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Cuttin' up my hood?


Gone but not forgotten
Jan 30, 2001
Hermosa Beach, CA
1987 Z51 Silver Coupe
Has anyone ever simply taken a stock clamshell and cut out a portion of the bracing the area at the rear the hood? It seems to me that it serve as a fine way to reduce the underhood temperature by releasing the hot air. (The actual high pressure area is about four to six inches ahead of the windshield bottom, right?)


You wouldn't have to cut the whole thing away, just the portion in the middle. Only the two sides of the brace is all that needs to be cut. It would probably help to seal it with a sleeve or something else easily fabbed. Whaddya think?

We're on a wavelength...

I've thought the same thing....

About venting the top of the hood for air to circulate around the engine better.

The biggest drawbacks that I've thought of...
1 You'd have a hole in your hood that isn't for something cool like a blower.
2 It may improve air flow, but may not make any engine temp difference.
3 In the rain (or in the event of severe oil/radiator leakage) you may be blinded by steam or smoke coming through your new hole in front of the windshield! (but you'd be alerted to major problems right away)

Just some thoughts I've had.
Open Hood

I recently bought a 62 hood with an L88 scoop in it. You can see it in the picture below on the left. It has made a nice cooling difference allowing the air to exit as well as it enters. The scoop was done in such a manner that neither brace was altered at all, middle of the hood or rear. That would be my concern if I were you, making the hood weaker in any way. It has changed the whole look of the 62 and I LIKE IT!!! :)
I was looking under the hood trying to figure out how to get some of that trapped hot air out of there and had a different idea that wouldn't require cutting anything that anyone can see.
Looking around the upper A arm it is open to airflow even with the hood closed.
So what if you got 1 or 2 small muffin fans and hung them in there in the opening. That would pull hot air out of the engine compartment. If you could get them aligned right you may even get them to blow the air towards your rotors to use it to help cool them down. Kill 2 birds with 1 stone ;)
Possibly cutting a small hole in the inner fender at the back would pull air from the dead space inbetween you exhaust manifold and the sidewall. That may be a possibility.
I looked where the gills on the side of the quarter are and they are pretty much just for show. It doesn't look like you could get a fan in there to draw air out or in very well. Which is a shame. Then they might actually be functional.
Not sure how big a muffin fan and how much cfm it would have to move to be useful. Just thought...
Graham, they do sell those fans in a kit. ;)

Heidi and Lou, I don't mean to cut a hole in it, I just mean to cut out both sides of the support brace at the rear of the hood, to either release hot air, or allow fresh air to enter from the high-pressure area at the base of the windshield. The seal at the rear of the hood, between the hood and the firewall, would still function as designed, and there would be no noticeable difference externally.

I have already removed the foam rubber (?) seals at the rear hood sides, and believe it or not, it seems to have made a slight difference. From what I gleaned from Gordon Killebrew's book, they stopped sealing that area in the early nineties.

Ken, interesting question. Sounds like the idea would easily work if the car never saw water. If it got rained on or simply washed with a hose, water could easily get in the engine bay....probably right down the firewall where most of the electrical wires come out. What I eventually want to do is go with heat extracting vents. I know Geenwood makes a really sharp looking pair for C-4's. A good friend of mine has them on his ZR-1. The only problem is they're around $500.....but they look awesome :D

The only thing about the extracting vents is, Jay, I don't want anything to show. ;)

As for water getting into the engine compartment, take a look at yours and notice that the area of which I speak is separate from where the hood seals to the fiewall. The seal would still function as designed. Note that I'm talking about cutting on the verticle plane, not the horizontal plane. ;)

When I first bought my '90, I realized this would be a problem. Being a part owner of a sound and light company, I put a fog machine in the engine bay to see how the whole thing would vent. Well....C4's don't!

I tried the fan tricks, great, they run all the time but, the problem is improper venting. Took out the rubber moulding like suggested, and it didn't make a big difference. I tried taking the center panel from the wheel well, and all it did was suck brake dust all over the motor. :(

That's not a bad idea Ken. Problems with that is moisture getting to the distibutor, and seeing how C4's flex, and the hood being the biggest piece, are you sure you would want to cut a brace? Wouldn't that promote cracks and stars too?

