Cat 3116 engine swap into blue

not a chance. I will have my belly full, and a headache with the project ahead already. No need for further complications. Snakeater

Basically you got it snakeater...the hood vents allow for more air flow through the compartment and reduce underhood temp a lot.

that may very well be something that has to happen. My engine bay will be pretty full. It may require it to cool correctly, i will go ahead and start planning for that. what about venting out of the fender area between wheel well and the firewall? Not as effective? Snakeater

Dont know that anyone has done that...

I think people have worked with the heat rises so cut at the top AND less restriction to airflow means more flow so top seems it would flow better.

Cant hurt the aerodynamics much either way really... :)

these trucks have aerodynamics? Cool one less thing to worry about.......:DSnakeater

Along the lines of letting hot air out, there is a lip on the left and right side of the hood, which sort of slots into the fenders.

Some folks over on IFSJA have reported success, by bending it up flat, and allowing air out between the fenders and hood. Can't say for sure how it works, as I have never tried it, but it looks promising. Figure it would amount to an 1/8" gap, roughly 3 feet long, on either side.

The deuces all have louvers in the inner fender wells. Maybe for extra cooling?

Thanks Jon, you are right of course. It was Barry (anyone here with that truck that could post pics?). Tom had that little scoop facing the windshield.
As for the vents up top I would thing it is more of an air flow management thing than just hot air rising. The air should be moving along too fast for that to matter. You could skid plate the entire area under your motor/trans and put a couple of air deflectors at the back to cause a vacuum - literally sucking the air out of the engine bay :)

The vent on top works with rising heat when at idle...at speed, it is just a convenient place for air coming in the front to get out...short straight path...like an intake port should be...

OK, I'll give you the at idle thing, but I really like the skid plate/ vacuum thing. Why, once you hit 80 or 90 and that... Oh, I just thought of a problem :) lol
Louvering the inner fender doesn't work so well from what I've heard. Great idea to keep the exterior sheet metal looking stock though. I was never sold on Barry's cowl vent idea. I seem to remember that he was happy with the result, but the idea of a cowl vent is to let air INTO the engine compartment, not out. Again, this is assuming a much higher average speed than a 715 would normally achieve.

Dahoyle would you have a pic of that. I understand what you are saying, I just cannot picture it in my head.