Hood question

[Bio}{azard]

I have a Cowl-induction hood on my vega right now, and would like to know the principle behind the hood, does it let air in, or out? And if it lets air in, what kind of hood should I look for that lets it out?

[TheSilentChamber]

They're mainly just for clearance for taller carbs/filters, but some logic on the induction could come from the fact that a point of high pressure is usually at the base of the windshield.

[curtis73]

Yes, cowl induction works by letting air IN. There is an area of high pressure at the base of the windshield.

There is probably not anywhere on your hood that you could use to let air OUT, since there is a huge area of low pressure under the car. Air is being sucked out of the engine compartment and completely replaced every few seconds anyway.

Why do you ask?

[Bio}{azard]

Our radiator doesn't seem to be working as well as we need at the moment (210 degrees in 50-60* weather), and can't get a bigger one, so might as well ask about what we can to cool it by other means.

[curtis73]

tell us more about the setup; stock? souped up? electric fans or belt? engine, year, mileage, etc.

Cooling issues are almost always a simple fix, so lets rule out the obvious stuff before adding more airflow.

keep in mind, too, that adding airflow down through the hood will reduce airflow through the radiator and could make things worse. Since almost anywhere on the hood is higher pressure, you'll almost always be removing airflow (a little) from the radiator.

[Bio}{azard]

'74 Vega, '77 231 Buick V6
New cam,
High compression pistons
Four barrel intake manifold
Edlebrock carburator
Single core alluminum radiatior
and duel electric fans
6 months old but it looks like this
http://img.photobucket.com/albums/v6...ard/Engine.jpg

[UncleBob]

Get a fan shrowd on that thing. That'll double your cooling effeciency right there.

That is the most common grevious error people make on cars. Fan shrowds are extremely important for air flow over the radiator.

[Bio}{azard]

Remember, that pic is old, and we now have duel Electric fan and a single core radiator.

[Moppie]

Originally Posted by Bio}{azard

Remember, that pic is old, and we now have duel Electric fan and a single core radiator.

Can you show a pic of that set up?
Are the fans shrouded?
And, does the new single core offer as much surface area as the old one?
Iv seen a few cases were people have replaced an old multicore steel radiator with a new single core all flash and shiny aluminuim one, added lots of fans, and then discovered that the car over heats.
Usualy because all the fans they added to the back inhibbit air flow, or the radiator is to big for the front of the car, and there isn't airflow right accross its front face.
Usualy going back to a smaller multicore radiator solves the problem, as all its surface area is then expose to air flow.

[TheSilentChamber]

Steel radiator eh?

[curtis73]

I don't mean to offend, but I always get a kick out of people who say things like high compression, electric fans, and single row radiator in the same setup.

You need at least a dual core radiator, ditch the electric fans, and how much compression are we talking about?

The electric fans don't move enough air, period. If you are GM with a million dollar R&D budget designing an electric fan to cool a 200-hp stocker, that's different. Then at highway speeds they block more air than they move. Think about it; you took off a belt fan that takes as much as 13 hp to drive and replaced it with twin 1/8 hp motors.

[Moppie]

Originally Posted by TheSilentChamber

Steel radiator eh?

Ok, then, steel frame, top and bottom tanks, with copper fins, all covered in black paint. Feel better?

[Moppie]

Originally Posted by curtis73

Think about it; you took off a belt fan that takes as much as 13 hp to drive and replaced it with twin 1/8 hp motors.

Hmmm, except that belt driven fan used 13hp because of its very ineffcieant design, and while the little electric motors might use less power, they still flow more air at low speed, and when stopped.

A radiator fan is only of any use when the car is stopped, or running at very low speed. Above about 30-40mph they start to become completly useless, and at 60mph they do nothing, if of a poor blade design will infact hamper air flow.
At low speed a belt driven fan dosn't realy move a lot of air because its speed is tied into engine speed. Over gear it to make it more effective and at high engine RPM it ends up turning at dangerous speeds, or simply puts to much resistance on the system.

An electric fan is not worried about engine speed, and so can provide excellent air flow when the vechile is stationary. HOWEVER, a cheap fan is a waste of time, it needs to be a high quality one, and it needs to have a blade design that is able to spin freely in the air flow at speeds above 60mph, or else it will rstrict air flow to much. Also, the thermostat that turns the fan on and off, should be set to come on a little higher than the engines operating temp at speed, so the fan motor is turned off and dosn't inhibbit air flow at high speed.
Usualy when useing electric fans you only cover half the radiator with the fan, and its usualy a fan that is just big enough to cool the engine when the vechile is stationary.
Leave as much as a radiator exposed to free airflow as possible, and let that do the cooling job when traveling at speed.

The radiator needs to be just big enough to fill the open space behind the grill. A bigger radiator won't do anything if its extra surface area is hidden behind body structure, or bumper parts, or headlights etc.
In most cars a smaller 2 or 3 core will cool better than a single core thats twice as big.

[GreyGoose006]

^^^
well put.

[curtis73]

Originally Posted by Moppie

An electric fan is not worried about engine speed, and so can provide excellent air flow when the vechile is stationary. HOWEVER, a cheap fan is a waste of time, it needs to be a high quality one,

I agree with that completely, but we don't know if his problems are stationary or moving.

Typically if its hot on the highway with electric fans, I blame the fans for blocking airflow. If its hot while stationary (where electric fans do their best work) I suspect not enough fan.

Either way in this case, I feel strongly that its the electric fans. When someone says "overheat" and "electric fan" in the same sentence its almost always the culprit. Either they're restricting air flow on the highway, or they're not providing enough flow while stationary.

Of course the single row radiator doesn't help either. Bio.. you could have a three-core copper brass radiator built from scratch for about $400. They would use GM tanks and a good Modine high-efficiency core and it would cool MUCH more efficiently than your single core aluminum.