Jay, is this what you are talking about?


As soon as I can I am installing them and with my redesigned hood, I am hoping it makes a big difference on venting/cooling.

I need more free time!
Barbie said:
...Jay, is this what you are talking about?


Barbie, those are the ones. I know Greenwood makes them, but I've been having a hard time locating a set. Where did you get yours?


Ecklers makes exactly what your talking about. A fan kit that attaches to the A arm assembly. It consists of 2 fans and an inner fairing kit that replaces the inner fairing of the wheel well.

Check it out on www.ecklers.com

If you guys go to "www.corvettecentral.com"

there is a louver set in there for the hood.....much the same as the Green wood pair..only 5 small louvers instead of 2 big ones.

And they are only 146.00 for the pair.

they have a pcture of them right on the site......im buying them when i get my vette......and im also buying a high rise hood with 2 air ducts on it.......

the price of the scoop is 325 i beleive....i know its 3 somethin!!

To get to the louvers (for C-4 and C-5 models) just click "search" ....and type in "louvers"......annnd BOOM..there they are.

they look much like the louvers found on the hood of the Viper GTS.
vms4evr said:
I was looking under the hood trying to figure out how to get some of that trapped hot air out of there and had a different idea that wouldn't require cutting anything that anyone can see.
Looking around the upper A arm it is open to airflow even with the hood closed.
So what if you got 1 or 2 small muffin fans and hung them in there in the opening. Not sure how big a muffin fan and how much cfm it would have to move to be useful. Just thought...

Funny U should mention this since they actually do sell kits (where I cant remember--but it was major one) that do the same exact thing mounted just there!...they claimed they worked so U could probably do it much cheaper anyway!

My initial question here was:
"Will it affect the structure if I open a hole on either side of the brace (and seal it somehow so that air doesn't get trapped in the space between the bracing walls), right there in the middle of the hood, in the raised portion of the hood? The rubber seal around the firewall, at the rear of the hood, will still be able to seal as it was designed."

:L Ok, maybe that wasn't an exact quote but do you get the idea now? I don't want to use the "fans in the A-arm" because I don't want to screw around with the wiring anymore, and I don't want to use the "Daytona" type extractors because I don't want to mess with the exterior visualizations of the hood itself.

My thinking is that air entering the front of the engine compartment would find an additional place to exit, via the opening created by cutting through that brace. I have already removed the factory seals at the rear of the hood sides, and believe it or not, it seems to have helped cool the engine compartment down somewhat. Of course, when I bypassed the coolant flow around the throttle body helped to make a difference as well.

The engine itself is not running any cooler (I never really experienced anything that could be considered out-of-the-ordinary for today's engines.), but the underhood temperatures seem to be. ;)

BroKen :w
Always trying to be cool!


When I had my V8 Fiero I ran into some problems keeping it in a safe cool zone. It never boiled over, but would get pretty warm on the highway, and actually cool off in traffic.

One day while cruising down the highway, I pulled the hood latch (No worries, they open backwards like Vettes). This let the high pressure air escape from behind the radiator faster. I ended up with a 40 plus degree drop.

So, I won't go into the details of how I then modified the car to stay cool as that is way off topic. What I can say, is it made a huge difference on that car. Bottom line is, the radiator is only as efficient as the air that can travel through it.

One other trick to try. If there is anyway to extend the factory air dam that is in the center of the nose closer to the ground. Here is the scoop (pun intended). The lower that is to the ground below the radiator, the higher the pressure that it forces into the front of the radiator, and the lower the pressure behind to help direct the air up over and down. After making the front chamber mods on the Fiero I saw the 40 degree drop. Then, I lengthened the front lower scoop, and dropped almost 40 more. I ended up taking the lower scoop and trimming it to half that size. That kept me at 180-190 in the heat of summer with the air on high.

With all that said Ken, Nikki's 90 won't get hot now. We put a pair of new cooling fan motors, new stock replacement radiator, 180 Robertshaw High Perf. Thermostat, and cleaned out all the crud up front. Finally, I rewired her fan so one comes on and stays on with the engine, and the other only comes on with the a/c. I can't get it over 190 (except at AutoX where it hit 195 or so after 75 seconds of WOT and brakes).

