If you read all of this you will find some interesting, very relevant things, especially near the end.
Just so you know, I'm actually from northeastern Oklahoma. Where we get a lot a rain.
I'm just stationed down here. When it rains, it pours.
Tornadoes Too!
I've watched some really big thunder/lightning storms moving into central Oklahoma when I was there, observed from flat land to the horizon, spotted from long distances and fascinating to watch. I've been such a weather freak in the past I learned the National Weather Service acronyms used for airline pilots and I watched their (airport) Doppler Radar nearly every early morning to calculate what time storms would arrive. I had to know how to schedule the work at a construction site.
Later, I often watched severe storms on Doppler and learned how to spot possible tornado formations. I got pretty good at predicting where they would form. I nailed a few right on the money! I knew your N.E. Oklahoma area well on Doppler Radar because I had a girlfriend living across the border in Arkansas and always watched the tornado producing storm cells to give her some warning to go in the shelter. She lived in a Mobile Home. She always said, "I AIN'T GOIN' DOWN THERE!!" "TOO MANY SNAKES!!"
As was pointed out earlier, the intake seal is actually the more important piece. If water can get in, dirt/dust can get in. I don't know about you, but I'd rather not trash my engine like that.
While the hood seal is important, it's not the root of the problem, is all I'm getting at.
I do understand your viewpoint. Lets just say that
all seals are important.
A point that I want to make very strongly is that with an air cleaner with a deep dish, you can NOT SEE the seal. A mirror wont work to inspect it and it is (as I think I've described) a real pain in the - (PITA) to remove and replace in order to inspect the seal. It's
something I only want to do when I change the air filter which could be a very long time between filter changes. Likewise, how many people bother to inspect the small seal on a stock air cleaner? Again, only when they change the filter, if even then!
By comparison, the hood-to-cowl seal is large, very visible and very easy to inspect for cracks
any time the hood is opened- no work at all, really, just put my fingers on it and look. It's also something easy to remember and be reminded of because it is so large and visible. If that doesn't leak we are A-OK for water!
Personally, I have never been concerned with dust and 'dirt' coming through a cracked seal at the screw-down (usually wing nut) on top of an air cleaner and I drove on many hot dusty gravel roads during the summer and have had my engine compartments full of gravel dust many times. I had to blow off the dust on occasions to check if the air cleaner needed to be changed.
Lets assume 4 or 5 tiny cracks in THAT seal. I would estimate that about 99.999xxx if not 100 percent of the air flow is coming directly through the air filter which should have very low resistance when it is good and not plugged up.
Further, in my perceptions (knowing a bit about behavior of air under various positive and negative pressure (or vacuum) conditions including with wind speeds around various structures and shapes) I perceive that there is
very low vacuum in the air cleaner to pull any air or dirt through cracks if they do in fact go all the way to the center and into the air cleaner
because the air being pulled into the manifold is very efficiently replaced by air coming through the huge surface of the air filter with very little resistance.
HOWEVER, WATER WILL ALWAYS go through those cracks, engine running or not and additionally there is the wicking effect which will pull water through tiny cracks. Left for long enough (days of rain) with a leaking hood-to-cowl seal these small cracks could result in enough water entry to cause a hydro-lock in a cylinder. I've never experienced it and don't want to. A tiny air leak is not going to create an air and dust lock in a cylinder.
If I had a standard air filter and if my truck was running now (lots of stuff apart in engine compartment) I would go outside and use a vacuum gauge to see how much vacuum is present at that hole to get a better idea of what is truly happening at that location. (idea: vacuum sensor to Idiot Ding-Ding Light on instrument panel: "Ding-Ding" then woman's voice...
"Your Air Filter is Ready to be changed, would you like me to change it for you?" Yeah, yeah, it's ready! Then...
"Here is a map to your nearest Ford Service Center, Ding-Ding" Darn-it! That was a good dream for awhile...
I suspect that any vacuum reading being enough to show on the gauge would indicate that the filter is dirty and any significant vacuum would mean that the filter is dirty enough to bog down the engine.
BUT WAIT! Special deal here for reading this far (thank you) One more better special deal #2 for everyone, further below! So, THAT (small cracks)
is not what you are talking about! (I pretty much knew that). You are talking about a very damaged seal or NO SEAL. THAT is a very legitimate concern,
especially for water coming down from a leaking hood-to-cowl seal
because it does not take much water to cause a hydro-lock in a cylinder AND this can happen with engine not running (parked over night in a heavy rain). While driving in the rain it might be similar to a diesel water injection system BUT DO NOT TRY THIS.
YES it is also a concern for dust and dirt entering the intake when the engine is running- especially on dusty roads. Very much something we want to AVOID AT ALL TIMES.
That being said, it doesn't matter what I said at all (or did not said),
ALL SEALS ARE IMPORTANT or they would not have been created and further, there are a few
seals that should have been created that were not created.
Special deal number 2:
That leaves us with room to create more improvements for our trucks. I am wondering what other seals would be beneficial and need to be created?
What about hood to fender water/dust seal and extra benefit of noise reduction!? WOW, check this out! Looking at the first photo I posted, under the hood passenger side, there is a wet spot (rain water) and some green stuff on the fender by the mounting bolts. Green stuff is probably tree pollen.
Look and see! An easy to install seal could run along the fender all the way back to the back end of the cowl. (keep in mind that my cowl is not adjusted and is dipping down- it should be flush with the top of the fender). THEN the longer hood-to-cowl seal that I proposed earlier could "tie in" to the fender seal and drainage into the engine compartment would be SOLVED! Also sealed from dust, dirt, debris from trees, etc.
This 'tie-in' of the two seals should be fairly easy to figure out and can be improved with time.
Finished for tonight. (2:45 AM)