Hood Scoops?

[porkchop]

As many of you know, I have just added a hood scoop. You can see the pics here http://www.ifsja.org/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic&f=3&t=004642 Well during the posting there is talk of how the front hood scoop works compared to a rear facing scoop. Does anyone have any knowledge on this? Wether it causes turbalance as the air coming in forward and then the air being channeled in through the top meet. I have not seen any ill effects. All I have seen so far is a cooler engine. I am not going to take it off I am just curious as how my engine is being effected.

I am also going to make a slight mod to it this weekend. I will post some new pics when done.

I will also get some pictures of how it is attached when done also.

[irbob]

So you have noticed a cooler engine ha? Hmmm i do like the way the aft ones look but I better tread lightly on this one. I have a lot to do yet B4 Ouray and a scoop may be at the bottom of the list.

LIST:
Home made F/R bumpers
winch
rear locker
Rusty's 6" springs
rock sliders
custom door panels
more speakers
tint windows
pin stripe/molding
sip tires
and other stuff

[oldyellowwagoneer]

I cant run a hood scoop as we have many deep water holes and water washes over the hood quite frequently when we drop into them. I sure could have used one when I lived in nevada especialy the cooling benefits. The main difference as i understand it is that the rearmounted hood scoop helps pull air into the engine at high speeds and the front mounted scoop rams the air into the engine, especially helpful for big motors to get all the air they can use.Both offer a cooler denser air mixture that helps increase power. DENNIS

[nfroio]

What you need to find is a site that lists the differences between Cowl Induction and Ram Air induction, and the pros and cons of both... I will look around, but, most search engines are just pulling up sites that sell either.. sigh..

[porkchop]

That's what I am getting when I do a search also.

[oddfire]

I will be mounting a scoop on my cherokee w/401 shortly. I will be mounting it with the opening facing the windshield. I'm not too worried about getting more air into the engine compartment, but rather another path for hot air to escape. I've had a similar setup on my CJ w/225 and electric aux. fan and done many slow motion crawls over the rubicon in 80* weather without ever coming close to overheating. Hey Pork Chop, how do you like the durabak paint job so far? Is it holding up well? how bout washing off mud, does it stick more?....your jeep rocks......phil

[porkchop]

WHy did you mount it towards the windshield? where did you ge the info from?

I love the paint job!!!!! It is holding up great. The mud comes off real easy, when ever I can find some. With the rough surface the mud can not get a good hold on the paint. so it just comes right off :D .

[NYC]

I put a scoop on my CJ (built 360, stock radiator) because I needed additional cooling... I had too much power.

I cut a 9" hole in the hood and covered it with a forward facing (home-made) scoop.

I put an electric fan (from a Honda Civic) on the underside - pulling air out of the engine compartment. The fan was wired with a toggle switch on the dashboard - no thermostat (on the fan)

On the road, I left the fan OFF. The blades would freewheel backwards and allow air into the engine compartment.

On the trail, I turned it ON. This pulled air out of the engine compartment (Standing at the front bumper, the "wind" from the fan would part your hair... with hot air.) This had to create negative pressure and allow more air to be pulled through the radiator, in addition to dropping temp's under the hood.

Overall, the temp dropped 3-5 degrees on my mechanincal gauge.
And it looked badass :D

[Ridgbak]

--Good looking AND functional too...
--I'm not sure how a hood scoop would look on a stock machine like my '86.
--What I'd really like to do is have my hood louvered along both edges, on either side of the center 'hump'. Anybody seen this? It looks like gills, about 3/8s' of an inch high, and 1" apart.
--I've seen it a few times, but I don't know what it's called, or who might do that kind of work.
--These I would face towards the windshield , to draw air out while moving.
--Most of the ram-air scoops I've seen have a mechanical dam that can cut off air-flow. What happens in a downpour? (not that I've seen a downpour for over a year) :D

[porkchop]

George Andrews up in Phoenix has his hood louvered. He is running a 454 in it! If you go to the memembers rigs you can find his. It is an orange Cherokee.

