Hood vents vs snorkel for a supercharged 80 (1 Viewer)

Joined
Aug 14, 2019
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In my experience the hood risers work well at trail and city speeds <30mph. Pulling fresh air from a snorkel will always help at any speed.

In my opinion the risers and louvers will not net the same results. The issue I see with your theory and antecdote is that the rear of the hood becomes a high pressure area at highway speeds; whereas the middle of the hood where louvers are placed is not.

You are correct and I didn't think about that. The area at the base of the windshield is a high pressure area - the old hot rods had their air scoops open to the rear to take advantage of that.

The risers are only $27 and ship free, so no pain to try them out.
 
Joined
Mar 6, 2014
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I Installed hood vents on my N/A 80 2 years ago and did a ton of testing. They are a bit more complicated than you might think, it kind of surprised me. First of all, I never had any overheating issues. One time about 8 years ago the AC shut off on a day where it was 122 out and there was a 2mph detour around a brush fire. I was pulling a travel trailer and was pretty heavily loaded on top of that, but it didn't boil over. 40k miles later, still no issues. All of this started after I bought a obd2 bluetooth module and the torque app. I got a bit obsessed with IAT's and coolant temps. Just before that I did 7 (yes 7) full cooling system flushes with vinegar, new toyota water pump, tstat, black hub with 10k silicone and tyc radiator with green prestone. Base Timing is about 7*. I was living in PHX at the time.

Before the hood vents I would see IAT's of 160-180 on the highway in 110+weather and coolant temps of 197-205. Even when I would get up to 7500ft elevation and the temps were in the high 70's/low 80's out, the IAT's would not come down. Coolant temps were pretty proportional to the outside air temp and would maybe hit 210 on a 6% grade on the hottest day.

I also noticed fuel boiling at high altitudes and heat, which seems to pretty much go away with ethanol free fuel.

After the hood vents, my IAT's were 5-10 above ambient on the highway unless I drove the truck then parked it for a while. The truck cools down way faster when not running with the hood vents, but it still heat soaks. After about 10 mins of highway driving my IAT's would be back down to normal. On the trail, things heat up slightly less than they did before and you can see heat pouring out of the vents, especially when the fan kicks on.

After about 20 MPH the hood vents start sucking in air instead of pushing it out due to how close they are to the cowl. I verified this with a yarn test. The vents blow right on the intake plenum and exhaust manifold, so thats why the IAT's drop. I had no real change in coolant temps, as they weren't bad before. In order to get hood vents to vent air out at speeds, they need to be almost directly above the radiator and they need to be louvered. Roughly 16" back from the radiator, a positive pressure zone exists at speeds about 20-25mph. That is why you feel air pushing through the vents when you are on the highway with the HVAC on outside air. This worked perfectly for what I wanted, and you don't get any smells in the cab when the HVAC is on outside air. I wanted the heat all going out under the truck on the highway and a place for heat to escape on the trail.

Overall, yes I would do it again, even though I now live in a cold climate.

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You can see a bit of the intake through the vent


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Joined
Mar 6, 2014
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Also, after adding vents the the center console area doesn’t get nearly as hot. Before it got hot enough that you didn’t want to rest your leg against it.
 
Joined
May 25, 2012
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Durango, CO
The highest heat is at the back of the firewall making fender vents my choice....if I had heat issues.
Interesting. I ordered the hood risers to try but this may be a good solution. Do you have any recommendation on vents/source? Trying to get the heat out from the turbo and allow better air flow for cooling and A/C to work better at low speeds...
 

60wag

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Jun 25, 2003
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Boulder, CO
Its good to see this discussion including the actual airflow through the hood vents and hood spacers. I always thought of the base of the windshield as a high pressure zone, ( that's where the HVAC intake is). But that is really only at highway speeds. Raising the rear edge of the hood should let some heat out when crawling at low speed but should suck in ambient air on the highway. Maybe that improves the heat flow out the bottom of the engine space at speed? Under the vehicle is low pressure at speed right?
 

thatcabledude

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Oct 20, 2011
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Walton Co, FL
I've got an LS swapped rig and have been steadily working out some of the kinks, coolant temp being one of them. Low speed and idling is great. These engines tend to be happy at 195 - 205. I've got dual electric fans and a powered AT cooler all moving air through the radiator. However, at sustained highway speed I see temps creep up to 215, sometimes higher. Never has spewed. My theory is I'm building up high pressure under the hood decreasing airflow over the radiator. Years ago I had a modified Datsun S30 Z car and they suffered from the same thing. It wasn't uncommon to see some creative ducting and venting going on.

Have been talking to my builder about raising the rear of the hood to test my theory - figure that's a much better way than cutting holes in the hood. The hood risers are a perfect solution. Just ordered a set and hope to have some positive results to report soon.
Does your truck have the rubber skirting between the frame rails and the inner fenders?

I ask because my truck NEVER gains temp while moving. Everything is stock on my truck besides those. They are gone.
 
Joined
May 29, 2011
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Location
Houston TX
I did RR sport vents and a subie STi Scoop - dropped temps by about 20-22 degrees at a median of temp of 95-98 ish - day before and pickup were roughly the same....verified on scanguage. I also have a dorkel that was done prior..... it certainly helps a bit as well.

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Joined
Sep 22, 2011
Messages
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I've got an LS swapped rig and have been steadily working out some of the kinks, coolant temp being one of them. Low speed and idling is great. These engines tend to be happy at 195 - 205. I've got dual electric fans and a powered AT cooler all moving air through the radiator. However, at sustained highway speed I see temps creep up to 215, sometimes higher. Never has spewed. My theory is I'm building up high pressure under the hood decreasing airflow over the radiator. Years ago I had a modified Datsun S30 Z car and they suffered from the same thing. It wasn't uncommon to see some creative ducting and venting going on.

Have been talking to my builder about raising the rear of the hood to test my theory - figure that's a much better way than cutting holes in the hood. The hood risers are a perfect solution. Just ordered a set and hope to have some positive results to report soon.
I have an LS swapped 6.0 80 as well in Phoenix AZ.
The electric fans are the common issue here they can’t keep up as well. Swapped to the OEM GM fan clutch and even with 115 degrees today never gets over 205 .
 

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