[leeklm]

Helping a buddy with highway heating issues in his 66 Abody. He forwarded an article from another pontiac site that was suggesting the lack of splash guards over the a-arms would disrupt airflow to the point of reducing air coming in past the radiator. Claims to have reduced highway engine Temps by reinstalling the splash guards.

I really have a hard time believing the lack of splash guards would have this effect when driving down the road 60+ mph.

Anyone ever hear this theory??

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[ZeGermanHam]

I call hogwash. There is no engine compartment undertray like modern cars have, so absence of the splash guards isn't going to make a bit of difference in that regard.

My '66 didn't have the splash guards before I took it apart, and driving 55-60mph was when it ran the coolest.

[Schurkey]

I heard that years ago, along with the need for the rubber seal at the back of the hood.

First Guess: That's why GM put them there.

[ZeGermanHam]

Originally Posted by Schurkey

I heard that years ago, along with the need for the rubber seal at the back of the hood.

First Guess: That's why GM put them there.

If I was a betting man, I'd say GM put those items there to prevent the firewall electrics, distributor, and spark plugs from getting water on them. Don't think they have anything to do with airflow.

[Jerry H.]

I think someone was confused and was referring to the 'splash' guards around the radiator on a car equipped with factory air.

[Tom Vaught]

Originally Posted by Jerry H.

I think someone was confused and was referring to the 'splash' guards around the radiator on a car equipped with factory air.

I agree with Jerry, having spent time in the Lockheed with tunnel doing smoke tests on my company's vehicles. A pic of smoke testing vehicles.

Tom V.

[leeklm]

Originally Posted by Jerry H.

I think someone was confused and was referring to the 'splash' guards around the radiator on a car equipped with factory air.

Agreed, that does make a lot more sense!

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[Radman]

Easy way to check which way the air is going. Take a 3 inch thread and some scotch tape. Tape the thread down with about 1 inch sticking in the hole you are interested in, and the rest of the tape in a loop that is free. Drive the car at about 30 MPH stop and check the thread. Then drive the car at highway speed, and check the thread again. I will bet that the air goes out toward the wheel well.

[Tom Vaught]

Since everyone has phones these days, rig up a "mount" so that you can actually watch the thread movement as the car is being driven (when you play back the video).
Same deal at the higher speed. You might be surprised at the difference in your original assumptions (because the air moves in one manner at lower speeds, possibly has a different manner at higher speeds, and returns to the original manner so you get back to the lower speeds).

Food for thought

Tom V.

[SRR]

If it's heating up on the highway he has a coolant flow problem not an air flow problem.

[Scarebird]

Originally Posted by ZeGermanHam

I call hogwash.

schweinen waschen?

sorry, watching "Babylon Berlin" on Netflix and my rusty high school German kicks in...

I would think that the flaps would impede airflow, not help. My Trans Am and Lemans both have fender extractors for this exact reason.

[leeklm]

Originally Posted by SRR

If it's heating up on the highway he has a coolant flow problem not an air flow problem.

Agreed. Next step is to check propeller clearance on the flowcooler pump, and possibly try a smaller pulley

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[HWYSTR455]

Vacuum advance also helps highway speed cooling. If you run manifold vac source it helps with idle cooling too.




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[ta man]

You always need an exit for the underhood air..otherwise it builds up air pressure and heat. I agree they were just splash shields to keep water out of the engine compartment.

[Schurkey]

The "exit" is under the car. It's a natural low-pressure area so the heated radiator air naturally blows downward and out.

Remove the seal at the rear of the hood--which is a high-pressure area, as evidenced by the various forms of "cowl induction"--and you have additional air trying to go "down and out". Every bit of air seeping into the engine compartment from the back of the hood is that much less air coming in through the radiator. Note that all the "factory" applications of cold-air induction have seals to prevent that "cold" air from entering the engine compartment--all that air is ducted to the carb, but not to the engine compartment at large. A lesson that 90% of the hot-rodders entirely failed to grasp.

I'm less-sure of the fender seals. I don't know how the rotating tires affect air pressure in the inner fender--high pressure or low pressure. Therefore I don't know whether engine compartment air is being added or subtracted when the seals are removed.

An air-dam under the radiator support makes a big difference in cooling, because it builds pressure ahead of the radiator, and reduces pressure behind the radiator--which means considerably increased air pressure drop across the rad, and therefore more air flow.

