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Hood venting

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Old 06-26-2019, 06:59 AM
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The Punisher
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Default Hood venting


So I found this pic on facebook. The owner had recently bought this car and wasn't sure if the hood is stock height with front venting cutout. Does it look stock height. I kinda like the vent cutouts in the front. The car is a '75 greenwood sports wagon conversion.
Old 06-26-2019, 07:02 AM
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The Punisher
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Another pic
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Old 06-26-2019, 07:05 AM
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bashcraft
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The hood looks too high to be stock, and the first thing I thought of when I saw the cutouts was the chicken on a trans am hood. Not a good thing.
Old 06-26-2019, 08:20 AM
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7t9l82
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That's the stock hood. I have a friend that did the back end close to the windshield, but his didn't have the factory vents to start with.and he did it far enough forward of the windshield that it vented before the firewall.
Old 06-26-2019, 08:29 AM
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fishslayer143
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haven't seen a Greenwood Sportwagon in years.. they were popular in the 70s early 80s .. built a couple in my shop.
Old 06-26-2019, 09:22 AM
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Bikespace
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That looks like the stock hood. I don't think those vents do anything useful, though. You'd want them a bit further back to extract hot air from past the radiator, like on a C7.

What does the underside of the hood look like?
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Old 06-26-2019, 12:13 PM
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Originally Posted by Bikespace
That looks like the stock hood. I don't think those vents do anything useful, though. You'd want them a bit further back to extract hot air from past the radiator, like on a C7.

What does the underside of the hood look like?

Do you think it would help flow air out the back vent?
Old 06-26-2019, 01:07 PM
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CA_WxMan
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Originally Posted by The Punisher
Do you think it would help flow air out the back vent?
The grill at the rear of the hood is actually an inlet to an airbox above the air cleaner. Essentially a cowl induction setup.
It draws air from the high pressure area at the base of the windshield and routes it into the air cleaner.

You can't vent air out the back of the hood because of the high pressure there. Also, you don't want vents ahead of the radiator, because it decreases the radiator efficiency.
If you want to vent the engine compartment through the hood, you need to do it in the area behind the radiator back to about where the rear of the carb/air cleaner is.
Another option might be to increase airflow out the side vents.
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Old 06-26-2019, 01:16 PM
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Greg
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I like it.
These conversions were cool back in the 70's. Then they were gay for a while. Now they're old enough to be nostalgic again. I'd buy one if the price was right.
I agree with the others here, I think the vents up front would defeat the purpose of the radiator seals for good cooling effect.
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Old 06-26-2019, 01:39 PM
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Seems the cheezy hood vent let the air out of the tires. lol
Old 06-26-2019, 04:31 PM
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Bikespace
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Originally Posted by The Punisher
Do you think it would help flow air out the back vent?
Originally Posted by CA_WxMan
The grill at the rear of the hood is actually an inlet to an airbox above the air cleaner. Essentially a cowl induction setup.
It draws air from the high pressure area at the base of the windshield and routes it into the air cleaner.

You can't vent air out the back of the hood because of the high pressure there. Also, you don't want vents ahead of the radiator, because it decreases the radiator efficiency.
If you want to vent the engine compartment through the hood, you need to do it in the area behind the radiator back to about where the rear of the carb/air cleaner is.
Another option might be to increase airflow out the side vents.
That about covers it!

I'd add that later in production, there is no longer an inlet at the rear of the hood. On my black 79 (same hood, without the cutouts), there is a rubber seal at the rear. If it is absent, it will reduce cooling efficiency, as air will be forced in ahead of the windshield, and act to block air that would otherwise flow through the radiator.

Unless the vents at the front of the hood (or the rear of the hood) lead ONLY to the air cleaner, you will at best do nothing beneficial, and at worst defeat your radiator's cooling efficiency. I should caveat that by saying there are several on this Forum that do exactly that, reduce the available inlet air to the radiator, because they race their cars, and minimizing flow under the car at speed is important for handling, and at speed they get enough flow over the radiator to cool the car.

But if it looks cool, don't worry about it too much. The C7 extractor (behind the radiator), both looks cool AND is functional.
Old 06-26-2019, 08:03 PM
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I like it, old school look.
Appears to be a stock hood tho.
Old 06-26-2019, 11:48 PM
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I like it. And that rear window looks pretty cool. What the heck anyway? It's a 75 so you can't really hurt the value.
Old 06-27-2019, 08:50 AM
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You can't vent air out the back of the hood because of the high pressure there
Thanks for the info CA_WxMan, I had cut holes to vent on the back, underside of the hood thinking it would help airflow. I noticed a bump up in temperature but had attributed to something else. I will be sealing it up.

Always learning something new in this forum!
Old 06-27-2019, 09:08 AM
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Kacyc3
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Originally Posted by carriljc
I like it. And that rear window looks pretty cool. What the heck anyway? It's a 75 so you can't really hurt the value.
Could you imagine the cost of paying someone to do the conversion today?
Old 06-28-2019, 08:59 AM
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This is what I plan to do to my new hood. C7 hood vent.


Last edited by Bee Jay; 06-28-2019 at 08:59 AM.
Old 06-28-2019, 09:07 AM
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DblTrbl
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I'd like to see how that looks on one of our stock hoods. I got a Turbo to cool under there.

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Old 06-29-2019, 02:34 PM
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mardyn
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I like the way the 4 vents look in the photo above, but seems to be too close to the radiator to be effective...

There is an aftermarket vent kit similar to the C7 style that's designed for a C3 hood... it looks pretty decent
but I can't remember the name off hand.

mardyn
Old 06-29-2019, 04:28 PM
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venting when you are sitting still imo more important, I say let that hot air rise and get it out any way you can.

Seen a few use ZL1 pieces which function..its more work but then they are molded in they look so much better than being riveted, glued on etc.

Like those wagons, pretty unique. He wont see another one on the road like his thats for sure.
Old 06-30-2019, 10:54 AM
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Richard454
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Originally Posted by DblTrbl
I'd like to see how that looks on one of our stock hoods. I got a Turbo to cool under there.

Here's a few-





Fellow forum member "Denpo" hand made these-




Here's what I thought would be a "cool" idea- especially with a low profile LS engine- L88 hood with a fan- artist rendition



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