenger side of engine), the intake charge AVERAGED 60 degrees hotter than Ambient at sustained HIGHWAY SPEEDS... It was hotter at slower speeds. However with my Intake sealed to the cowl opening I got intake temps 2 to 6 degrees above ambient outside air temps. figuring using the drag racing rule of thumb (where 10 degrees equals 1% HP gain or loss) that's about 6% HP increase across the board.

I will probably end up going back to a stock airbox(I bought it with a Volant on it) and a Snorkel. The snorkels are a little overkill on an XJ, but I think they look good and it will give me the cooler intake charge I'm looking for. I still want to vent the hood or put a cowl hood on to extend the life of all the rubber and plastic under the hood.

 

[TIMEBOMB]

Well...here at HEDMAN HEDDERS RACE DIVISION in Atlanta, we test...not guess. I do have a 160 degree thermostat and a manual override switch so that I can run my fan when needed. This past weekend at WINDROCK mountain in Tennessee, we put it to the test. With the A/C on, in 4 wheel low, hauling 4 fat @$$e$ up the mountain, my temp got up to nearly 200 degress...coming back off the mountain, it dropped nearly to 160 degrees. Riding 25 mph on normal roads, under normal conditions, the temp barely got above 160 degrees, when it did average around 185 degrees. I elavated the rear of my hood only 1 inch by using a piece of 1 inch aluminum box tubing. Piece of cake! The 160 degree thermostat played a major factor in this test.

click to veiw: http://good-times.webshots.com/album/559902333qgKmMM?vhost=good-times

 

[Mudweiserjeep]

Does the jeep run well with the 160* thermostat........I would think that the engine should run warmer since the stock thermostat is what....185*? Good info tho....thanks

 

[TIMEBOMB]

Heck, it's a six banger...I couldn't tell any difference in performance! The A/C seemed to be a little colder...it will freeze your @$$ off!:cheers:

 

[ROBZ95Xj]

Does the jeep run well with the 160* thermostat........I would think that the engine should run warmer since the stock thermostat is what....185*? Good info tho....thanks

i ran a 160 stat in my 95, the only diffrence is that i lost 2-3mpg and it would not warm up at all in the winter, and it still over heated on the trails, i found the culprit was a bad radiator

 

[1bolt]

The long term effects of running way too cool (and 160 is WAY too cool) are Cooler oil temps which means: increased ring wear, increased cylinder wall wear, increased bearing wear on all engine bearings, lower horse power and torque, MPG will drop dramatically as your ECU will never get out of open loop mode, so you will in all likelihood carbon up your engine badly... but of course you might just stretch your rods out, egg shape a piston or bore before the carbon becomes a problem, because you are in effect driving an engine that it permanently not warmed up all the way.

In short 160 degree Thremostat = very bad idea

 

[MisterFubar]

MPG will drop dramatically as your ECU will never get out of open loop mode

I agree with everything you said except this statement. With the heated oxygen sensors this isn't really an issue. I've been monitoring what state mine is in and it's normally in closed loop before the coolant temps reach 100.

Even so, running an engine too cool is bad. I don't think I'd want mine running much lower than 185 or so.

 

[magnum CJ]

I am currently in the middle of this debacle myself. here is what I've found so far with a 4.6L stroker.

first of all, my timing is off causing what I believe to be a lions share of the heating problems. 20 degrees before TDC. for a stroker that already generates too much heat, this is a kicker. I put the hood vents in from a grand prix. mounted towards the rear of the hood and to the outside (I got pics if I can ever find them) they seemed to work better there in that I got lower under hood temps (by "feel" no measurements) and the rain drips harmlessly thru and not on anything important. they did nothing for engine temps however. one theory is that being placed at the rear of the hood draws all the hot air from the radiator past the engine helping it to retain it's heat. if they were mounted at the front of the hood the air could conceivably leave the compartment before ever touching the engine. again, theory and I didn't like the way it looked.

secondly, I ditched the manual fan and went dual electric. found a good amount of extra power out of the engine, a mile or two better mpg, and way better cooling power. an electric fan and override switch is number one in my book.

went with 3 core all metal radiator. started off great, and went downhill steadily over time. to get three cores the cores are smaller and I found them to plug up far easier. an all aluminum with large cores would be great I think, but I'm not paying over 500 for one.

went to a robert shaw 180 degree thermostat at same time as new radiator and temps dropped way low. worked good for awhile, but then I put a regular 195 back in hoping that warmer temps might affect fuel efficiency. it didn't. but I did start having temp probs again. I just had a recent meltdown of temps that I couldn't get rid of with the obstructed radiator and sticking thermostat so I flushed radiator and put my 180 robert shaw one back in and I'm back down to super cool temps. I got a 195 robert shaw high flow thermostat on order that I might try in it cause it gets mighty cold in the winter.