I have not seen a down pur in a long time. I am making a plug for it as wee speak.

[82wagonlimtd]

Has anyone tried a "shaker" type hood scoop?? the hood seems like it will allow it being that there are no big cross pieces in the way...

maybe something off of an old Trans Am or maybe even an old Mustang (if you wanna spend the money).

I always liked the way they moved with the engine....just looked so cool.

Andy

[oddfire]

Porkchop, I have no scientific reasoning for the way that I mounted the scoop, more of a personal therory. And like NYC my aux. fan was used only offroad, when switched on you could feel the hot air blasting out of the scoop opening. My therory, for what it's worth is that hot air rises to pool in the scoop and the aux. fan pushes it out. works for me.....seeya in Ouray...phil

[irbob]

No one seems to worry about a down pour with that big ol grill out there. The hole in a scoop is much smaller...Just food for thought. :rolleyes:

[Tad]

Ridgbak, here in swamp cooler land it would seem we would have at least several AC/heating fabricators who could louver a hood. They make custom/replacement frames for coolers all the time.

[Ridgbak]

--Thanks T, that's a good clue. And it's exactly the sized louvers I was thinking about.
--It just occured to me that a re-paint would be needed too...

[porkchop]

I will be making a big change to my scoop this weekend. I just wanted to give all interested parties a heads up. When I get done I will post some pics. I am going to get my site back up hopefully tonight.

[Dive 30]

The biggest concerns (I have discussed with a buddy of mine who races Indy lites) with an induced vs. a forced induction type scoop is the 'ram air' effects and foul weather. A cowl induction type scoop pushes cold air into the engine compartment off of the vortex formed at the windshield, the same air pocket the heating/ac system is fed from. Thus, all the bugs/rain/snow/sleet/dust/whatever is naturally circulated out (to an extent) thus giving the benefits of the cold air without the risk, you get the same thing but in a lesser volume behind your headlights.

A forced induction does just that, forces air through the engine compartment. Much better temp wise, but you get all the outside stuff that goes with it. The other thing is, that most carbs (if you are running an open element) are not designed for pre-stage forced induction. Edelbrock specifically states in the literature for the 1400 series carbs that they are not to be used with forced induction systems. You just get too lean at even moderate speeds. I've got a set of the Lund Eclipse hood scoops (yeah the twin ones from Summit) that I want to face forward and have open to the hood for cooling and will put a snorkel on when I get my TBI done, but with the open element I'm running now, I'm afraid I would run too lean at highway speeds (though I'd probably see an increase in power and efficiency!)

Maybe the carb guys know what carbs work for forced induction (like a Q-jet maybe?), I'm not up enough on carbs to know how to make a ram-air work for those. For a EFI system, you have to up the injectors usually and re-program the computer.

This is a link to US Body (http://www.usbody.com/WhereQualityComesFirst.htm). They offer pre-fabbed cowlinduction hoods for our rigs. Kind of pricey though.

I hope that helps

Phil

[Jerk]

phil is correct, no air weighted secondary valved 4 v carb is supposed to be open to the airstream, as in, it should be covered. also the reverse versus ram air scoop subject he nailed.
When I had a holley 4v on my 401, I built an airbox out of aluminum and (you'll laugh, but)- Dryer hose as well as custom built air funnels and bug screens that ran from both inboard "headlight" holes in the face panel to the airbox. I never really noticed any performance increases with it, but it seemed to allow for somewhat cooler air into the box and therfore into the carb. I also thought about a hood scoop, but as phil notes, the edelbrock I have now, won't allow it. hood louvers are an absolute boon if you run in hot arid climates, my problem is, we get snow/rain 7 months of the year and I don't really need the extra cooling in the summer as my 3 core radiator works pretty dang well. as of now, I have off road lights behind the black bug screens in the inboard headlight holes and no hood/intake mods. BTW, ever seen a 70s cowel induction trans am that gets parked under a tree in the fall? can you say "Its a veritable forest in there!"? no kidding, leaves and bugs galore fill the screen and thus the air is blocked off from the intake. just seems like more "pre flight inspection" time to me...even though scoops just look cool! :D Triumph tr-7s and 8s had hood louvers, so it may be possible to check one of those out, or any other hood with louvers, i can just think of the trs of hand, and see how they did it.

