Controlling Under Hood Temperature?

horseballz · Jun 2, 2013

Hi Folks,
I guess I'll start off the season of temp related discussions!View attachment 128402 So my 68 Coupe is a victim of blazing hot under hood temps, especially when, or just after, using the air conditioning. As is becoming more & more common with the deterioration of quality in gasoline, this excessive heat creates a whole slew of issues. In my case, I get carburetor boil out, (leaving a flooded engine condition after parked for 10-30 minutes followed/compouded by a dry float bowl and or vapor lock, unless hood is left open), idle degradation while at a long traffic light, etc, etc! Bear in mind, these only really become a problem when ambient temps climb to 105 degrees and above (Sometimes near 120 & more at the level of 2 feet above the pavementView attachment 128403) Anyone have any good ideas to combat these issues? Ive been considering:
A-Finding a crap hood (Mine is a turn signal model) to butcher for louvers or a scoop to ventilate the engine compartment.
B-Adjusting hood hinges to allow the rear of the hood to live 1/2" to 1" above the level of the cowl. This looks like CRAP!
C-Electric fan, set to stay on for a while after engine is turned off. I realize this won't do a lot to lower the overall engine temp, but might be just enough to help evacuate an adequate amount of under hood heat. The real downside of this is the added toll it will take on the battery. Unless using a pricey "deep cycle" battery, the battery life is seriously compromised by repeated discharge & charge cycles.
I already have ceramic coated headers, a phenolic carb spacer, well placed clutch fan with a proper shroud and a good aluminum radiator.
Any Thoughts?
Gene

other_shoe · Jun 2, 2013

I think the after-run fan on my 86 Audi did a fair amount of good, but these are very different cars.

I kind of think you should do some experiments comparing active and passive ventilation. You put a temp probe under the hood and then use a box fan in front of the grill to imitate the fan solution, mapping out what happens to the temp in the next 15 to 20 minutes, and then at a very similar start temp and outside air temp maybe temporarily adjust the hinges to passively vent and map again.

My gut tells me that the hood scoop and louvers is probably best since I've had all sorts of trouble with electric fan failure and I think it might look neat, but that's not really reasoning.

horse sence · Jun 2, 2013

what radiator are you running? i had trouble with some of the new brass radiators as the tubes were to small to move enough water through them.
some even had pluged tubes from solder when they assembled.

horseballz · Jun 2, 2013

24" x 16", 3 x 1/2" tube core aluminum "Champion" radiator. I have very little issue with engine/cooling system temps, but the under hood temps are through the roof. These temps seem to be exaggerated by the efficient heat transfer of the radiator. All this appears worst when sitting in traffic or parked for a short time. I've been toying with the idea that instead of a big electric radiator fan, a couple of low power draw units down by the toe boards, pointing downwards to evacuate the engine compartment. Set them up to come on ONLY after car has been shut down and have them run for 10-12 minutes. I've never seen it done, but it seems as though it might be effective. I agree that louvers are probably going to end up being the most practical/effective solution. Running with the rear of the hood "up" will likely give similar results as the louvers and will be a zero cost, low labor test scenario. Thanks for the thoughts and please keep them coming.
Thanx,
Gene

Rusty67 · Jun 2, 2013

Even though your headers are ceramic coated you could likely drop the temp under the hood by heat wraping them.

If you run an electric fan as your main fan it might run the battery down as you said but you might be able to run some smaller fans that don't have as much of a draw to push some fresh air in there and keep the temps down while parked without killing a standard battery. Of course, you should run a 3G or 6G alternator instead of the old style one because you will need to charge the battery faster no matter the size of the fan(s) you run.

horse sence · Jun 2, 2013

i bought a set of louvers from stang-aholics for a buddies car. they are carbon fiber and look decent when installed. i put them on a fiberglass hood but they will fit just about anything.

candphall · Jun 3, 2013

Hey Horse Sense is there anything you can't do?

Fstbk · Jun 3, 2013

I am diggin those vents man!

horse sence · Jun 3, 2013

candphall said:
Hey Horse Sense is there anything you can't do?

yeah, keep my computer from crashing.it crashed again last night. after fighting with it all day finaly got it up again.....i hope!

horse sence · Jun 3, 2013

Fstbk said:
I am diggin those vents man!

yeah ,these are carbon fiber and look very nice .i think they would look good painted or left as they are. i have put them on 3 hoods ,a short 67 with shelby hood scoop, a long 67 shelby hood
and a 66 with shelby scoop. they look great on all of them.

horseballz · Jun 12, 2013

Yeah,
I'm thinkin' of goin' with a pair of these:

http://rodlouvers.com/Pair-of-Angled-11-Louvered-panels-P1036801.aspx

as those carbon fiber units gotta be WAY pricier than $28. FWIW, I raised the rear of the hood/hinges to give a 3/4"-ish gap between the hood and the cowl. With the gap for ventilation, it has cured the hot start issues.
Thanx,
Gene

65ShelbyClone · Jun 18, 2013

FYI, the cowl and base of the windscreen is a high pressure area when the car is moving. It doesn't help underhood ventilation unless the car is stopped. The middle of the hood, on the other hand, is a low pressure area when moving and with that in mind, I see louvers being far more effective than lifting the rear of the hood.

That's why the Mustang SVO intercoolers didn't really work; they were right above the cherry-red turbo and manifold and the scoop was in the hood's low-pressure zone. At road speed they would pull hot air backward through the intercooler.

Controlling Under Hood Temperature?

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