I noticed the hood on my 81 seals completely around the engine compartment. It does look like an area could be opened up to allow for cool air or even some of the hot air to escape. Has anyone ever tried to drill holes or open up the area under the hood to allow for some cowl venting? Alot of air enters the engine compartment, but not alot of area for air to leave. thanks Allan

 

Hot air vent in the area described would be sucked into the passenger compartment via the windshield plenum.

That's why there's a seal around the engine compartment.

 

How, would this produce more heat into the cockpit? The area I was talking about opening up was on the hood. My hood has an area about 2 1/2" by 16" which is a flat spot just above the aft seal area. Please elaborate for me. thanks Al

 

That is a realistic concern.
The modern Vipers have hood vents, some bb Chevelle guys have put hood vents in to solve bb cooling problems.
Most vents are nearer the middle of the hood.
Make sure you have the chin spoiler and the area from the bottom of the core support to the front xmember blocked off just like the original shrouds did if you have electric fans.

Almost all cars have the fresh air intake at the base of the windshield area. Turn your a/c blower on high and put your ear near the passenger side hood latch/pin, you'll find it.

 

I guess I'm not following you where you want to make this opening. If it's on top of the hood and forward of the seal, AND if hot air were to flow outwards, it would likely flow into the plenum at the base of the windshield.

 

Ok, now I understand how hot air may be directed into the cabin area. I don't have a cooling problem at all. I just thought is was odd to not have more air flow out of the engine compartment. Al

 

I have a 73 and there is a vent that is held on by 4 bolts? anyway remove the vent housing and I cut out the inside layer of the hood, you should be abel to look thou the windsheild and see the air cleaner, what this does is at drivign speeds the airflow over the hood and up the windsheild will create a neg presure and suck air out of the engine copartment this will get more air thou the Rad. I did this and put a scoop insted of the air dam under the front so I am pumping more air in the front and sucking it out to, I
dropped my temps 40-50 deg. I have no problem with hot air in the cabin.

 

But...you live in Wyoming?? How hot does it get there? As mentioned above, if hot air is allowed to 'escape' at the rear of the hood, the air will just get forced into the passenger compartment air intake plenum due to pressure build-up at the base of the windshield...unless you have it sealed off (not a particularly good idea).

 

Yes we get some hot days here in the summer, just wanted to make the piont, I have done it like that and I do not have any problem with heat in the passage compartment, like they say don't knock it before you try it.

 

GM went to a lot of effort to seal the engine compartment on 81s. The emission controls required higher operating temps to more efficiently reduce emissions. This is why cars in the 70s switched to 210 and higher thermostats.

The only air that entered the engine compartment came up from under the bumper and through the radiator. The radiator core support has seals all around it so that no air enters the engine compartment, except through the radiator. The seal you have at the rear edge of the hood is actually a weatherstrip designed to keep water out of the engine compartment, not to seal air in. Every Corvette hood from 53 to 1982 had a hood ledge weatherstrip. On 81, you have 2 air boxes, one on top of the radiator and one to the right of the core support, that direct cool air to the air cleaner, this is the only area where air should enter the engine compartment without going through the radiator.

Chevrolet actually did make provision for drawing hot air out from under the hood. The black plastic louvers in the fenders, behind the wheel wells, are designed to do just that; draw hot air out from under the hood.

I do agree with others here that adding vents to your hood could increase your cockpit temps. Interior fresh air is drawn into the interior at the base of the windshield. Venting 200+ degree air through the hood would cause it to be drawn into the vent system. You can test this yourself. Get your car up to operating temperature and while driving down the road with the outside air vent and fan on, pop the hood release; this should allow enough underhood air to escape to creat the same effect.

If I correctly understand where you were concidering openning the hood "an area about 2 1/2" by 16" which is a flat spot just above the aft seal area", I doubt that it would do anything to remove air from under your hood anyway. Any portion of the hood, beyond the rear weatherstrip, is not in your engine compartment. The rear hood weatherstrip seals the engine compartment at the rear drip edge on the firewall/cowl. The portion of the hood beyond the weatherstrip is actually over the windshield wiper compartment, which is sealed off from the engine compartment.