[porkchop]

I have not noticed any performance changes with the hood scoop and my edelbrock carb. I was looking on the site and I cannot find where it says not to use ram air. I will have to check the book. Plus the air is not really "ram" air so to speak. Where the scoop is located and the size of it the air gets pushed down on top of the air cleaner not really into it. If it does cause it to run lean then I will just have to rejet and set the screws some. It is not like I am going 90 down the highway :D . Thanks for the info.

[Jerk]

basically, it just says the air-weighted secondary valves are not to be exposed to the airsrteam, as in pressured, since, that will mean the secondaries may be open all the time, and I surmise, problems like over richness or maybe even w.o.t. symptoms at higher speeds., you know, since the only thing keeping the engine from revving full bore is the "throttle" ie- the constriction of air way or air flow, is closed by a spring and lack of pressure on the go pedal! :D so if the secondaries "sense" air pressure and open like they should on there own due to too much air flow, they may actually over accelerate the engine...? I'm not sure, but it makes sense. I think you have to have the primaries open quite a ways in order for the secondaries to be mechanically unlocked though, I haven't really played with it to much. maybe the primes and seconds are matched so that as far as the primes are opened, they allow the secondaries to be opened the same amount? I'd go out and check but I'm lazy. ;) - laters. anyway, its in the paperwork with the carb. that's where I found it.

[Joe J-Truck]

I run a scoop on my 67 tempest for several reasons. The engine is a built poncho 400 with headers that produces alot of underhood heat. A cool air charge to the carb is essential for a high performance mill. The colder air is denser and more fuel and oxygen is actually be atomized in the air/fuel mixture going into the combustion chamber. Denser air/fuel mixture = bigger bang in the bore = more power. I stacked 2 1" spacers on top of the perfomer intake to get the carb up to where the air filter is actually sticking through the hood inside the scoop. I cut the hole beneath the scoop carefully to match the filter shape as closely as possible. I wanted to have all the air going in the carb coming from the outside, thus keeping the fuel charge cool.
I also wanted to create a "ram-air" effect at speed to force as much air into the cylinders as possible. More air stuffed into engine = denser air-fuel mixture = more power.
I'm using an edelbrock pro-flo filter, which I do believe is an open element type. Its true that more dust etc. gets in the filter, but this one is washable and reusable, and the maintainance is an easy chore that I don't mind doing periodically.
The addition of a forward facing scoop made a dramatic increase in performance and drivability, especially in the heat of NM summers, where tempuratures can easily be 100+ degrees. I can only guess how hot it gets under hood when I'm driving the car hard and fast and the headers are glowing red-hot!
In the event of a downpour, I just leave the muscle in the garage and drive my jeep. The M&H racemaster slicks on the rear of the Tempest aren't the greatest on wet pavement anyway.

My opinion: on a high performace mill esp. with headers some kind of cold air induction is great, on a stock motor with basic manifolds, it may not be necessary, but it certainly won't hurt. Cool air to the carb is always a plus.
If rain is a concern (I used to live in WA) I think a homemade ram-air box on top of the carb with dryer hose run from the inner "headlight holes" is an excellent idea.

