Can a hood scoop cause overheating?

Posted By: VITC_GTX

Can a hood scoop cause overheating? - 07/09/11 06:26 AM

'71 Demon with 5.9 Magnum. Original '97 5.9 with new cam and 650 carb and 160 thermostat. Runs about 380 horse. Car has fiberglass sixpack hood.

Two row aluminum rad with two electric fans with shroud. Car runs ~190 in town but on the highway it will hit 230. I have a spring in the lower hose so it shouldn't be collapsing. I was wondering if the sixpack scoop could be doing this. The hood lifts about 1/2" in the back at highway speeds due to the air being forced into the scoop. Could this cause a positive pressure under the hood that would restrict air coming through the rad? Could it be the shroud restricting the air flow?

I wouldn't think this engine should have a overheating problem.

Posted By: ademon

Re: Can a hood scoop cause overheating? - 07/09/11 06:50 AM

mine does this with the sport hood, 180 in town then about 200 hwy. never did try to block the scoops, your scoop is much larger

Posted By: thedriver

Re: Can a hood scoop cause overheating? - 07/09/11 03:20 PM

Maybe. With the extra air you are running lean, thus running hot?

Posted By: feets

Re: Can a hood scoop cause overheating? - 07/09/11 03:25 PM

If it's not sealed to the air cleaner it can reduce the air drawn through the radiator a wee bit. It shouldn't make more pressure than the air moving through the grille.

Electric fans with shrouds? What kind of fans? Some of the cheapies (and not so cheapies) don't flow enough air to keep up with highway speeds.

Posted By: johnzgarage

Re: Can a hood scoop cause overheating? - 07/09/11 03:33 PM

The chances are you have a cheap themostat from your local parts store. Replace the themostat with a high flow one. ......Had the same problem.

Posted By: VITC_GTX

Re: Can a hood scoop cause overheating? - 07/09/11 05:32 PM

Quote:

If it's not sealed to the air cleaner it can reduce the air drawn through the radiator a wee bit. It shouldn't make more pressure than the air moving through the grille.

Electric fans with shrouds? What kind of fans? Some of the cheapies (and not so cheapies) don't flow enough air to keep up with highway speeds.

Unfortunately I don't know what kind of fans they are. I bought the system here from a Moparts member. I would think I wouldn't even need the fans at highway speeds. When I turn them off the temp doesn't change (on the highway).

Posted By: MoparforLife

Re: Can a hood scoop cause overheating? - 07/09/11 05:43 PM

Quote:

Quote:

If it's not sealed to the air cleaner it can reduce the air drawn through the radiator a wee bit. It shouldn't make more pressure than the air moving through the grille.

Electric fans with shrouds? What kind of fans? Some of the cheapies (and not so cheapies) don't flow enough air to keep up with highway speeds.

Unfortunately I don't know what kind of fans they are. I bought the system here from a Moparts member. I would think I wouldn't even need the fans at highway speeds. When I turn them off the temp doesn't change (on the highway).

You are right in most cases you would not need a fan a highway speed as the forced air is plenty but in this case the fans may be blocking the flow at highway speeds. Adequate air flow at hiway speed may also depend a lot on the RPM's turned at said speeds.

Posted By: Stroked_Hemi

Re: Can a hood scoop cause overheating? - 07/09/11 08:56 PM

I'm going to lean towards what feets is asking about, the fans and rad setup.

Typically when it comes to aero, if the hood scoop is not sealed, it will help cool the engine, because the air coming in will pass around the engine, exhaust manifolds / headers, etc.. and go under the car, yet this results in a handling disadvantage since this will promote front end lift at high speed.

Good luck,
Mike

Posted By: feets

Re: Can a hood scoop cause overheating? - 07/09/11 10:18 PM

Quote:

I'm going to lean towards what feets is asking about, the fans and rad setup.

Typically when it comes to aero, if the hood scoop is not sealed, it will help cool the engine, because the air coming in will pass around the engine, exhaust manifolds / headers, etc.. and go under the car, yet this results in a handling disadvantage since this will promote front end lift at high speed.

Yes and no.
Vehicles at speed create low pressure areas behind the radiator. The radiator is an obstruction to air flow. Therefore, it has higher pressure in front than behind.
Chin spoilers and under covers increase this low pressure effect and actually help draw more air through the radiator.
Hood scoops that do not seal to the air cleaner or carburetor force air into the engine compartment and greatly reduce the low pressure area behind the radiator. That kills the additional suction behind the radiator.
Sealing the radiator to the grille so air can't get around it slightly increases the air flow. The problem is the air will only stack up a wee bit before venting around the grille opening and over the hood.