[brjgto]

I have worked in Aerothermal for over 20 years in a Big 3 OEM. These “”splash guards” are just that, for splash. There is adequate room for airflow in a 1960’s style car of any type. Look at the frontend, radiator and shrouding. Shrouding should be close to the fan, but not past the fan. Later cars have air dams for highway cooling. You might want to consider this if your radiator is flowing ok.

[HWYSTR455]

Originally Posted by Schurkey

The "exit" is under the car. It's a natural low-pressure area so the heated radiator air naturally blows downward and out.

Remove the seal at the rear of the hood--which is a high-pressure area, as evidenced by the various forms of "cowl induction"--and you have additional air trying to go "down and out". Every bit of air seeping into the engine compartment from the back of the hood is that much less air coming in through the radiator. Note that all the "factory" applications of cold-air induction have seals to prevent that "cold" air from entering the engine compartment--all that air is ducted to the carb, but not to the engine compartment at large. A lesson that 90% of the hot-rodders entirely failed to grasp.

I'm less-sure of the fender seals. I don't know how the rotating tires affect air pressure in the inner fender--high pressure or low pressure. Therefore I don't know whether engine compartment air is being added or subtracted when the seals are removed.

An air-dam under the radiator support makes a big difference in cooling, because it builds pressure ahead of the radiator, and reduces pressure behind the radiator--which means considerably increased air pressure drop across the rad, and therefore more air flow.

This is right on target, and as for 'fender air extractors', it's to direct and relieve the build up of underhood/under-body psi to prevent/control front end lift at higher speeds. (i.e. - higher psi)

I believe most of the air travels across the side of the fender and underside/over top of the body, and with a little more psi from the underhood at slower speeds, due to frontal area, it probably forces more air out the wheelwells to the outside of the car. But just using reason, I have no factual data on it. Could probably look at some wind tunnel vids and figure it out though.

As for 'seals', obviously you want to control the frontal area air flow, and force as much as possible thru the rad core. So those seals are important, and in some cases, required. Without them, you can actually suck hot air from the engine compartment thru the core.

Air dams direct air not just thru the core, but also help lower undercar air psi, allowing less of a buildup, which not only helps with airflow thru the core, but helps control body lift as well. Depending on the size and effectiveness, an air dam can actually provide additional front end downforce, aiding in better overall airflow and planting the front tires better.


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[Tom Vaught]

On John Clegg's 64 GTO with the LARGE Vortech Supercharger and the Air to Air inter-cooler he was getting lots of air to the inter-cooler thru the grill and bumper but the radiator was suffering from a lack of cool air due to the air from the inter-cooler raising the air temp the radiator saw.

So I had John install an Air Dam under the bumper that kept some air from getting underneath the car and slowing down the 200 mph Texas Mile attempts AND we added a bunch more clearance between the inter-cooler and the inlet to the radiator.
Now the air from the Air Dam goes BETWEEN the Inter-cooler and the Radiator, pushed upward the hot air away from the inter-cooler/Radiator space, adds cool air from the outside of the vehicle to the radiator and the Speeds went up and the cooling improved for both the Inter-cooler and the Radiator. Food for Thought.

So my point is figure out what the air under the hood is actually going, Figure out if your current system is adequate for cooling the vehicle, Don't assume that you know how air moves thru a engine compartment until you do some
actual testing at speed with a phone camera on the roof pointing at the hood. (helps a lot with air scoop design).
Put the phone camera under on the inner fender and look at how the air flows to the air cleaner again using wool
String "Tufts" to see the airflow there.

Tom V.

[brjgto]

Originally Posted by Schurkey

Remove the seal at the rear of the hood--which is a high-pressure area, as evidenced by the various forms of "cowl induction"--and you have additional air trying to go "down and out". Every bit of air seeping into the engine compartment from the back of the hood is that much less air coming in through the radiator. Note that all the "factory" applications of cold-air induction have seals to prevent that "cold" air from entering the engine compartment--all that air is ducted to the carb, but not to the engine compartment at large. A lesson that 90% of the hot-rodders entirely failed to grasp.
.

The hood seal is for not breathing under hood air from your HVAC. Nothing to do with cooling. Cowl induction is a different matter all together..

[Schurkey]

Originally Posted by brjgto

The hood seal is for not breathing under hood air from your HVAC. Nothing to do with cooling. Cowl induction is a different matter all together..

The hood seal has two purposes
1. Prevents under-hood air/oil fumes from leaving the engine compartment and smelling-up the HVAC when stopped or at at low speed, and

2. Prevents high-pressure cowl air from entering the engine compartment, interfering with air coming through the radiator at high speed.