[Joe J-Truck]

I did have to rejet the holley to richen the mixture after adding the ram-air scoop. This fine with me, and makes sense due to more air flowing into the engine, it needs more fuel as well. I'm still in the process of tuning and dialing it in, but I'm quite pleased with the results so far.
:D

[Jerk]

I was wondering about the mixture thing, definately want to richen it for higher speed running, more airflow at higher speeds..duh ;) I got the idea for the cold air intake box from some article in hotrod or carcraft, someguy used a twin intake airbox and 2 3"flex hoses to the back of the inner headlight holes on a 60 something implala that was sortof set up as a "sleeper" street racer, so no visible hood scoop would give him a phsychological advantage over the poor goon that wanted to race him...i guess, I just thought it was a cool/unobtrusive way to get colder outside air to the carb. like I said I didn't see much improvement with it and I kind of needed the auxilliary lights so I put them in the intake holes instead. I'm all about clean lines and no ugly/useless-under-most-conditions gear being stuck on my jeep. :D I may still louver my hood some day to lose header heat in the summer and If I ever build a high speed race j20, I was thinking of air relief vent holes in the fenders just aft of the wheel flares, kinda like the cobras and some of the firebirds had, I don't know if they were funtional on both those cars, but it would help letting trapped air out of the wheel wells. plus they look cool ! :D

[ March 23, 2002: Message edited by: Matt W ]</p>

[chemijeeper]

Holy thread revival batman!

I was wandering through searches and I found this thread. It seems like it has a good amount of info, so I figured I would throw it back into the mix and see what everyone has to add. Anyone running cowl? ram air? pros? cons?

:drivin:

[jaber]

I would also like to see some feed back on this thread. Here in Az., any help with lower temps helps. This would also be a prime thread for the tech section.

[Tad]

Just stuff I have seen over the years from a quick search.

http://mysite.verizon.net/res6sw0u/jeep/exterior/vents1.jpg

http://mysite.verizon.net/res6sw0u/jeep/newhood/painted1.jpg

http://drbob.tqhosting.com/wagoneer/engine09.jpg

http://i6.photobucket.com/albums/y237/rstep/1639.jpg

Of course mine which as usual are too big and warped the hood.

http://i149.photobucket.com/albums/s80/tadsal/Wagoneer/hoodvent.jpg

[billyrb]

Man, how weird....seeing one of Ridgbak's posts......

[Lindel]

even wierder is seeing one of irbob's posts!

[Tad]

Man, how weird....seeing one of Ridgbak's posts...... Not half as weird as it is for me helping scrap that rig.
First roof rack on the original Ouray trip.
Creeps me out everytime we remove something from it.

http://i149.photobucket.com/albums/s80/tadsal/Wagoneer/Chris/towjob.jpg

Most of it's going to a good home.
The rest winds up as my problem :eek:

[yankeedog]

the only real downside i can see to rear facing scoops is that they would tend to clear out the engine compartment and put those fumes into your heat / defrost intake.i opened up the hole in the front valence panel behind the grille to make it bigger and flow more air that way.

[Jason D.]

For another suggestion, I know that the xj people seem to like the lebaron louvers for theirs. It looked pretty good from what I remember.

[chemijeeper]

http://www.eriejeeppeople.com/ejpforums/index.php?showtopic=5097

Theres a write-up for the lebaron louvers.

[Tad]

http://eriejeeppeople.com/Jeep_tech/XJ/hoodvents/16.jpg

I like that alot, thanks.

[Dmntxn77]

I used all 4 vents vents from behind the doors from a 1977 Celica a ZJ that I recently had.

I put the larger ones in the middle just like the Lebaron louvers, and put the smaller ones on the front corners. I caught some crap from the ZJ crowd for it, but I thought that it looked good (different is good). Of course, they think that the ONLY vents anyone should use are the Lebaron ones, or the factory 5.9 ones.

The real reason I did it though was to drop the under hood temps. Before the mod, I found myself getting REAL hot while in low range. After the mod, I never had a problem.

When I am not on my work computer, I will post a pic.

[Ralph Rogers]

My hood vents from a Fiero.

[chemijeeper]

Tad,
Anymore info on this setup. I think that looks real clean

[shadowjeep]

instead of actual vents and cowls, i have been thinking of drillling holes in the side of the hood just above the fender. fifteen or twenty of them should do.

[Tad]

Tad,
Anymore info on this setup. I think that looks real clean That belongs to one of the mod's here, rstep.
He does excellent body work.
http://www.fsjnetwork.com/fsjn/viewtopic.php?t=1858