Air is a funny thing. It flows like a liquid but can be easily compressed.

I'd like to see the fans and shroud on this car. If it's one of those flat faced square cornered "pretty" aluminum fan shrouds it needs to go in the trash.
It might be possible to "save" some of those by making some flappy cutouts in the flat parts of the shroud. They open towards the engine to allow air trapped by the shroud to escape. At low (or no) speed the fan draws them closed and pulls more air through the radiator.
Look at this factory style Viper fan and you can see how much air the engineers wanted to vent out of the shroud.

Posted By: Stroked_Hemi

Re: Can a hood scoop cause overheating? - 07/09/11 11:01 PM

This discussion can surely get complex, but for the old Demon having a hood scoop which isn't sealed, it will surely keep the engine cooler, even going back to the old Hemi Super Stock Barracudas and Darts, some would find that it was better to run without the plate that seals the carbs to the hood because the cooling benefit would outweigh the ram air effect for performance on the drag strip.

Edit.. removed my excessive babbling..

Cheers,
Mike

Posted By: 13ChargerR/T AWD

Re: Can a hood scoop cause overheating? - 07/10/11 01:34 AM

Ive got the OPPOSITE problem it will get into the 200's in town/traffic/stop and go with not a ton of air flow but cools right down to 175-180(180 thermo) on the road. ive got a 6 pack scoop a Eddie 750 and its a 340 engine with stock cam and im guessing 8.5 compression. its a stock radiator with a typical 340 fan(no clutch fan just a "regular" one) and its got the shroud in place. Also not a sealed unit(obviously by picture)

Attached picture 6721590-Dart_Sport_002.jpg

Attached picture 6721590-Dart_Sport_002.jpg

Posted By: GTXX

Re: Can a hood scoop cause overheating? - 07/10/11 02:39 AM

it could be. conflicting theories. duct tape the opening of the scoop and reach an unscientific conclusion....

Posted By: Stroked_Hemi

Re: Can a hood scoop cause overheating? - 07/10/11 04:38 AM

Quote:

it could be. conflicting theories. duct tape the opening of the scoop and reach an unscientific conclusion....

ding ding.. give that man an award! (sarcasm not implied), something to test.

Edit.. removed my excessive babbling..

Cheers,
Mike

Posted By: feets

Re: Can a hood scoop cause overheating? - 07/10/11 09:51 PM

Quote:

Ive got the OPPOSITE problem it will get into the 200's in town/traffic/stop and go with not a ton of air flow but cools right down to 175-180(180 thermo) on the road.

When that happens it's usually a sign of low air flow across the radiator at low speed.

Posted By: old340dog

Re: Can a hood scoop cause overheating? - 07/10/11 10:35 PM

I opened up my hood scoop when we did my motor rebuild in my duster 340. Since the hood was off I figured it would be a good time. I seem to run around 200 on the highway. But have had some issues with getting the carb mix right. This topic has praised some questions and issues I have wondered in regards to air/fuel mxture. One thing I have had on mine is a K and N extreme air cleaner lid and air cleaner. I changed it yesterday,and took the car out for a run. To me it seemed like the car ran a little better and was a little more responsive.Since I didn't have so much air coming into engine bay.

But what do I know.

Posted By: VITC_GTX

Re: Can a hood scoop cause overheating? - 07/11/11 02:19 AM

Feets-

Here is a pic of my shroud setup. Sounds like I have the type you don't care for too much. I wonder if no shroud is better than this shroud???

Posted By: VITC_GTX

Re: Can a hood scoop cause overheating? - 07/11/11 02:21 AM

Another pic.

Posted By: Mopar_Country

Re: Can a hood scoop cause overheating? - 07/11/11 03:12 AM

I would think that setup is blocking a lot of air flow through the rad. Step up to a 180* stat and put a standard shroud and fan on there.

Posted By: johnedod

Re: Can a hood scoop cause overheating? - 07/11/11 03:48 AM

I have an open 6 pack scooped hood on my 68 road runner. Mine didn't run hot with the stock hood and it doesn't run hot now either. My scoop isn't sealed to the breather. No radiator weatherstrip at the front of the hood or cowl weatherstrip at the rear.

for what it's worth.