I plan on rewiring her primary fan on a simple thermostat sender that will kick the fan on at 180, and off at 160. This will help while cruising down the highway as it will most likely shut off and let the cruising air do the trick. In fact, the electric fan is a henerence at speed, as the natural force of the air is greater than what the fan can pull.
Thanks for the tips Chris, and if I run into overheating problems I'll be sure to keep those tips in mind. :upthumbs

What I'm trying to get at here is the fact that the underhood temperatures get so high, and because of this I have problems (like I had on the road trip) with the wiring becoming dry and brittle. As a matter of fact when I was fooling around with it the other day, the EGR connection came loose and the piece of insulating/aligning plastic around the center pin broke and fell out. When I tried to pick it up, it crumbled in my fingers. :eek

Part of this is age obviously, but a lot of it could be alleviated by allowing some of the underhood temperature to escape, which, I thought, by doing this modification, should perform the same basic function as what you described in the case of your Fiero. And just because the hood opens backwards, doesn't mean I want to go driving around like that -- I did that in the sixties! :L We'd prop up the rear of the hood with spacers or washers on the rear bolts of the hinges so the hood would stay open back there for about an inch-and-a-half or two. :eyerole

At any rate, my question still remains -- "Will it hurt the structure of the hood?" I wouldn't think much if at all, but I'm seeking opinions, so keep 'em coming! :upthumbs

Man Ken, I thought I got up early for a East Coast boy. It is 8:15 now and I am heading out to the shop to do a little more body work.

When C4s were newer, it was not unusual to find complete hoods at body shops everywhere with minor damage requiring a complete replacement. Most of them would give you the hood to get it out of their way. I know, because I took several of them home with me years ago when I worked at a Chevy dealer. Now they are getting a little harder to find for free. In any event, if I was you I would look for one. Fix the collision damage, then cut it any way you want.

Now, You can pop it on the car and experiment with minimal investment. Too bad we are not closer, I know where there is a hood off of an 85 with a small crack in the right rear corner near the door that is free for the time it takes to drag it home.

I had that thought in CA when 78 had runhot problems.

Originally posted by 69MyWay:
"...extend the factory air dam that is in the center of the nose closer to the ground."

All of the mechanics and body shop people I spoke with gave me that "funny" look. I don't know what the look meant...(I don't know what you're talking about)...(silly girl, that won't work)...However, it could very well have been...(you want to do WHAT to your Vette's appearance?) Anyhow, being met with so much opposition and resistance, I abandoned the idea. After reading your post, I see that I was not very far off the mark with my thinking, but 78s runhot problems have been minimal since our move, so I no longer need to consider such drastic measures.

I can't really take credit for that idea. There was an awesome article in Car Craft about a 69 Camaro with a massive big block and air that had terrible heat problems in..........California.

They went into a detailed explanation with vortex diagrams showing the air pressure in front of and behind the radiator. The cool thing about this is that we are talking about the little plastic one that is nearly just below the radiator support. It can't really be seen unless you look down low. A lot of hot running vettes have long lost or damaged theirs. Anyway, in wind tunnel research, much has been learned about that. They have found that the stance of the car (height in front vs. rear) that can vary from car to car due to wear and tear, engine options, tires size, etc. will also affect the efficiency of the air dam function.

Just food for thought. They actually suggest using a factory part number air scoop from a late 80's firebird as it is the largest available. It can also be cut to fit nearly any car. At about $40 new, and maybe $5 at the bone yard, it might be worth looking into. Oh ya, the way the car sits (tire size, springs, etc) is often why two otherwise identical cars may have different operating temperatures when out running on the road. The one with the lowest front air dam gets the coolest temps.
Thread revival time, not that it really matters. :eyerole

I was just looking at this thread again and although I haven't thought about open that up in a while, it just dawned on me the now that I will be utilizing the Miniram, I will have a lot of extra room above my plenum.

That reminded me of something I saw somewhere once where the guy had the hood with cowl induction, only he ran a couple of runners(?) from the rear of the hood (the cowl induction part) to the front of the engine so he had cool air entering the throttle body. It may have been a raised hood to begin with, but the runners don't have to be huge.

Just another thought on it. :eek:

_ken :w

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